FOUS30 KWBC 270801
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
401 AM EDT Wed Aug 27 2025

Day 1
Valid 12Z Wed Aug 27 2025 - 12Z Thu Aug 28 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE CENTRAL PLAINS & NORTHWEST...

...Central Plains...

A sheared 500mb vort max exiting the Central Rockies will spawn a
surface low over the southern High Plains today. Working in tandem
with a dome of high pressure to the east, this will tighten the
pressure gradient and prompt a strengthening LLJ to form over the
Southern Plains late Wednesday afternoon and into Wednesday night.
This enhanced LLJ will not only act to deliver rich Gulf moisture
northward, but it will also cause 850mb frontogenesis to ensue over
the Central Plains. PWATs will surge to 1.8-2.0" within the Slight
Risk area with MUCAPE ranging between 500-1,000 J/kg. These
parameters would support up to 2.5"/hr rainfall rates within storms
that could contain mesocyclones. This is due to vertical wind
profiles that sport 30-40 knots of sfc-6km shear and sfc-1 km SRH
values in excess of 200 m/2 s/2. These vertical wind shear values
support mesocyclone formation, which are efficient rainfall
producers within environments containing deep warm cloud layers and
highly saturated sfc-500mb environments, all of which apply in
this situation. The latest 00Z HREF has started to show some higher
confidence in southeast KS in being the epicenter of the heaviest
rainfall. 24-hr QPF probabilities for >3" of rainfall are high
(70-90%) and probabilities for >5" are now 30-45%. While confidence
in locally significant rainfall amounts are increasing, the
placement still remains lower in confidence. With the bulk of this
event unfolding between 06-12Z Thurs, opted to hold off on a
categorical risk upgrade tonight to see if new 12Z HREF guidance
provides more supportive insight into the Wednesday night flash flood setup.

Meanwhile the Slight Risk area in the Central High Plains and along
the Front Range of the Rockies remains in place. Many locations now
sport overly saturated soils, as shown by the NASA SPoRT-LIS 0-40cm
soil percentiles which are above the 90th percentile. PWATs remain
above the 90th climatological percentile and anywhere from
500-1,000 J/kg of MUCAPE will provide sufficient instability to
support up to 1.5"/hr rainfall rates along the Front Range, and
perhaps as high as 2"/hr in the CO High Plains. The Slight Risk
remains in place due to the combination of anomalous moisture and
modest instability triggering storms over areas that feature
sensitive soils.

...The West...

There remains no shortage of monsoon moisture throughout much of
the West, but the focus for flash flooding will become more
pronounced in the Northwest. An organized 700mb low will have an
abundance of moisture in place from OR/WA on east into the northern
Rockies. PWATs from the Blue Mountains and Snake River valley on
east across the Bitterroots and into southern MT/western WY are
likely to top the 99.5 climatological percentile and the presence
of the 700mb low will provide additional synoptic-scale support. In
addition, modest instability for the region will be present with
the ECMWF-EFI showing a pronounced signal for unusually high CAPE
(or instability) values across the northern Great Basin, eastern
OR, and much of ID. The same tool (ECMWF-EFI) depicts an impressive
QPF footprint over much of eastern OR, southern ID, northern NV,
and into much of WY. Sufficient instability (500-1,000 J/kg
MUCAPE) is also present for storms to tap into from the northern
Great Basin on north into the Northern Rockies to justify rainfall
rates that approach 1.5"/hr. The Slight Risk remains on track given the forecast remains largely unchanged, and thus provides additional confidence
in the flash flood potential in the Bitterroots, Tetons, and Snake
River Valley today and into this evening.

Mullinax


Day 2
Valid 12Z Thu Aug 28 2025 - 12Z Fri Aug 29 2025

...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE CENTRAL PLAINS, CENTRAL ROCKIES, & LOWER MISSISSIPPI VALLEY...

...Central Plains & Lower Mississippi Valley...

A 500mb vorticity maximum tracking towards the Ozarks on Thursday
will work with the diffluent right-entrance region of a 250mb jet
streak to provide excellent upper-level ascent over the Lower
Mississippi Valley. Further supporting the synoptic-scale forcing
over the Southern Plains and Lower Mississippi Valley is the
GFS/ECMWF showing 700mb Q-vector convergence over the region. This
is all occurring in the same area where low-level WAA is occurring
amidst WSW flow into a warm front that will meander around the
ArkLaTex on Thursday morning. This WAA will also usher in rich Gulf
moisture into the region that increases PWATs to 2.0-2.25"
throughout the Southern Plains and Lower Mississippi Valley. There
is also no shortage of instability, highlighted by a plume of
1,000-2,000 J/kg of MLCAPE for storms to work with. Given these
parameters, maximum rainfall rates could range between 2.5-3.0"/hr
within the most intense thunderstorms. These storms will also have
sufficient vertical wind shear (35-45 kts) and low-level SRH above
200 m2/s2, fostering mesocyclones within some thunderstorms just
north and east of the warm front. All these factors support the
potential for flash flooding within the Slight Risk area. Aside
from minor tweaks based off latest WPC QPF trends, no significant
adjustments were made this forecast cycle.

...Intermountain West...

A large pool of monsoonal moisture remains anchored over the
Rockies and Great Basin, highlighted by PWATs that are routinely
above the 90th climatological percentile in these regions. The
Northern Rockies will still have the lingering 700mb low over the
region that helps provide modest upper-level ascent to support
developing thunderstorms. Farther south, the Central Rockies are
located at the nose of a 250mb jet streak and low-level convergence
along the Front Range will foster widespread thunderstorms. Soils
will continue to saturate further in the days leading up to
Thursday over the Northern and Central Rockies that will further
exacerbate the flash flood threat. A Slight Risk is in place over
the Central Rockies that spills over into the the central High
Plains given the higher PWATs and instability in the region,
coupled with the gradually moistening soils. Given the lingering
spread in guidance regarding the placement of the strongest
thunderstorms, a Slight Risk was not issued as of this forecast
cycle. Should confidence increase in both heavier totals and
placement, and should antecedent soil moisture conditions continue
to grow more sensitive following Wednesday's rainfall, a
categorical risk upgrade may be necessary.

Mullinax


Day 3
Valid 12Z Fri Aug 29 2025 - 12Z Sat Aug 30 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER A LARGE
PORTION OF THE GREAT PLAINS, THE FRONT RANGE OF THE ROCKIES, AND
ACROSS MUCH OF THE DEEP SOUTH...

A pool of anomalous atmospheric moisture will maintain a
stronghold over the Northern Rockies and Plains on south through
the Southern Plains. A series of 500mb disturbances exiting the
Great Basin will provide some upper-level support for thunderstorms
from the northern Rockies and Plains on south to the Central
Rockies Front Range and Plains. Farther south, a nearby frontal
boundary in the southern High Plains will be the primary trigger
for thunderstorms. This area will have a greater concentration of
PWATs to work with (1.3-1.5" in the TX/OK Panhandles into eastern
NM) and greater MLCAPE values (topping 1,000 J/kg). These areas
will have seen soils dry up following a couple days of drier
weather, and given some global guidance members differ on the
location of the storms, there was no categorical risk upgrade this
forecast cycle.

Farther east, a wave of low pressure will track east along a
frontal boundary that stretches from the Front Range of the
Rockies to Florida. Numerous showers and thunderstorms are likely
to envelope the South, with the Lower Mississippi Valley favored to
see the heaviest rainfall at this time. Guidance shows the Lower
Mississippi Valley sporting the highest PWATs (2.0-2.25") and
instability (MLCAPE 1,000-2,000 J/kg) while also being more
favorably located closer to the emerging area of low pressure in
eastern TX. The GEFS/GEPS camps favor the Lower Mississippi Valley,
but many ECMWF members were still showing storms that could
produce locally heavy rainfall as far east as eastern GA. Given the
lingering spread in model guidance, and the Lower Mississippi
Valley's currently higher 1-3hr FFG exceedance values, there was no
categorical risk upgrade hoisted as of this forecast cycle. But
the >2.0" PWATs and modest instability does support a localized
flash flood threat across much of the South during a time that also
just so happens to be the kickoff to Labor Day weekend. Flash
flooding could result in some locally hazardous travel conditions,
especially along roads that drain poorly.

Mullinax
$$
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FOUS30 KWBC 280825
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
425 AM EDT Thu Aug 28 2025

Day 1 Valid 12Z Thu Aug 28 2025 - 12Z Fri Aug 29 2025

...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE CENTRAL ROCKIES AND THE SOUTHERN PLAINS INTO THE LOWER
MISSISSIPPI VALLEY...

...Southern Plains into the Lower MS Valley...
Convection will be ongoing at 12z this morning across portions of
southeast KS, northeast OK and into central and northern AR. Some
northwest to southeast training of convection is expected, and
scattered instances of flash flooding will probably be ongoing and
continue into the morning hours. Instability is a limiting factor,
and interesting to note that the 05z HRRR has significantly less
CAPE at 12z than the 00z HRRR and other 00z HREF members. This
downward trend in instability during the morning hours should
limit the coverage and magnitude of the flash flood risk from
eastern OK into AR...however convection should still train enough
to produce isolated to scattered flash flooding, especially over
any more susceptible areas, with amounts of 2-4" still probable.

By later this morning into the afternoon hours indications are
that convection should begin to forward propagate off to the south,
picking up speed as it pushes into and through southern AR.
Instability should be on the increase by this time resulting in
higher rainfall rate potential, but the expected quicker cell
motions should still cap the flash flood risk in the isolated to
scattered range.

Another uptick in convection is likely Thursday night into Friday
morning as low level convergence increases. More uncertainty with
the details by this time, but an area of expanding backbuilding
convection could develop over the ArkLaTex during this timeframe,
potentially driving and increased flash flood risk.

Model QPF forecasts are getting to the level of MDT risk
consideration. However do note that HREF probabilities of exceeding
3hr FFG do not get much above 25%, and probabilities of this
magnitude are not widespread. Typically we see higher HREF FFG
exceedance probabilities in MDT risk level events. The high FFG
over much of the area is likely the primary driver of these lower probabilities, however the aforementioned lower instability in
place this morning is also likely to keep rainfall rates a bit
lower and thus less likely to exceed FFG on a more
numerous/widespread basis. Nonetheless will need to continue to
closely monitor model/observational trends today. At the moment,
the activity tonight into Friday morning over the ArkLaTex seems to
have the better chance of reaching MDT risk levels, especially if
rainfall this afternoon is able to lower FFG ahead of what should
be an uptick in backbuilding/training tonight into Friday morning.
Not enough confidence in the details to go MDT, but still think
higher end Slight risk probabilities are justified across portions
of eastern OK into western AR, far northeast TX and far northwest LA.

...Rockies and Western U.S....
A small Slight risk was maintained across portions of southeast
CO. With easterly upslope flow into the Front Range high res models
indicate convective initiation this afternoon, with cells moving
eastward into the CO Plains, before diving off to the south. Some
initial slow cell motions and the possibility of a cell merger or
two will allow for areas of locally heavy rainfall. Most models
really only indicate one or two stronger cells persisting long
enough to drive a flash flood risk...so there is a question whether
the coverage of flash flooding will reach Slight risk levels. But
given the risk is already out, and the fact that models continue
to show a focus for heavier rainfall amounts over this corridor, we
opted to maintain the Slight risk.

Elsewhere a broad Marginal risk covers much of the Intermountain
West. Not expecting as much coverage of convection or as heavy of
rainfall totals as we saw on Wednesday, but localized areas of
heavy rainfall remain possible within the Marginal risk area. The
best convective focus will likely be across portions of
southern/central MT and northeast WY, but only modest instability
should keep rainfall rates down enough to keep any flash flood
risk isolated in nature.

Chenard


Day 2 Valid 12Z Fri Aug 29 2025 - 12Z Sat Aug 30 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER EASTERN NEW
MEXICO INTO THE TEXAS PANHANDLE, AND OVER PORTIONS OF THE LOWER
MISSISSIPPI VALLEY AND SOUTHEAST...

...Lower MS Valley into the Southeast...
The mesoscale and synoptic features responsible for the day 1
convection over the Southern Plains and Lower MS Valley will shift
southeast on Friday. More model spread is noted by this
time...with the 00z GFS remaining an outlier. The GFS continues to
be more suppressed and weaker with this feature than the other
global model guidance. The ECMWF, CMC, UKMET, ICON and NAM are all
farther northeast with the heavy rainfall axis stretching into
portions of MS and AL than the GFS is. The AIFS and both the ECMWF
and GFS initialized Graphcast are also farther northeast than the
GFS. Thus, it seems more likely than not that the GFS is too
suppressed and it represents a less likely outcome at the moment.
The ECMWF has been the most aggressive with a farther northeast
axis, but do note that is has been gradually trending southwest the
last few runs...and so the ECMWF may be a bit too far northeast.

Given the above model diag, it seems prudent to go ahead with a
Slight risk across portions of the region. The environmental
ingredients will be conducive to heavy rainfall, with PWs over 2"
and a corridor of persistent lower level moisture
transport/convergence supporting some backbuilding and/or training
potential. Other than the weaker GFS, models show an area of low
pressure only slowly moving eastward along a low level frontal
axis...with upwards of 2000 j/kg of CAPE near and south of this
boundary. Thus it does seem like an excessive rainfall threat
could evolve Friday into Friday night with either a persistent
swath of convection or multiple convective rounds. The Slight risk
area was drawn from portions of central/northern LA into
central/southern MS and southwest AL...as this corridor is
generally the consensus axis of heaviest rainfall potential from
the non-GFS solutions. The high FFG keep this as just a lower end
Slight risk for now, and I would expect to see some adjusting of
the risk area as we get closer and models better converge on a solution.

...Rockies into the High Plains...
A Slight risk was also added for eastern NM into the TX Panhandle.
We should see an uptick in both CAPE and PW compared to Thursday,
and a shortwave feature and upper jet on the northern periphery of
the upper level ridging will help initiate convection Friday
afternoon. It also looks like some mid/upper level moisture
streaming well north and east of Juliette in the Eastern Pacific
will move into these areas Friday, likely helping increase rainfall
efficiency. High res models indicate convection initiating over
eastern NM near higher terrain Friday afternoon, before propagating
off to the east. Cell motions look rather quick off to the east,
which may end up limiting the extent/magnitude of the flash flood
risk. However it looks like enough of a surge in instability and
PWs to suggest high rainfall rates, and we could be looking at
enough convective coverage to support some upscale convective
cluster development. So there seems to be enough there to justify
going with a Slight risk over these areas.

Elsewhere, areas of convection across portions of NE into SD and
MT will pose a localized flash flood risk. Convective coverage and
intensity here also looks higher than Thursday, and can not rule
out eventually needing another targeted slight risk area, but for
now even with the greater convective coverage, any FFG exceedance
looks isolated in nature.

Chenard


Day 3 Valid 12Z Sat Aug 30 2025 - 12Z Sun Aug 31 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM EASTERN NEW
MEXICO INTO WEST TEXAS...

...Rockies into the Plains...
Mid/upper level riding will gradually breakdown by Saturday over
the Plains resulting in increased troughing and embedded shortwave
energy. This should drive rather widespread convection from TX/NM
all the way into the Dakotas. A Slight risk was maintained from
eastern NM into the TX Panhandle and west central TX where the
ingredients appear better for an excessive rainfall threat. This
area will see an uptick in instability compared to Friday, with
PWs also trending slightly higher and well within the range of
supporting heavy rainfall rates. The right entrance region of an
upper jet and an increase in low level moisture transport Saturday
evening support an organized convective threat. Convective details
this far out are uncertain, but the overall pattern supports
terrain driven convection over NM growing upscale as it moves
eastward into western TX resulting in an isolated to scattered
flash flood threat.

...Southeast...
More uncertainty exists over the Southeast by Saturday. As was
described in the day 2 discussion, still think the 00z GFS is an
outlier and lower probability solution. Most other models indicate
a lingering frontal boundary with a low and enhanced moisture
transport. Thus it seems more likely than not that at least
localized areas of heavy rainfall will remain possible from the
Gulf Coast and possibly into portions of GA and SC. The northern
extent of this risk is more uncertain, and quite possible the 00z
ECMWF (and other recent ECMWF runs) is too far north and east. But
somewhere from the central Gulf Coast into north FL and southern
GA still looks in play for heavy rainfall Saturday into Saturday
night. The overall environmental ingredients would support Slight
risk level rainfall...however the combination of high FFG and
above average uncertainty suggests sticking with a broad Marginal
risk is the best course of action for now.

Chenard
$$
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FOUS30 KWBC 290820
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
420 AM EDT Fri Aug 29 2025

Day 1
Valid 12Z Fri Aug 29 2025 - 12Z Sat Aug 30 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER EASTERN NEW
MEXICO INTO THE TEXAS PANHANDLE, THE NORTHERN/CENTRAL PLAINS, AND
OVER PORTIONS OF THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST...

...Lower MS Valley into the Southeast...

Conditions will be favorable across the Lower Mississippi
Valley/Gulf states for convection to backbuild and/or train. PW
values around 2 inches will be pooled over the region as an area of
low pressure slowly propagate along a frontal boundary.
Considering the environmental factors and deep layer ascent, there
will surely be areas that see > inches of rainfall during the
forecast setup with modest neighborhood probabilities for >5 inches
(20-35%) situated across the aforementioned areas. Higher FFG's
will curb the top end of any threat as the recent dry pattern has
relegated all 1/3/6 indices to run very high, a state that usually
leaves significant flash flood potential muted historically. The
Slight Risk will likely be a low end threat and spans from far
eastern Texas to central Alabama.

...Rockies into the High Plains...

A shortwave feature and upper jet on the northern periphery of
the upper level ridging will help initiate convection during the afternoon.
It also looks like some mid/upper level moisture streaming well
north and east of Juliette in the Eastern Pacific will move into
these areas, likely helping increase rainfall efficiency.
Hi-res solutions continue to depict convective initiation near the
higher terrain of eastern New Mexico during the afternoon hours
before progressing swiftly eastward during the evening and
overnight hours; this may limit the magnitude of the flash flood
risk. However it looks like enough of a surge in instability and
PWs to suggest high rainfall rates, and we could be looking at
enough convective coverage to support some upscale convective
cluster development. The Slight Risk area was maintained with minor
reshaping to reflect the latest trends and WPC QPF.

Further north, areas of convection across portions of
Nebraska, South Dakota and Montana will pose a localized flash
flood risk. Guidance continues to focus the greatest amounts from
south-central South Dakota to southern Nebraska, noting an uptick
in activity and amounts from previous runs. A Slight Risk was
raised for an increased threat for localized flooding concerns.

...Northeast...

Convection along a slow advancing frontal has the potential to
produce very localized 1-3 inches along the I-95 corridor, with
the greater potential focusing across portions of New Hampshire and
Maine. A Marginal Risk area was raised from eastern
Connecticut/Rhode Island north/northeastward to central Maine.

Campbell/Kleebauer/Chenard


Day 2
Valid 12Z Sat Aug 30 2025 - 12Z Sun Aug 31 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM EASTERN NEW
MEXICO INTO WEST TEXAS AND ACROSS THE PLAINS...

...Southeast...

During this period convection will focus near a lingering frontal
boundary with a surface low and enhanced moisture transport. Thus
it seems more likely than not that at least localized areas of
heavy rainfall will remain possible from the Gulf Coast and
possibly into portions of Georgia and South Carolina. The best
threat would be for urban areas since local FFG are high across the
region. The northern bounds of the Marginal Risk was lifted
northward to include more of central Georgia.

...Rockies into the Plains...

Increased troughing and embedded shortwave energy is expected
during this period as the upper level ridging breaks down. This
may result in widespread convection to develop and spread out
across the Plains. The Slight risk was maintained from eastern New
Mexico into the Texas Panhandle and west-central Texas where the
alignment of increased instability and higher PW values are better
for an excessive rainfall threat. The right entrance region of an
upper jet and an increase in low level moisture transport Saturday
evening support an organized convective threat. This pattern
supports terrain driven convection over New Mexico growing upscale
as it moves eastward into western Texas resulting in an isolated to
scattered flash flood threat. The Slight Risk that was already in
place was maintained with only a minor expansion of the eastern
bounds over central Texas.

A Slight Risk was raised for this period parts of South Dakota,
Nebraska and Kansas as the area of convection in the Day 1 period
advances eastward along and ahead of the propagating front. Much
of the guidance show areal averages of 1 to 3 inches with local
maxes of 4+ possible.

Campbell/Chenard


Day 3
Valid 12Z Sun Aug 31 2025 - 12Z Mon Sep 01 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM SOUTHERN NEW
MEXICO INTO WEST TEXAS...

Heavy rainfall will continue to focus along a draped frontal
boundary from the Southern Plains to the South East. The moist
monsoonal flow along with embedded shortwave energies traversing
the flow will help enhance rainfall amounts, particularly over
southern New Mexico and West Texas where a Slight Risk for
excessive rain persist. A broad Marginal Risk spans from eastern
Arizona to the Southeast Coast.

Convection ahead of the front in the Plains will continue to pose
an elevated threat for excessive rainfall. A Marginal Risk was
carried over from yesterday's Day 4 period.


Campbell
$$
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FOUS30 KWBC 300805
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
405 AM EDT Sat Aug 30 2025

Day 1
Valid 12Z Sat Aug 30 2025 - 12Z Sun Aug 31 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM EASTERN NEW
MEXICO INTO WEST TEXAS AND ACROSS THE PLAINS...

...Rockies into the Plains...

Increased troughing and embedded shortwave energy is expected
during this period as the upper level ridging breaks down. This
may result in widespread convection to develop and spread out
across the Plains. An axis of high QPF values is expected to set up
from far eastern New Mexico east towards the Dallas/Fort Worth
area, which will be the area with the highest potential for flash
flooding, especially near steep terrain and burn scars. This
pattern supports terrain driven convection over New Mexico growing
upscale as it moves eastward into western Texas resulting in an
isolated to scattered flash flood threat.The Slight Risk area was
maintained for this part of the region. Elsewhere, the broad
Marginal was maintained across much of the Plains and for portions
of the Gulf Coast and Southeast. There was an uptick in QPF amounts
and coverage across portions of eastern Texas which warranted an
eastern nudge of the Marginal Risk.

The Slight Risk area across the Plains was expanded eastward into
eastern Kansas and far northern Oklahoma, which was supported by
hi- res CAM QPF, high HREF probabilities for rain rates exceeding 1
inch per hour and 2 inches per 6 hours, and moderate HREF
probabilities for 24 hour QPF exceeding 5-year ARIs. The latest
guidance depicted a southern shift and reduction in threat of
excessive rainfall for parts of South Dakota and northern Nebraska,
therefore the northern bounds of the Slight Risk was trimmed down
to eastern Nebraska. Within this Slight Risk area, the high end
potential is expected to focus over eastern Nebraska, where this
will likely become more of a long duration event with high rain
rates in individual storms.

Campbell/Dolan


Day 2
Valid 12Z Sun Aug 31 2025 - 12Z Mon Sep 01 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM SOUTHERN NEW
MEXICO INTO WEST/CENTRAL TEXAS AND FOR EASTERN NEBRASKA...

Convection over eastern Nebraska and Kansas will likely see enough
instability and moisture to support high rain rates. Soils in this
region should also be saturated from heavy rain/storms expected on
Saturday, resulting in a heightened flash flood risk. The inherited
Slight Risk was expanded south and east to cover more of eastern Kansas.

The Slight Risk area in Texas was also expanded to include more of
eastern Texas and far southeast Arizona. This was to account for
an increasing trend in QPF and the potential for repeat
thunderstorm activity over areas that will be saturated by storms.
The better focus for higher QPF will be for locations near or east
of the Hill Country across eastern Texas.

The broader Marginal Risk areas for the southern tier and portions
of the Central/Northern Plains continue to highlight the level
threat for excessive rainfall and flooding potential across the region.

Campbell


Day 3
Valid 12Z Mon Sep 01 2025 - 12Z Tue Sep 02 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR THE SOUTHERN
TIER, PLAINS AND TENNESSEE VALLEY...

A surface front will continue to be draped across the southern
tier of the country providing a focus for the monsoonal moisture
and Gulf moisture. There will be some upper level support for
isolated convection therefore the Marginal Risk was maintained from
New Mexico and southeast Arizona across southern/central parts of
Texas and the Gulf Coast through the Florida Peninsula.

To the north, a frontal system and a shortwave or two aloft will
support storms with higher rain rates across the Mid-Mississippi
Valley and the Tennessee Valley to Southern Appalachians.
Maintained the Marginal Risk areas for the Tennessee Valley and for
the Plains.

Campbell
$$
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FOUS30 KWBC 310805
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
405 AM EDT Sun Aug 31 2025

Day 1
Valid 12Z Sun Aug 31 2025 - 12Z Mon Sep 01 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM SOUTHERN NEW
MEXICO INTO WEST/CENTRAL TEXAS AND FOR EASTERN NEBRASKA...

Abundant instability and moisture influx will help maintain
convection over the Plains. High rain rates combined with nearly
saturated soils from recent heavy rain/storms will keep an elevated
threat for flash flooding for the region. A Slight Risk clips far
southeast South Dakota, eastern Nebraska, eastern Kansas, northwest
Missouri and western Iowa.

Easterly flow will allow storms that develop over the Gulf to move
into the coastal areas of Texas and western Louisiana. Meanwhile
the stalled frontal boundary over the area will continue to provide
forcing into the rest of Texas and New Mexico. For many areas, dry
clay soils will allow for most of the rainfall in the typically
dry desert areas to convert to runoff quickly. The better focus
for higher QPF will be for locations near or east of the Hill
Country across eastern Texas. A Slight Risk spans from southeast
Arizona to the southeast coast of Texas within a broader Marginal
Risk for the southern tier and portions of the Central/Northern Plains.

Campbell


Day 2
Valid 12Z Mon Sep 01 2025 - 12Z Tue Sep 02 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR THE
SOUTHERN TIER, PLAINS AND TENNESSEE VALLEY...

A frontal system and a shortwave or two aloft will support storms
with higher rain rates across the Lower Missouri/Mid-Mississippi
Valley and the Tennessee Valley to Southern Appalachians. The
Marginal Risk areas for the Tennessee Valley and for the Plains
remain in effect for this period.

The stalled frontal boundary along the Gulf Coast and into Texas is
expected to advance a little southward during this period leading
to the QPF footprint being offset from prior days which will limit
the flooding potential. The heaviest rain is still expected to
focus along the I-10 corridor from Houston to San Antonio and may
still cause impacts. A broad Marginal Risk remains in effect from
the Southwest, southern Texas/western Gulf coastline an much of the
Florida peninsula.

Campbell


Day 3
Valid 12Z Tue Sep 02 2025 - 12Z Wed Sep 03 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHWEST/CALIFORNIA, FLORIDA, LOWER MISSISSIPPI/TENNESSEE
VALLEYS AND THE UPPER MIDWEST...

A Marginal Risk area was maintained for the Mid-South as shortwave
energy and a weak low traversing the cold front may trigger
convection capable of higher rainfall rates over the region.
Meandering frontal boundaries within an unstable environment will
support heavy rainfall and localized flash flooding potential for
Florida, therefore the Marginal Risk area was kept for this period.

A cold front will drop into the Northern Plains and Upper Midwest
ahead of the strong reinforcing upper trough. Convection is
expected fire up along and ahead of the frontal boundary, with
potential for heavy rainfall. A Marginal Risk area is in effect for
the eastern Dakotas, northern Iowa, Minnesota, northern Wisconsin,
and portions of the UP of Michigan.

Meanwhile, monsoonal moisture is forecast to flow into the
southwestern U.S. underneath the mean upper ridge for scattered
showers and thunderstorms. A Marginal Risk span from southern
Colorado/New Mexico westward to eastern California.

Campbell
$$
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FOUS30 KWBC 010753
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
353 AM EDT Mon Sep 1 2025

Day 1
Valid 12Z Mon Sep 01 2025 - 12Z Tue Sep 02 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHERN TIER, PLAINS, EAST COAST OF FLORIDA, AND TENNESSEE
VALLEY...

The stalled frontal system and monsoonal moisture will persist
across southern Arizona, New Mexico, and Texas. Isolated convection
across the region expected, keeping the threat for flash to
isolated instances. A Marginal Risk remains in effect for portions
of Arizona, New Mexico, and western/southern Texas.

Easterly onshore flow into Florida warrants maintaining a Marginal
Risk for the eastern coastal areas.

Antecedent dry conditions along the Appalachians should preclude
any flash flooding. Better coverage of convection should stay
further west into central Tennessee and northern Alabama. A vort
max tracking east across Tennessee will be the forcing mechanism
for any convection across Middle Tennessee. A Marginal Risk was the
appropriate threat level for this period.

Finally, the Marginal in the Plains was reshaped to a slightly more
SW-NE orientation rather than mostly N-S. Instability and abundant
cloud cover should limit the flooding threat, but prior rains from
previous days in the form of more saturated soils could support an
isolated flash flooding risk.

Campbell/Wegman


Day 2
Valid 12Z Tue Sep 02 2025 - 12Z Wed Sep 03 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE MIDDLE TENNESSEE VALLEY...

Remnant convection from the overnight period on Monday night will
persist into Tuesday as a reinforcing shortwave digs southward and
reaches Middle Tennessee by Tuesday night. A weak, but still
significant low level jet will advect Gulf moisture northeastward
across the Deep South and into Tennessee on Tuesday, which will
keep a steady supply of fuel in place for any convection. Thus,
expect a long-duration rain event, that while much of it will be
light, the LLJ advecting moisture into Tennessee and various
different sources of forcing will support some storms becoming
strong and able to produce heavy rain. The storms will also be
slow-moving, which will lengthen the amount of time any area sees
heavy rain. A Slight remains in effect for portions of Mississippi,
Alabama, and Tennessee.

A cold front will drop into the Northern Plains and Upper Midwest
ahead of the strong reinforcing upper trough. Convection is
expected fire up along and ahead of the frontal boundary, with
potential for heavy rainfall. A Marginal Risk area is in effect for
the eastern Dakotas, northern Iowa, Minnesota, northern Wisconsin,
and portions of the UP of Michigan.

The stalled out front across Florida will support more widespread
convection Tuesday afternoon across much of the Peninsula, while
the Panhandle dries out a bit from prior days' rains. A second
shortwave and associated front will produce areas of heavy rain
across portions of the upper Midwest. A Marginal Risk remains in
effect for most of central and southern portions of the Peninsula.

Monsoonal moisture is forecast to flow into the southwestern U.S.
underneath the mean upper ridge notably shifted a bit westward for
this period. Scattered convection expected across the region and
is covered by a Marginal Risk spanning from eastern California,
Arizona, New Mexico and into southern Colorado.

Campbell/Wegman


Day 3
Valid 12Z Wed Sep 03 2025 - 12Z Thu Sep 04 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PARTS OF THE
SOUTHWEST, FLORIDA, AND THE UPPER GREAT LAKES/UPPER MIDWEST...

Deep moisture along the stalled frontal boundary will continue to
generate convection capable of producing heavy rain across the
Florida Peninsula. A Marginal Risk is in effect for most of
central and southern portions of the state. Meanwhile, monsoonal
moisture and diurnal heating will continue to trigger convection
across the West/Southwest maintaining an elevated threat for
isolated flash flooding for vulnerable locations. A Marginal Risk
is in effect from New Mexico to eastern California. Further north,
heavy rainfall is expected across portions of the Upper
Midwest/Upper Great Lakes as the frontal boundary continues to
advance eastward. A Marginal Risk encompasses portions of Wisconsin
and northern Michigan.


Campbell
$$
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FOUS30 KWBC 020818
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
418 AM EDT Tue Sep 2 2025

Day 1
Valid 12Z Tue Sep 02 2025 - 12Z Wed Sep 03 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHERN CALIFORNIA AND SOUTHERN ARIZONA...

...Southwest...

There will be a nearly continuous anomalous surge in monsoonal
moisture into the Sierra Nevada due to the position of the upper
ridge axis to the east and a weak upper low along the central
California coast to the west. PW anomalies of 2 to 3 sigma are
forecast from the lower Colorado River up trough the Sierra Nevada
and even into southern Oregon by 00Z Wed. Impressive CAPE will also
be present across southern Arizona and southern California, showing
support for heavy rainfall especially over flashy prone areas.
This environment has the potential for more than just isolated
areas of flash flooding, therefore a Slight Risks were raised for
southern Arizona and southern California.

...Mid-South through Tennessee Valley...

Remnant boundaries from ongoing convection today combined with
additional lift from a digging trough from the central U.S. should
allow convective activity to be in similar areas (and west) from
yesterday's coverage. However, moisture is limited to around 1.5".
This uptick will allow for some greater rates and motion should
remain slow overall, but overall the rainfall magnitude continues a
decreasing trend. A Marginal Risk remains in effect from central
Mississippi to Kentucky.

...Upper Midwest...

During this period a cold front is expected to traverse across the
Dakotas and encounter pooled moisture with a PW of 1.25", which is
1 sigma above normal. Diurnally enhanced convection is expected
fire up along and ahead of the frontal boundary and will have the
potential to produce heavy rainfall for Minnesota, northern Iowa,
Wisconsin and the U.P. of Michigan. A Marginal Risk was kept for this area.

Campbell/Jackson


Day 2
Valid 12Z Wed Sep 03 2025 - 12Z Thu Sep 04 2025

...THERE IS A SLIGHT RISK FOR PORTIONS OF SOUTHERN CALIFORNIA AND
SOUTHER ARIZONA...

...Southwest...

Anomalous monsoonal moisture will continue to affect northward
from the lower Colorado Valley through the Sierra Nevada and much
of Nevada. Diurnally- driven activity can be expected again over
the Sierra Nevada which may be locally excessive, as well as much
of Nevada through western Arizona and southwest Utah. A broad
Marginal Risk cover much of Arizona,southeast Utah, southern
Nevada, and eastern/southern California. The presence of strong
CAPE embedded with the deep column of moisture, especially across
southern Arizona and across the Transverse and Peninsular Ranges of
southern California will be conducive for heavy rainfall and
scattered areas of flash flooding. These locals will be vulnerable
to the high rainfall rates, especially in the flashy prone
locations. A Slight Risk was raised in coordination with the local
forecast offices.

...Central U.S...

Elevated moisture ahead of the strong cold front sweeping down the
Plains will trigger heavy rainfall again. Enough focus is present
to warrant maintenance of the Marginal Risk around the central
Great Lakes though timing is in question. While much of the
activity should be progressive, there is a repeating threat on the
southern end of activity along the southern Kansas/Missouri
border- a Marginal Risk was carried on for this period.

...Florida...

Enhanced rainfall expected to develop within the very moist airmass
along the stalled frontal boundary. Individuals cells will focus
heavy rainfall over the southern peninsula and the Keys thus
keeping an elevated threat for flash flooding.

Campbell


Day 3
Valid 12Z Thu Sep 04 2025 - 12Z Fri Sep 05 2025

...THERE IS A MARGINAL RISK AREA FOR PORTIONS OF FLORIDA,
SOUTHWEST/GREAT BASIN, AND THE NORTHEAST...

...Florida...

The environment will remain nearly the same as the Day 2 period,
thus convection will persist. Heavy rain will be possible therefore
the Marginal Risk was maintained southern Florida and expanded
southward to cover the Keys.

...Northeast...

The cold front passing through the Lower Great Lakes and into the
Northeast will be fairly progressive, however there are signals
for higher QPF to focus across central and northern portions of New
York. Parts of the region have been drier with some areas with
notable drought conditions, which will limit the potential for
impacts from heavy rainfall. The highest amounts are expected for
the more elevated locations which will increase the threat for
flooding concerns. A Marginal Risk area was maintained from the
previous Day 4 but with portions of western and eastern new York
trimmed out given the D0/D1 drought conditions.

...Southwest, California and southern Great Basin...

The monsoonal moisture will continue to advect into the
southwestern U.S. underneath the mean upper ridge, promoting
scattered showers and thunderstorms. Moisture anomalies are
expected to be the greatest for portions of California and Nevada.
A broad Marginal Risk encompasses eastern California, most of
Nevada, southeast Utah, Arizona and west/central New Mexico.

Campbell
$$
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FOUS30 KWBC 030850
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
450 AM EDT Wed Sep 3 2025

Day 1
Valid 12Z Wed Sep 03 2025 - 12Z Thu Sep 04 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHERN ARIZONA...

...Southwest...
A broad area of instability and above normal moisture will bring a
localized flash flood risk to much of the southwestern U.S. today.
HREF guidance indicates the best convective coverage will be
across southern AZ where neighborhood probabilities of 2"+ amounts
are 30-50%. This generally looks to be where the better
instability is forecast today, and also where the heaviest rainfall
occurred yesterday. Thus maintaining the Slight risk across this
areas seems reasonable.

...South FL...
A wet pattern will persist over south FL through Friday with
localized flash flooding possible each day. The overall pattern
does not change too much, with a stationary front in the low
levels, an upper jet to the north providing some right entrance
region ascent, and broad mid level troughing. It seems likely that
rounds of convection will occur each day, and with PWs around 2.3",
heavy rainfall rates are likely. There is some uncertainty with
the axis of heaviest rainfall each day, with some models favoring
the Keys, and given the location of the stationary front, this may
make sense. However it still seems likely that heavier convection
will impact the urban corridor of southeast FL at times as well.
Uncertainty regarding both the axis and also the speed of
convection, whether it tends to propagate eastward quickly or can
hang up, dictates keeping the risk at Marginal for now. Although
could certainly see the need for a targeted Slight risk along the
southeast FL urban corridor at some point over the next 3 days
given the potential for multiple rounds of heavy rainfall.

Chenard

Day 2
Valid 12Z Thu Sep 04 2025 - 12Z Fri Sep 05 2025

...THERE IS A SLIGHT RISK FOR PORTIONS OF SOUTHEAST CALIFORNIA AND
CENTRAL AND SOUTHERN ARIZONA...

...Southwest...
Thursday is looking like a more active day across portions of AZ
into southeast CA as the area begins to feel the impacts of a
stronger moisture surge ahead of Lorena. An uptick in moisture and
low level flow should help drive a more organized convective
threat. Rather impressive instability for this part of the country
is forecast, with values upwards of 2000-3000 J/KG, and this
combination of above average PWs and instability should support
intense rainfall rates. Always worry about cloud cover impacting
instability, which could happen in spots, but the overall model
signal certainly favors areas of robust instability. In a part of
the country where model QPF struggles, CAPE and PW overlap often
ends up being a better flash flood potential indicator. Given the
ingredients in place, we went ahead and upgraded to a Slight risk
for much of central and southern AZ into southeast CA. Additional
expansion into more of southeast CA are possible going forward.

...South FL...
A wet pattern will persist over south FL through Friday with
localized flash flooding possible each day. The overall pattern
does not change too much, with a stationary front in the low
levels, an upper jet to the north providing some right entrance
region ascent, and broad mid level troughing. It seems likely that
rounds of convection will occur each day, and with PWs around 2.3",
heavy rainfall rates are likely. There is some uncertainty with
the axis of heaviest rainfall each day, with some models favoring
the Keys, and given the location of the stationary front this may
make sense. However it still seems likely that heavier convection
will impact the urban corridor of southeast FL at times as well.
Uncertainty regarding both the axis and also the speed of
convection, whether it tends to propagate eastward quickly or can
hang up, dictates keeping the risk at Marginal for now. Although
could certainly see the need for a targeted Slight risk along the
southeast FL urban corridor at some point over the next 3 days
given the potential for multiple rounds of heavy rainfall.

Chenard

Day 3
Valid 12Z Fri Sep 05 2025 - 12Z Sat Sep 06 2025

...THERE IS A MARGINAL RISK AREA FOR PORTIONS OF FLORIDA,
AND THE WESTERN U.S....

...Southwest...
More uncertainty with the flash flood forecast on Friday compared
to Thursday. The potential is there for more direct impacts from
Lorena across portions of AZ and NM, but confidence on the details
is low. The GFS, RRFS and GFS based hurricane model (HAFS) have
consistently been indicating a stronger system that is able to move
into northwest Mexico. This evolution would likely result in
strong enough low level forcing to drive convection and a flash
flood risk over portions of southeast AZ into southwest NM. However
the non-NCEP global models and the NAM suggest the low level
center of the system weakens and stays offshore Baja California,
with just the mid and upper level energy ejecting northeastward.
This would probably result in quite a bit of mid and upper level
moisture moving into AZ and NM, and while this could result in a
steady rainfall, the cloud cover would probably hinder
destabilization and keep rainfall rates and the flash flood risk
lower. So this could be a case where the areal averaged rainfall is
higher, but the flash flood risk is actually lower given the
decreased rates. Given this uncertainty we opted to stick with a
Marginal risk in the ERO despite our deterministic QPF showing
upwards of 1-2" of rain over southeast AZ into southwest NM. We
will continue to monitor trends and adjust as needed on future
updates.

Elsewhere across the West the large Marginal risk area stretches
northward into OR and as far east as CO. The overall synoptic
pattern favors isolated to scattered convection over this entire
area, and the forecast PWs and instability would support locally
heavy rainfall rates. At the moment not seeing enough coverage to
justify any Slight risk areas, but we will continue to monitor.
Sometimes we can get a more organized flash flood risk develop on
the edge of the deeper tropical moisture, where cloud cover is low
enough to allow for destabilization, but moisture is still high
enough for heavy rates.

...South FL...
A wet pattern will persist over south FL through Friday with
localized flash flooding possible each day. The overall pattern
does not change too much, with a stationary front in the low
levels, an upper jet to the north providing some right entrance
region ascent, and broad mid level troughing. It seems likely that
rounds of convection will occur each day, and with PWs around 2.3",
heavy rainfall rates are likely. There is some uncertainty with
the axis of heaviest rainfall each day, with some models favoring
the Keys, and given the location of the stationary front this may
make sense. However it still seems likely that heavier convection
will impact the urban corridor of southeast FL at times as well.
Uncertainty regarding both the axis and also the speed of
convection, whether it tends to propagate eastward quickly or can
hang up, dictates keeping the risk at Marginal for now. Although
could certainly see the need for a targeted Slight risk along the
southeast FL urban corridor at some point over the next 3 days
given the potential for multiple rounds of heavy rainfall.

The large scale pattern becomes more meridional by Friday, with
upper level flow becoming more southerly over south FL and the
upper jet orientation favoring a bit more upper level divergence.
Thus could potentially see a pattern that may favor more of a
stationary or training convective threat along the urban corridor
of southeast FL. However the location of the front by then will
play a role in this, and so not confident enough to go with a
Slight risk at this point.

Chenard
$$
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FOUS30 KWBC 040849
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
449 AM EDT Thu Sep 4 2025

Day 1
Valid 12Z Thu Sep 04 2025 - 12Z Fri Sep 05 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEAST CALIFORNIA AND CENTRAL AND SOUTHERN ARIZONA...

...Southwest...

The signal is clear within all CAMs leading to a strong
probability assessment for 3 and 6hr FFG exceedance intervals, each
carrying 50+% over a large area extending from Tuscon all the way
to the Colorado River basin between the 18-06z time frame in the
period. Rates of 1-2"/hr will be plausible in this setup as PWATs
remain ~2 deviations above normal, a signal favoring locally heavy
rainfall and heightened flash flood concerns over flashy
soil/terrain features. Rather impressive instability for this part
of the country is forecast, with values upwards of 2000-3000 J/KG,
and this combination of above average PWs and instability should
support intense rainfall rates. Always worry about cloud cover
impacting instability, which could happen in spots, but the overall
model signal certainly favors areas of robust instability. In a
part of the country where model QPF struggles, CAPE and PW overlap
often ends up being a better flash flood potential indicator. A
Slight risk for much of central and southern Arizona into southeast
California was maintained for this period.

...South Florida...

A persistent wet pattern to continue through the weekend thanks to
stationary front in the low levels, an upper jet to the north
providing some right entrance region ascent, and broad mid level
troughing. Rounds of convection will occur each day, and with PWs
around 2.3", heavy rainfall rates are likely. The exact location
of the axis of heaviest rainfall is a bit uncertain, but most of
the guidance is favoring the Keys and southern portions of the
peninsula. Heavier convection may impact the urban corridor of
southeast Florida at times as well. A Marginal Risk area remains in
effect for southern Florida and the Keys.

...Kentucky...

Isolated flash flooding possible across eastern Kentucky and points
eastward this morning. Individual storms will be capable of
producing 1-2 inches/hour, particularly over a part of the country
that is vulnerable to these intensities. Please refer to Mesoscale Precipitation Discussion #1045 for additional details.

Campbell/Chenard/Kleebauer


Day 2
Valid 12Z Fri Sep 05 2025 - 12Z Sat Sep 06 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR SOUTHEAST
ARIZONA AND SOUTHWEST NEW MEXICO....

...Southwest...

The exact track of the circulation from Lorena as it approaches
Sonora from the California Baja remains a bit uncertain within the
latest guidance. Some of the model guidance remains particularly
aggressive with holding the center of circulation to the
International border, just south of southeastern Arizona leading to
multiple solutions (GFS/RRFS/NAM/HAFS suite/HWRF) indicating a
swath of heavy rainfall impacting at least portions of southeast
Arizona into southwest New Mexico. ECMWF/CMC and mean ensemble
output remains not as aggressive as the previous models referenced
putting a little more emphasis on the low degrading prior to
reaching northern Sonora leading to the remnant moisture field not
advecting further north.

Assessment of the guidance compared to reality is important in
this scenario as major discrepancies early on would very well
inhibit model outputs through the course of the run. As of now, the
cluster with the greater outputs over Arizona/New Mexico are
handling the system a bit better which trends more in favor of the
wetter solutions as we move forward in time. Ensemble bias
corrected QPF was also particularly wet aiding to a little better
consensus on what could transpire across the high deserts near the
border. Ensemble totals between 1.5-3" with locally higher are
being forecast in those more substantial outputs, a range that
would cause some flash flood concerns, especially when you add in
the more effective warm rain processes being depicted when looking
at forecast soundings over parts of the aforementioned area. PWAT
anomalies closer to 3 deviations above normal would be common in
the current expected evolution, plentiful for more locally
significant impacts.

The large Marginal risk area spans from Oregon and as far east as
Colorado and New Mexico. The overall synoptic pattern favors
isolated to scattered convection over this entire area, and the
forecast PWs and instability would support locally heavy rainfall rates.

...South Florida...

The overall pattern described during the Day 1 period is not
expected to change much and locally heavy rain between 2-4" are
forecast in the period, however its location will certainly be
important with the urban centers the most favorable for at least
scattered flash flood prospects. The large scale pattern becomes
more meridional by Friday, with upper level flow becoming more
southerly over south Florida and the upper jet orientation favoring
a bit more upper level divergence. Thus could potentially see a
pattern that may favor more of a stationary or training convective
threat along the urban corridor of southeast Florida. A Marginal
Risk remains in effect for southern Florida and the Keys.

Campbell/Kleebauer/Chenard


Day 3
Valid 12Z Sat Sep 06 2025 - 12Z Sun Sep 07 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM TEXAS TO
THE PACIFIC NORTHWEST, SOUTHERN FLORIDA AND NEW ENGLAND...

...West, Southwest and Southern Plains...

During this period a frontal boundary will stretch from the Gulf
westward into Texas. Some enhanced moisture left over from Lorena
and instability will be present over the Southern Plains, which
could allow for locally heavy rainfall to occur. A broad Marginal
is in effect for the western half of Texas into the southern High
Plains, Colorado, Southwest, Great Basin, Idaho and Oregon.

...Florida and New England...

The frontal system over Florida and northeast in the western
Atlantic will provide a focus for moisture to pool, leading to at
least scattered diurnal convection each day. Excessive rainfall
across Florida will likely focus across the southeast peninsula in
Miami-Dade County and vicinity. The Marginal Risk up north covers
most of Vermont, New Hampshire and Maine.

Campbell
$$
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FOUS30 KWBC 050808
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
408 AM EDT Fri Sep 5 2025

Day 1
Valid 12Z Fri Sep 05 2025 - 12Z Sat Sep 06 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
SOUTHWEST, PORTIONS OF THE TENNESSEE VALLEY, AND FOR SOUTH FLORIDA...

...Southwest...

Monsoonal moisture combined with some of the remnant moisture from
Lorena will impact much of the Southwest today. However, with
Lorena's low-level circulation now expected to dissipate offshore
and not move northeastward into northern Mexico, the share of that
moisture making it into the Southwest has been steadily decreasing.
The result is less coverage of showers and storms in favor of a
more showery weather regime. In coordination with TWC/Tucson, AZ
and EPZ/El Paso, TX forecast offices, the inherited Slight Risk for
portions of Arizona and New Mexico was removed with this update.

...Tennessee Valley...

Training thunderstorms, some of them severe, on the tail end of a
wound-up occluded front, will track northeastward along the western
side of the Appalachians this afternoon and evening. While the
storms are likely to be fast-moving, the influx of moisture
parallel to the cold front approaching from the northwest will
favor a period this afternoon where storms could redevelop and
train along the same areas in the form of multiple clusters of
storms. Thus, a new Marginal Risk was introduced covering Middle
Tennessee and into eastern Kentucky. The greatest threat of flash
flooding looks to be in the urban areas in and around Nashville.

...South Florida...

A stalled out tropical wave at the tail end of a front well off the
Eastern Seaboard will continue to plague much of the Florida
Peninsula with showers and slow-moving and erratic thunderstorms
this afternoon into this evening. While the bulk of the expected
rainfall is expected to target south Florida and the Keys, some of
that rainfall activity may sneak a bit further north into central
Florida. The greatest threat for flash flooding will be into the
highly urbanized I-95 corridor from Palm Beach through Miami this
afternoon and this evening. Given inherent uncertainty with where
the storms will set up and how they will be moving, a Marginal Risk
remains in place, though local areas where storms are the most
persistent could quite possibly have higher-level impacts.

Wegman


Day 2
Valid 12Z Sat Sep 06 2025 - 12Z Sun Sep 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE INTERMOUNTAIN WEST, FLORIDA, AND THE NORTHEAST...

...Intermountain West...

Monsoonal moisture will continue to steam northward across portions
of the West on Saturday. While some of that moisture can be
directly attributed to the remnants of Lorena, Lorena will have
long since ceased existing as a tropical entity by this period on
Saturday. Thus, the forcing mechanisms for heavy rain will turn to
more typical monsoonal factors, such as upsloping and an impinging
shortwave trough. For some areas, this will result in a higher
threat for heavy rain and subsequent flooding, particularly into
far southern Arizona and much of New Mexico. Nevertheless, no one
forcing will be strong enough to promote organization and more
robust heavy rains, so the Marginal Risk for the area remains in
place. Further north, a digging shortwave trough will be the
primary focus driving the heavy rain, as the storms tap into some
of that monsoonal moisture.

...Northeast...

The cold front that was moving into the Appalachians on Friday will
continue across the urban corridor of the Northeast on Saturday.
Diurnal heating and robust moisture transport up the I-95 corridor
will support training storms, which may be locally enhanced with
upslope flow from the DC Metro area northeast through Boston and
into Maine. Corfidi Vectors parallel to the frontal interface
suggest fast-moving training thunderstorms will be common. The
widespread urbanization along I-95 also supports at least a
Marginal/isolated flash flooding risk. It will be far from a rainy
day for most, with most areas staying dry. However, when storms
move through, they will likely be strong, with abundant moisture to
tap into. Thus, the inherited Marginal Risk was expanded well south
and west to include all of the I-95 corridor through the DC Metro
area. Localized urban flooding will remain the primary threat from
any repeating storms despite very dry antecedent conditions. The
front will continue eastward into Saturday night, ushering in yet
another cool and very comfortable air mass from Sunday through much
of next week. The rainfall forecast has most notably increased
across portions of New England, from NYC north. This is where the
greatest risk of flash flooding will be on Saturday.

...Florida...

The stalled out front and associated tropical wave will slowly
begin to retrograde back towards the north on Saturday, resulting
in a spreading of the potential for heavy rains well up the Florida
Peninsula. Thus, the Marginal Risk was expanded north through
central Florida with this update. High uncertainty as to
convective coverage and behavior will keep a Marginal going for the
time being, but there remains some potential a later Slight may be
needed in portions of Florida.

Wegman


Day 3
Valid 12Z Sun Sep 07 2025 - 12Z Mon Sep 08 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHERN PLAINS AND THE FLORIDA PENINSULA...

...Southern Plains...

While some monsoonal moisture will linger in portions of the West
into Sunday, there will be far more of a Gulf component to the
moisture as predominant southeasterly flow advects deep Gulf
moisture into south Texas, which will combine with what moisture is
left from the monsoon. While the moisture will be plentiful, the
forcing will be anything but, as a strong upper level ridge builds
across the area. The result will be storms that for many areas will
be tied to the mountains, cold pools from other storms, or
localized pockets of higher instability. Thus, storm organization
across Texas on Sunday will be quite lacking. Given this, despite
the atmospheric moisture, soils across south Texas are quite dry,
which is average for this time of year. Thus, for most areas, rain
from any storms will be largely beneficial and will soak into the
ground, precluding much flooding threat. Thus, in coordination with
EWX/San Antonio, TX, CRP/Corpus Christi, TX, and SJT/San Angelo, TX
forecast offices, the inherited Slight for portions of the Hill
Country was removed with this update.

...Florida Peninsula...

It's the same old song and dance weather-wise across Florida once
again on Sunday. The front that has been stuck there will still be
there, taking advantage of plentiful Gulf/Atlantic moisture.
Uncertainty with how the storms will form and organize remains
high, so the Marginal Risk remains in place, with a northward
expansion included to account for potentially heavy rains across
central Florida from the day Saturday continuing into Sunday.

Wegman
$$
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FOUS30 KWBC 060953
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
553 AM EDT Sat Sep 6 2025

Day 1
Valid 12Z Sat Sep 06 2025 - 12Z Sun Sep 07 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PHILADELPHIA
THROUGH THE NEW YORK CITY METRO...

...Northeast...

The combination of several ingredients all at the same time in an
urban corridor has increased the potential for flash flooding. A
healthy LLJ will advect abundant Gulf/Atlantic moisture north, up
the Eastern Seaboard on Saturday. Expect PWATs to exceed 1.75
inches from Florida into New England as a result of the 25-35 kt
850 mb LLJ moving that moisture northward. Meanwhile, a strong but
rather slow-moving cold front is approaching the Northeast from the
Great Lakes. This cold front will act as a catalyst/forcing
mechanism for numerous showers and thunderstorms to develop this
afternoon in the warm, muggy air mass. Meanwhile, in the upper
levels, a 130 kt SSW to NNE oriented jet will be in place from
western Pennsylvania north to near the southern tip of Greenland.
This puts the urban corridor in the favorable right entrance region
of that jet streak, which will support lift and additional
thunderstorm development. Finally, the storms and strongest forcing
will be moving through the area at peak heating in the mid-
afternoon. This will allow the storms to be at their strongest with
the maximum amount of heating having occurred prior the convective
initiation. A subtle upper level shortwave will also move through
the jet and enter the jet streak this afternoon. This shortwave
will support additional convective development to occur behind the
initial line of storms. This additional convective development
expected is depicted in several of the CAMs model runs, most
notably the 00Z HRRR. While never a perfect prog, the HRRR's
solution if even close to correct will result in multiple inches of
rain from Philly north through NYC. Similar solutions are depicted
in the ARW2, RRFS, and NAMnest.

Expect an initial line of storms to move across northern New Jersey
and into the NYC Metro during the mid to late afternoon, between
3-6pm, with additional lines of progressively weaker convection
moving across the region well into the evening. While most areas
have been very dry of late, with the initial stages of drought
setting in, the consensus of most of this overlapping/training
convection is for it to follow I-95 from Philly up into the NYC
metro, where heavy urbanization has locally lowered FFGs. Thus,
despite empty streams and creeks, multiple rounds of heavy rain in
either continuous or rapidly repeating fashion is still likely to
cause widely scattered instances of flash flooding where the storms
are most persistent over urban areas. In coordination with
OKX/Upton, NY and PHI/Mount Holly, NJ forecast offices, a Slight
Risk upgrade was introduced with this update.

Further north into New England, the forcing is not as likely to
align as areas further south, and therefore only one or two lines
of storms are expected in this area, which has also been very dry
in recent weeks. This should limit flash flooding to isolated
instances. Further south into the DMV, once again expect a line of
storms to move through during the afternoon, but with the forcing
further north, little if any backbuilding or additional convective
development is expected behind the initial line of storms.
Nevertheless with an abundance of moisture available for the storms
to tap as they rumble across the Mid-Atlantic, as well as other
urban concerns, the Marginal Risk remains in place through much of Virginia.

...Tennessee Valley...

The same cold front moving across the Mid-Atlantic and Northeast
will also slowly push south across the Tennessee Valley today.
Being closer to the primary moisture source (the Gulf), storms in
this area will have even more moisture to feed from. However, the
front pushing south will strongly limit any potential for training
or backbuilding. Thus, for most areas, just one round of storms is
all that can be expected. Cell mergers and pre-linear convective
development could allow for isolated instances of flash flooding,
so a Marginal Risk was expanded from the Mid-Alantic down through
Tennessee and northern portions of the Southeast.

...Florida...

A stalled out front draped across the state, as well as an
abundance of deep tropical moisture in place will support yet
another round of afternoon and evening thunderstorms across much of
the Peninsula today into tonight. Since the front, while present,
will be quite diffuse, the guidance is in poor agreement as to
where any storms may organize over Florida, so a larger Marginal
Risk is all there is the confidence for, especially considering the
larger amounts of rain needed to get flash flooding in much of
Florida. The inherited Marginal Risk is largely unchanged.

...West...

Very few changes were needed out west for expected continued
monsoonal convection across much of the Southwest/Four Corners
region. The Marginal risk area was expanded a bit down the Rio
Grande in west-central Texas, but otherwise the area remains
largely the same with few changes. As is typical with the monsoon,
there will likely be feast or famine with many of the storms across
the Southwest today. Most areas will be dry or only see some light
rain, but where the storms are able to organize and concentrate,
some areas may see multiple inches of rain. Given the area's
proclivity to flash flood, the Marginal remains in place for most
of the West.

Wegman


Day 2
Valid 12Z Sun Sep 07 2025 - 12Z Mon Sep 08 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE SOUTHERN
HALVES OF TEXAS AND FLORIDA...

...Texas...

Gulf moisture in place across Texas will interact with some of the
remnant moisture from former Hurricane Lorena on Sunday. PWATs
rising to between 1.75 and 2 inches will be enough moisture to
support widely scattered convection across much of the southern
half of the state. There's considerable disagreement on the
guidance as to where the most convection will organize. Since the
overall forecast is little changed from the inherited forecast, the
Marginal Risk remains largely in lace with few changes.

...Florida...

The stalled out front that remains across Florida will extend
northeastward off the coast of the Carolinas on Sunday. Thus,
expect yet another round of afternoon and evening convection over
much of the Florida Peninsula. There remains some indication that
the convection will favor the eastern side of the state, but since
the area remains in a pattern where much of the Peninsula sees
numerous showers and thunderstorms developing each afternoon, but
with little in the way of organization to them, the inherited
Marginal remains roughly the same, depicting all of the southern
half of the state in an isolated risk for flash flooding. This is
most likely should any storms develop and sit over urban areas, or
in an area that has seen particularly heavy rain in recent days.

Wegman


Day 3
Valid 12Z Mon Sep 08 2025 - 12Z Tue Sep 09 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
FLORIDA PENINSULA AND THE GEORGIA COAST...

...Southeast...

As on previous days, much of the Florida Peninsula will remain
under the influence of a stalled out front that has been sitting
over the state for much of the past week. This will result in yet
another afternoon of numerous convection, which will take advantage
of abundant tropical moisture in the area to support additional
convective development from prior storms' cold pools. Meanwhile,
the front as a whole will very slowly drift northwestward with
time, which will spread the rain chances along the beaches from
Georgia through the Carolinas. There's high uncertainty as to
whether most of the rainfall will even make it to the coast.
Outside of Florida, the coastal areas most likely to see heavy rain
will be the Georgia coastal communities. Otherwise, as in previous
days, there will be little to support organized convective growth
across Florida, so the storms behave erratically in the guidance,
with no particularly strong signals for heavy rain anywhere in
Florida. Therefore, once again, the Marginal Risk remains in place.

Elsewhere, there are a few signals for potential heavy rain into
portions of the upper Midwest, as well as coastal Oregon. In both
areas, the signals are diffuse enough as to preclude any Marginal
Risk issuance for this update. They will continue to be watched, as
any increase in the signal for heavy rain may require a Marginal
Risk issuance.

Wegman
$$
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FOUS30 KWBC 070712
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
312 AM EDT Sun Sep 7 2025

Day 1
Valid 12Z Sun Sep 07 2025 - 12Z Mon Sep 08 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHERN TEXAS AS WELL AS FOR THE SOUTHEAST COAST AND MUCH OF FLORIDA...

...Southern Texas...

The combination of weak "ridge riding" upper level disturbances, a
strong cold front approaching from the northeast, and abundant Gulf
moisture will all poorly come together across portions of southern
Texas from now through the day today and into tonight. Storms
circulating around a well-defined upper level high over
northeastern Mexico are being driven in part due to upsloping in
the easterly flow off the Gulf. Due to the aforementioned poor
merging of these various ingredients and forcings, expect widely
scattered to scattered convection for the rest of the predawn hours
and into much of the day today. However, these storms will really
struggle to organize to result in any more than an isolated flash
flooding threat. High FFGs, about as high as they get, are
plentiful over much of southern Texas, while soil moisture levels
are about average, which works against flash flooding. Thus, any
isolated flooding in southern Texas today will require slow moving
storms hitting just the right area, likely an urban one, to cause
any impacts today.

...Southeast Coast and Much of Florida...

An area of abundant tropical moisture with embedded weak
troughs/waves will remain around the Florida Peninsula today. The
strongest trough will approach the Gulf Coast side of the state
today from the west. Interactions of this trough, any sea breezes,
and the instability difference in the afternoon between the hotter
Peninsula and the adjacent Gulf and Atlantic will be the primary
forcing mechanisms for any storms. Thus, while storm coverage will
likely once again be widely scattered to scattered. The various
forcings likely competing with each other will work to keep any
storms and clusters of storms from organizing into a more
significant flash flooding threat. Further, despite days of
scattered convection across the Florida Peninsula, soil moisture
levels across much of the state remain below normal, meaning most
of the rain that falls from the afternoon and evening storms will
remain beneficial for most. Thus, the Marginal flash flooding
threat is primarily focused on urban areas today, as any storms
will have plenty of moisture to draw from to locally produce multiple-inch-per-hour rainfall rates.

...New England...

The inherited Marginal Risk across the area was dropped with this
update. All of the rainfall across New England this morning is
stratiform, struggling to produce rates even to a half inch per
hour. This is likely to continue today as the cold front causing
the rain continues to press east towards the coast. While a few
areas of embedded convection from mid-level instability can't be
ruled out, fast motion will also cut into the rainfall amount any
one area picks up today.

Wegman


Day 2
Valid 12Z Mon Sep 08 2025 - 12Z Tue Sep 09 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE CENTRAL PLAINS AS WELL AS FOR THE FLORIDA PENINSULA...

...Central Plains...

An area of convection across the central Plains early Monday
morning will be ongoing at the start of the period. The storms will
develop along a warm frontal interface, where a seasonably cold and
dry air mass will be in place across much of the eastern half of
the country, meanwhile warmth and moisture will be moving north on
an LLJ up the Plains to the west. This will result in a somewhat
unusual scenario where the eastward moving storms will be moving
into a very hostile environment. This will greatly impede the
storms ability to make eastward progress. Thus, the greatest flash
flooding threat, albeit isolated, will be in the area where the
storms form. This is most likely Monday morning across central
Kansas. By mid to late morning, typical diurnal heating will
disrupt the warm frontal interface, with the collapse of the
forcing resulting in the typical weakening of the convective
complex across Kansas. Isolated to widely scattered convection will
continue in fits and spurts over eastern Kansas and adjacent areas
of the neighboring states, but the storms are unlikely to regain as
much organization as they'll have in the early morning hours
Monday. Renewed convection may form further east towards the Kansas
City Metro Monday night, but once again are unlikely to be quite as
organized and have as much coverage as Monday morning's convection
further west.

...Florida Peninsula...

Monday will be a repeat scenario of many afternoons of the past
week or more across Florida. A stationary plume of tropical
moisture will remain firmly entrenched across the state. A nearly
stationary low over the western Gulf will draw additional moisture
and storms towards the west coast, while stationary fronts,
boundaries, and old cold pools will locally provide their own
forcing Monday afternoon. Thus, the result will be the
same...multiple clusters of storms popping up at random across much
of the Florida Peninsula, but just as often as not competing with
each other. Once again, any isolated flash flooding threat will be
where cell mergers or slow moving storms happen to stall out over
urban or other flood prone areas.

Wegman


Day 3
Valid 12Z Tue Sep 09 2025 - 12Z Wed Sep 10 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
SOUTHEASTERN COAST AND THE FLORIDA PENINSULA AS WELL AS FOR
PORTIONS OF NORTHERN IDAHO AND WESTERN MONTANA...

...Southeast...

A trough that has been parked across the Florida Peninsula for well
over a week and associated boundary that has been off the coast of
the Carolinas for the past several days will begin to move
northwest back towards the coast as a warm front on Tuesday. A
mesolow may form along the front which may also help move the heavy
rain associated with the boundary northwestward towards the coast
of the Carolinas. The trough, while it has been in place for an
extended period of time, still will demarcate a strong boundary
between a cool, Fall-like air mass over much of the East Coast, and
a typical summery airmass characterized by hot and very humid
conditions. Thus, the trough will still be plenty able to provide
the forcing for strong thunderstorms capable of heavy rain. As the
heavy rain approaches the coast Tuesday, any flash flooding for
coastal communities will result from that heavy rain,
urbanization, and a coincident high tide. Uncertainty with where
exactly that axis of heaviest rain will set up will preclude any
possible upgrades to the ERO at this time, but too much more of a
westward shift of the heaviest rain into the coast will support
possible upgrades in future updates.

Meanwhile over Florida, the primary forcings will be a slow and
erratic moving low over the western Gulf, and the front/trough
centered off the coast, but moving towards the coast. There is
greater potential for more widespread rains across the Florida
Peninsula on Tuesday due to these two forcings moving in closer
proximity to each other. Regardless, any potential Slight Risk
upgrades will be highly dependent on the rainfall footprint of
prior days' rains.

...Pacific Northwest...

A large cutoff low parked over Washington State and Oregon will
pinwheel several pieces of shortwave energy northward along its
eastern periphery across Idaho and Montana on Tuesday. Abundant
forcing and upslope support will use what moisture is available to
result in scattered convection across the region Tuesday afternoon
during peak heating. Since the cutoff low will be barely moving,
this will allow for an extended period where the region will be in
the most favorable region for widespread lift. Thus, while the
heaviest rainfall rates and most widespread convective converage
will be in the afternoon and evening during peak heating, showers
and storms will continue both before and after this time period,
contributing to an isolated flash flooding threat. Should forecast
moisture availability increase during this time with future
updates, there is some potential a targeted Slight Risk area may be needed.

Wegman
$$
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FOUS30 KWBC 080858
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
458 AM EDT Mon Sep 8 2025

Day 1
Valid 12Z Mon Sep 08 2025 - 12Z Tue Sep 09 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTION OF
OREGON, NORTHERN CALIFORNIA, THE SOUTHERN AND CENTRAL PLAINS, THE
UPPER MISSISSIPPI RIVER VALLEY, AND FLORIDA PENINSULA...

...Texas Panhandle into the Central Plains...
An ongoing convective complex is expected to produce areas of
locally heavy rainfall across central/eastern Kansas toward the
beginning of the forecast period (early Monday morning).
Convergence on the nose of strong low-level flow amid modestly
steep mid-level lapse rates aloft are likely to sustain the storms
for a few hours (between 12-18Z Monday) before veering and
weakening low-level flow causes weakening. Local
backbuilding/training could result in rates exceeding 1 inch/hr
locally, which may result in a few issues with excessive runoff.

Isolated thunderstorm activity is expected from southwestern Kansas
through the Texas Panhandle during the afternoon and evening hours.
The Marginal Risk is being maintained for consistence with prior
forecasts, although newest models depict modest convective
coverage. Nevertheless, supercellular wind profiles and steep lapse
rates aloft may result in intense convection and local rain rates
exceeding FFG for a few hours during the afternoon and early
evening. This Marginal is conditional on sufficient convective
coverage for localized prolonging of heavier rainfall.

Lastly, models depict a resurgence of elevated convection on the
nose of strong low-level flow. The best convergence (and resultant
convective coverage) should extend from southeastern Nebraska south-southeastward along the Kansas/Missouri border region.
Localized backbuilding and training could result in spots of 2-4
inch rainfall totals, and flash flooding is possible on an isolated
basis. Soil moistures are relatively dry though, further suggesting
only an isolated flash flood threat.

...Oregon, northern California...
A substantial mid-level system will approach the region from the
northeastern Pacific during the afternoon and evening.
Ascent/cooling aloft will be well aligned with peak heating,
resulting in sufficient instability for widespread showers and
occasional thunderstorms. Recent CAMs suggest an area of focus for
convection across higher terrain of southwestern Oregon (near the
Medford area) and into terrain-favored areas of northern
California. Appreciable mid-level lapse rates and PW values
approaching 1 inch suggest potential for several areas of wetting
convection, and areas of flash flooding are possible especially
near burn scars and low-lying, flood prone areas. Deeper convection
may also extend toward northern Oregon along the Columbia River
Basin, with isolated flash flood potential expected.

...Upper Mississippi Valley...
Low-level warm advection across a warm frontal zone from the
Dakotas into Iowa should result in areas of showers and
thunderstorms by 00Z. The orientation of this convection favors
some training/backbuilding that could enhance rain rates locally.
2-3 inch totals are expected, with locally higher amounts possible
particularly across northeastern Minnesota.

...Florida...
A nearly stationary front will remain across northern Florida.
Abundant moisture (2+ inch PW values) should reside south of this
front. A weak low should also reside just west of the state over
Gulf of America waters. Convection is expected to develop over much
of the Peninsula in tandem with daytime heating and
destabilization. Cells should remain relatively slow-moving, with
areas of 2+ inch/hr rain rates (and 3 inch totals) expected
throughout the forecast period. Isolated flash flooding is possible
especially where these heavier rates can materialize over
urbanized/sensitive areas.

Cook


Day 2
Valid 12Z Tue Sep 09 2025 - 12Z Wed Sep 10 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
FLORIDA PENINSULA...

Few changes were made from the inherited Marginal Risk area
inherited from yesterday's Day 3 ERO. The quasi-stationary surface
boundary over north Florida early Tuesday will nudge slowly into
central FL by Wednesday morning as southern periphery of the mid-
upper level trough remains parked across the central Gulf Coast
region. Continued large-scale forcing downstream of the upper
trough -- weak upper level difluence and subtle shortwave
energy/periodic DPVA -- will again favor more widespread/organized
convection during the peak heating hours from late morning into
early evening on Tuesday. Low-level convergence over the eastern
peninsula will likely get a boost from the sea- breeze component,
as the southwesterly low-level flow weakens and backs more
southerly near the east coast. As a result, could see more
widespread convective clusters and heavier rain farther east toward
the I-95 corridor, as supported by the higher HREF and RRFS
probabilities of 2-3 inch/hr rainfall rates across this area after
17Z Tuesday. Thermodynamic parameters will be more than supportive
for highly efficient warm rain processes, with mixed-layer CAPEs at
least 1000-2000 J/Kg, TPWs of 2.2-2.3", and wet bulb zero levels
above 14KFT (optimal warm layer depth). Moreover, 0-6km bulk shear
values around 20-25 kts should allow for more convective
organization, though the degree of downwind propagation
(southwesterly Corfidi vectors around 10-15kts) should inhibit the
potential for cell training.

As a result, any excessive short-term runoff on Tuesday will be
localized and likely tied to urban and/or poor drainage areas.

Hurley


Day 3
Valid 12Z Wed Sep 10 2025 - 12Z Thu Sep 11 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF
THE NORTHERN GREAT BASIN AND MUCH OF THE FLORIDA PENINSULA...

...Northern Great Basin east of the Cascades and Shasta Siskiyous
to central and northern Idaho...

Deep/closed upper low centered near the OR/CA/NV tri-state area
will average around 2 standard deviations below normal for early
September. Plenty of deep-layer Qs forcing (upper
difluence/divergence and periodic DPVA) will combine with above-
normal moisture (TPWs near 1.0" or 2-2.5 standard deviations above
normal) and sufficient diurnal instability (MUCAPEs 500-1000 J/Kg) to
produce locally excessive rainfall across portions of the northern
Great Basin Wednesday. The 00Z global guidance all show a modest
rainfall footprint, with the ensemble blends showing areal-average
totals between 0.50-1.00" within much of the outlook area.
However, largely tied to the degree of deep-layer instability and
available moisture, localized heavier totals were noted (2-4+
inches per the RRFS, GFS, and CMC), albeit with considerable areal
spread. The GEM in particular was most robust, noting a swath of
3-5+ inches across central OR east of Bend. For now, given the
spread in the guidance QPFs, will keep the ERO Risk at Marginal,
though this setup synoptically certainly would have the potential
for a more enhanced (i.e. Slight) risk as the event draws near.

...Florida Peninsula...

Similar setup to Tuesday, though the guidance shows a bit more
robust shortwave activity SW-NE across the Peninsula along and
south of the surface front which should remain quasi-stationary
across central FL on Wednesday. As a result, the multi-model
blend is higher with the QPF in terms of areal-average (ensemble
mean) on Wed compared to Tue, particularly over the central and
eastern portion of the peninsula where some backing in the low-
level flow (from the Atlantic sea breeze) will likely enhance the
low-level convergence due. Once again though given the downwind
propagation (S-SW Corfidi Vectors ~10+ kts), anticipate progressive
cell motions while not expecting much in the way of persistence or
training of the convection. Therefore the excessive rainfall risk
remains Marginal given the more isolated/localized risk for flash flooding.

Hurley
$$
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FOUS30 KWBC 100804
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
404 AM EDT Wed Sep 10 2025

Day 1
Valid 12Z Wed Sep 10 2025 - 12Z Thu Sep 11 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE URBAN I-95 CORRIDOR OF SOUTH FLORIDA...

...Florida...

A stationary front draped across north Florida will remain in place
as abundant tropical moisture, characterized by PWATs over 2
inches, streams across the state and along that front. Within that
moisture plume over much of the southern half of Florida, numerous
showers and thunderstorms are likely to form with peak heating
this afternoon. As on previous days, despite the front to the
north, over most of the peninsula, there are likely to be many
different sources of forcing for the storms. Without a coherent
source allowing the storms to organize, it's likely the storms will
remain individual or form into small clusters. While there will be
plenty of moisture for the storms to be capable of heavy rainfall
with any stronger core, without organization it appears unlikely
that for most of the peninsula, there will be more than isolated
instances of flash flooding.

Across the urban I-95 corridor, however, multiple prior days'
rainfall has thoroughly saturated any soils. Thus, when heavy rain
occurs with the afternoon and evening convection, there is more
likely to be widely scattered instances of flash flooding. Thus,
the Slight Risk area inherited remains unchanged with this update.

...Pacific Northwest...

A large upper level low and associated trough covering much of the
West Coast will gradually drift east/inland across the
Intermountain West today. Shortwave energy rotating around the low,
interacting with the instability caused by the cold air aloft and
unusually high amounts of atmospheric moisture (anomalies to 2.5
sigma above normal) will allow several clusters of showers and a
few storms capable of heavy rainfall to form. Upslope enhancement
may also locally increase rainfall rates as any clusters of showers
and storms move through. While some minor tweaks were made to the
Marginal, especially in northern California, the forecast remains
largely the same.

Wegman


Day 2
Valid 12Z Thu Sep 11 2025 - 12Z Fri Sep 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTH FLORIDA...

...Florida...

The stationary front plaguing Florida for well over a week will
begin to move as a cold front on Thursday, as a reinforcing shot of
cooler and drier air pushes south across the Southeast. As the
front pushes south down the Peninsula, the front should act as a
source of forcing for the storms, allowing for greater organization
and greater areal rainfall across South Florida as compared with
previous days when the forcing was far less defined. Add in the
saturated soils across south Florida, and the area where flooding
could be more frequent than isolated instances expands north up the
I-95 corridor towards the advancing front. Thus, the Slight was
expanded north accordingly.

...Pacific Northwest into the Northern Plains...

A plume of anomalously high moisture in place from the Pacific
Northwest to the Northern Plains will support scattered showers and thunderstorms forming once again along a corridor from eastern
Oregon through much of northern Montana. A separate cluster of
storms may sneak south across the Canadian border and into far
northeastern North Dakota and northwestern Minnesota as well. Due
to the potential for heavy rain in all of these areas, a Marginal
Risk is in place and has been expanded eastward to cover the areas
most likely to see isolated instances of flash flooding from heavy
rain from these features.

...Western Colorado and Far Northwestern New Mexico...

Southerly flow on the western edge of a low-level jet across the
Plains will transport Gulf moisture into the region on Thursday.
Meanwhile the large trough out west will become positively tilted
with time. This will allow an 80 kt jet southwesterly jet streak to
form, which will increase the divergence aloft across this area.
Expect upslope into the high peaks of southwestern Colorado to
locally enhance rainfall totals, thereby increasing the flash
flooding risk. Soil moisture measurements from NASA Sport show much
of this area to be below average/drier than normal. Thus, expect
much of the rainfall Thursday in this region to work to saturate
the soils in anticipation of Day 3/Friday's bigger rainfall event.

Wegman


Day 3
Valid 12Z Fri Sep 12 2025 - 12Z Sat Sep 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTH FLORIDA AS WELL AS FOR PORTIONS OF NORTHWESTERN NEW MEXICO
INTO SOUTHWESTERN COLORADO...

...Northwestern New Mexico into Southwestern Colorado...

A positively tilted longwave trough centered over much of the
Intermountain West on Friday will become more neutrally tilted on
Friday as a strong shortwave trough causes the southern half of the
trough to begin to race eastward. The result will be even more
enhanced upper level divergence out ahead of the trough over New
Mexico and Colorado. Atmospheric moisture will be largely unchanged
in this area from Thursday. With peak heating Friday afternoon,
numerous showers and thunderstorms will form over nearly all of the
High Plains. However, coverage and intensity will be much higher
in the Slight Risk area in Colorado and New Mexico. The area is
likely to be the same one hard hit from the Day 2/Thursday period,
so expect soil moisture amounts to be higher and FFGs to be lower
over much of the area by Friday's event. Given all of these
ingredients in place and in coordination with GJT/Grand Junction,
CO forecast office, a Slight Risk upgrade was introduced with this update.

...South Florida...

The cold front across central Florida at the start of the day
Friday will make slower, but still incremental progress in its
southward movement down the peninsula. The plume of tropical
moisture across south Florida ahead of the front will also still be
in place. Thus, as is similar to Thursday over the middle of the
state, the axis of heaviest moisture will simply shift southward to
far south Florida on Friday. The inherited Slight Risk area was
expanded west over much of the Everglades and portions of southwest
Florida with this update, to follow more closely to where the axis
of heaviest rainfall is likely to set up. Given the focus will
shift into the more vulnerable and flood prone urban areas of south
Florida, its entirely possible that a higher end Slight risk will
need to be issued for the Ft. Lauderdale to Miami corridor with
future updates.

...Northern High Plains...

Similar to Day 2/Thursday, anomalous moisture will remain in place
across much of Montana and portions of adjacent states again on
Friday. The upper level low and trough will move overhead or just
south of the region on Friday. As the cold air aloft peaks in depth
on Friday, numerous showers and thunderstorms are likely to
redevelop again on Friday afternoon with peak heating and maximum
instability. The axis of heaviest rain from central Idaho through
northwestern Montana will also be largely unchanged and unmoving
from Thursday, meaning these areas will likely have a second day of
showers and storms capable of heavy rain and flooding again on
Friday. Thus, here too a Slight Risk upgrade may be needed with
future updates. This will largely be determined by how much rain
falls on Thursday in this area, which will prime the soils for
Friday's round of rain.

Wegman
$$
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FOUS30 KWBC 110811
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
411 AM EDT Thu Sep 11 2025

Day 1
Valid 12Z Thu Sep 11 2025 - 12Z Fri Sep 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTH FLORIDA...

...South Florida...

A quasi stationary front over central Florida will make incremental
southward progress down the Peninsula today. Ahead of this source
of forcing, atmospheric moisture levels across south Florida remain
very high, with PWATs above 2 inches. With afternoon heating,
MUCAPE levels will once again rise to between 2,000 and 3,000 J/kg.
This will support numerous showers and thunderstorms developing
over the southern half of the state, and generally moving southward
through the afternoon. However, as is typical of Florida afternoon
convection, while the overall storm motion may be southward,
localized forcing such as cold pools and sea breezes may make
individual cell motion far more erratic. Given that soils across
much of the Florida Peninsula are fully saturated after weeks of
afternoon convection each and every day, this will still pose a
widely scattered flash flooding risk, particularly along the urban
I-95 corridor. However, given the saturated soils, the threat
extends into much of interior south Florida as well. The inherited
risk areas were trimmed from the north to eliminate most areas that
are already behind the front, and therefore much drier.

...Northwest...

An area of well above average moisture on the northwestern side of
a nearly stationary longwave trough/cutoff low over the
Intermountain West will act as a focus for additional shower and
thunderstorm activity in the typically dry areas from eastern
Oregon northeast through much of Montana. While the longwave trough
will be very slow-moving, the embedded shortwaves and vort maxes
circulating around it will be faster moving, providing additional
forcing and areas of divergence for any shower and thunderstorm
development. Local mountains and ranges will also work to cause
some thunderstorm development. Thus, due to there being several
forcing mechanisms with little to note as to which will be
dominant, expect multiple clusters of storms to develop this
afternoon with peak heating. With plenty of atmospheric moisture
available for those storms, many may be capable of heavy rainfall
which could quickly cause flash flooding, especially in any urban
areas, slot canyons, and narrow river valleys.

...Western Colorado into Northwestern New Mexico...

On the eastern side of the deep longwave positively tilted trough
in the west, increased divergence and lift ahead of that trough,
supported by southerly flow of moderate amounts of Gulf moisture
will support numerous showers and a few storms forming across the
Marginal Risk area today through tonight. The key to the flooding
potential in this area will be the long duration of mostly light
rain but that will be training in this Marginal Risk area from this
afternoon through much of tonight. The Marginal Risk area remains
largely unchanged from inherited.

Wegman


Day 2
Valid 12Z Fri Sep 12 2025 - 12Z Sat Sep 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTH FLORIDA AS WELL AS FOR PORTIONS OF SOUTHWESTERN COLORADO INTO
CENTRAL NEW MEXICO...

...South Florida...

The front across South Florida on Friday will make additional
progress southbound down the Peninsula. The portion moving down the
west coast of the peninsula will make better progress southward
compared to the portion of the front along the East Coast. This
should support the front becoming increasingly aligned southwest to
northeast. Since the front will be moving a bit more on Friday,
there should be a bit better coverage of storms across south
Florida, where the Slight Risk area inherited remains largely
unchanged. As the front pushes south, it will shove the bulk of the
tropical moisture into the Florida Straits and into the Bahamas.
This should work to limit storm coverage on future days, as a much
drier and cooler air mass continues to envelop the rest of the state.

...New Mexico and Colorado...

The positively tilted upper level trough from Thursday will begin
to pivot to become neutrally tilted on Friday. This means the
southern end of the trough will get a boost to advance eastward,
while the northern end will largely stay in place. The result will
be a more south to north oriented axis of heavy rainfall,
stretching from the southern end of New Mexico north across much of
western Colorado. Moisture from the Pacific will also be drawn
northward along the New Mexico/Arizona border. This should expand
the rainfall footprint for Friday across much of the southern
portion of New Mexico and southeastern Arizona. Expect Friday to
the wettest day this week for New Mexico and Colorado.

CAMs guidance suggests the plume of moisture stretching NNE from
southeast Arizona through north-central New Mexico and into
Colorado will be the focus for additional convection capable of
producing flash flooding. With better southward extent, the storms
will be able to tap into some deeper moisture and instability from
the Pacific on Friday. This will make thunderstorm coverage Friday
greater than in previous days. Since the whole plume will also be
lifting north and east, expect a much larger area of rain to impact
the area Friday. Embedded thunderstorms among the mostly lighter
shower activity will be the foci for any potential flash flooding.
This will be particularly true in any areas where multiple rounds
of storms producing heavy rain occur.

...Northwest...

Shortwaves and vorticity maxes rounding the periphery of the
longwave trough will be the foci causing additional convection from
northern Idaho east across much of Montana. The expected rainfall
forecast has decreased the overall rainfall in this area. However,
mountain forcing may offset this in some areas.

Wegman


Day 3
Valid 12Z Sat Sep 13 2025 - 12Z Sun Sep 14 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM EASTERN NEW
MEXICO THROUGH SOUTHWESTERN KANSAS, AS WELL AS FOR A PORTION OF THE
URBAN CORRIDOR OF SOUTH FLORIDA...

...New Mexico through Kansas...

As the upper level trough over the Intermountain West becomes more
negatively tilted, a portion of the low level jet out ahead it will
draw deeper Gulf moisture north into the Panhandles and eastern New
Mexico and into southwestern Kansas. This will support a line of
storms that will develop over central New Mexico and then press
eastward into the Slight Risk area. Once over eastern New Mexico
and the Panhandles, the eastward progress of the storms will
diminish greatly, resulting in much slower-moving but still
organized storms. This will be the basis for training, resulting in
widely scattered instances of flash flooding where the storms are
the most persistent.

...South Florida...

The front over South Florida will finally push east and clear all
of the deepest tropical moisture well out into the Atlantic and
Bahamas by Sunday morning. Thus, expect Saturday to be a transition
day in the area...where there will still be storms, particularly
along the urban I-95 corridor from Miami through Palm Beach, but
there will be less coverage over Florida as the moisture is pushed
eastward out into the Atlantic. The newly issued Slight is a low-
confidence one, as once the front clears the state, that should end
the flooding threat. However, given the many days of daily
afternoon convection in the I-95 corridor, soils are sensitive
enough that even the reduced time and coverage of storms could
still cause widely scattered instances of flash flooding.

...Northern Plains...

Across the Northern Plains, ahead of the neutrally tilted trough
that is becoming negatively tilted, the northern extent of the low
level jet ahead of the trough will draw deeper Gulf moisture
westward across the Dakotas. This should support persistent
convection. However, this area of the Dakotas is fairly difficult
to flood, so despite the higher probability for training and heavy
rain, the area remains in a higher-end Marginal for now. A Slight
Risk upgrade may be needed for portions of the area as guidance
begins to resolve this part of the event across the northern Plains.

Wegman
$$
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FOUS30 KWBC 120805
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
405 AM EDT Fri Sep 12 2025

Day 1
Valid 12Z Fri Sep 12 2025 - 12Z Sat Sep 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTH FLORIDA, SOUTHWESTERN COLORADO THROUGH CENTRAL NEW MEXICO,
AND THE NORTHERN PLAINS...

...South Florida...
Stationary front persists over far South Florida today with the
positive moisture anomaly focused over the Miami metro with the
eastern coast likely to get more slow moving heavy thunderstorms
in the light mean layer flow. The Slight Risk is shrunk to be
closer to the Miami-Palm Beach metro area with the Marginal Risk
still extending up the east coast nearly to Jacksonville.

...New Mexico and Colorado...
The positively tilted upper level trough from an upper low over
northern NV will pivot to neutral tilt this afternoon. Therefore,
expect a more south to north oriented axis of heavy rainfall,
stretching from south-central New Mexico to across much of western
Colorado. Moisture from the Pacific will also be drawn northward
into eastern Arizona and western New Mexico with PW anomalies of
+1.5 to 2 sigma, resulting in a rather large QPF footprint.
Diurnal convection is the main focus at play today, though
guidance continues to suggest repeating rains over southeast AZ and
southern NM into the overnight. The Slight Risk is maintained over
southwest CO and central NM.

...Northern Rockies onto the Northern Plains...
The upper low center shifts north to MT by late tonight. Notable
activity ahead of the low/trough looks to focus over the western
Dakotas into eastern MT per 00Z CAM consensus where a Slight Risk
has been raised. PW anomalies of 1 to 2 sigma remain over northern
ID/western MT where the Marginal Risk is maintained.

...Upper Midwest...
Ongoing activity over eastern ND and northern MN should shift
southeast by 12Z and track to northern WI. Then diurnally driven
convection looks to cross a similar path. Given the advance of
moisture over the upper ridge axis extending over eastern IA, it
was worth adding a Marginal Risk to northern MN/WI and the western
U.P. of MI.


Jackson


Day 2
Valid 12Z Sat Sep 13 2025 - 12Z Sun Sep 14 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM WESTERN KANSAS
TO FAR WESTERN TEXAS, THE MIAMI METRO, AND WESTERN NORTH DAKOTA...

...Central High Plains through Southern Rockies...
The upper level trough over the Intermountain West becomes
negatively tilted on Saturday with the monsoonal moisture axis over
NM during the day shifting to the southern High Plains overnight.
The position of this trough will enhance the low level jet on the
High Plains Saturday night and draw deeper Gulf moisture north
over the Panhandles and eastern New Mexico and through western
Kansas. This will encourage diurnally developing lines of storms
from New Mexico terrain to press eastward onto the High Plains.
Given the +2 sigma PW anomalies and overall slow storm motion, the
Slight Risk area was expanded a bit over western KS and down into
far western Texas.

...South Florida...
The front will push south from Florida during the day Saturday with
anomalous moisture lingering in the morning over the Miami metro
where A Slight Risk persists. The Slight Risk still looks generous
given the decreasing moisture profile through the day, but is
maintained for now.

...Northern Plains...
The upper low center over central MT will allow the focus for
heavy convection to shift north a bit from Friday with both morning
and diurnal max activity looking to focus on western ND. Given good
overlap in heavier precip among available CAMs and the EC-AIFS, a
Slight Risk is raised over western ND. Pivoting of the low without
much lateral movement is expected, prolonged heavy rainfall is
possible with.

Jackson


Day 3
Valid 12Z Sun Sep 14 2025 - 12Z Mon Sep 15 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN THE DAKOTAS...

...Central and Northern Plains...
Negatively-tilted trough axis lifting up the central Plains Sunday
should provide a narrow focus to convective development over the
western or central Dakotas. This activity will be heavy given PW
anomalies of +3 sigma persist over this area. Further development
is expected from central KS up through the Dakotas where a generous
Marginal Risk remains in effect.

Jackson
$$
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FOUS30 KWBC 130849
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
449 AM EDT Sat Sep 13 2025

Day 1
Valid 12Z Sat Sep 13 2025 - 12Z Sun Sep 14 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR EASTERN NEW
MEXICO INTO FAR WEST TEXAS AS WELL AS FOR WESTERN NORTH DAKOTA...

...Central High Plains through Southern Rockies/West TX...

Upper trough over the Great Basin this morning will continue
slowly eastward and take on a negative tilt, with a continued
influx of moisture (PW anomalies +2 sigma) into the Southern
Rockies and points northward. As the trough axis crosses the Four
Corners region around 00Z tonight, LLJ increase will support
convection over eastern NM late afternoon that will push into West
Texas in the evening. Storms may have enough forward speed to limit
flash flooding potential, but 00Z CAMs continue to show potential
for 1-4" amounts. Focused the Slight Risk outline further from the
previous shifts to the best ensemble agreement.

...Northern Plains...

Southerly flow through the column will maintain a surge of
moisture (PW anomalies +3 sigma / 1.50") into the Northern Plains
as weaker shortwaves race northward ahead of the main upper low
over MT. Recent CAM guidance still shows some east-west
displacement of heaver north-to-south QPF maxima, owing to small
differences in shortwave/sfc boundary interactions and any morning
convection. Maintained the Slight Risk outline over western ND but
the eventual QPE footprint will likely be much narrower.

...Northeastern Illinois and surrounding areas...

Shortwave diving southeastward out of Wisconsin this morning at
the nose of a jet streak will help organize a small area of at
least modest rainfall around the Chicagoland area that continues
SSE-ward this afternoon. Some 00Z CAM guidance remains rather
bullish with 2-3" amounts which may be enough to cause some urban
runoff issues.

...South Florida...

Frontal boundary will remain just to the southeast of Florida, but
precipitable water values will start the day around 2 inches.
Drier air will slowly work southeastward through the entirety of
the Peninsula by the end of the day, and have targeted the Marginal
Risk outline to around the urban areas between Palm Beach and Miami.

Fracasso


Day 2
Valid 12Z Sun Sep 14 2025 - 12Z Mon Sep 15 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN THE WESTERN DAKOTAS...

...Central and Northern Plains...

Upper trough exiting the Rockies will split off its southern
portion into an upper low over western Nebraska midday Sunday, with
southerly flow continuing across the Northern Plains (and ample
moisture -- PW anomalies still +2 to +3 sigma). This mid-level low
will lift northward and act as a focus for convergence toward the
nose of the sfc- based instability gradient just to the east.
Storms may repeat over the same area as D1, with the potential for
another 1-2"+ of rain. Maintained the Slight Risk outline here with
a broader Marginal Risk extending to the south where the guidance
shows potential for 2-4" of rainfall, but over areas with higher
FFG values (esp. the Sand Hills).

Fracasso


Day 3
Valid 12Z Mon Sep 15 2025 - 12Z Tue Sep 16 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Fracasso
$$
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FOUS30 KWBC 140824
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
424 AM EDT Sun Sep 14 2025

Day 1
Valid 12Z Sun Sep 14 2025 - 12Z Mon Sep 15 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN THE WESTERN DAKOTAS...

...Northern Plains...

Upper trough exiting the Rockies has split off its southern
portion into an upper low that will move onto the High Plains later
this morning. Southerly flow will continue across the Northern
Plains along with ample moisture -- PW anomalies +2 to +3 sigma --
as a surface low over SD moves northward later this afternoon.
Convergent flow toward the nose of the sfc-based instability
gradient just to the east is expected to promote some south-to-
north convection that may overlap areas that saw a few inches of
rain on Saturday. Maintained the Slight Risk outline here with a
Marginal Risk buffer extending to the south to the edge of the Sand
Hills.

...Central and Southern Plains...

Split the longer Marginal Risk area from the previous forecast
into its own entity and extended it even farther southward to the
Mexican border to account for another tick up in expected
convection from KS southward to TX. Storms should fire along and
ahead of a low-level confluence axis and within a stripe of deeper
moisture. Some of these areas in W TX saw a couple/few inches of
rain on Saturday and FFG values are lower. Some models do indicate
the potential for slow-moving or backbuilding cells, resulting in
locally heavy amounts and perhaps isolated flash flooding concerns.

Fracasso


Day 2
Valid 12Z Mon Sep 15 2025 - 12Z Tue Sep 16 2025

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Fracasso


Day 3
Valid 12Z Tue Sep 16 2025 - 12Z Wed Sep 17 2025

...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL IN SOUTHERN NEW
MEXICO, THE CENTRAL PLAINS, AND COASTAL VIRGINIA...

...Southern New Mexico...

Moisture will start to nudge upward over southern NM (though much
more well west of there) with some afternoon instability and
expected isolated convection, mainly over the mountains close to
the Mexican border. Low-end Marginal Risk is outlined here though
activity should be rather isolated.

...Central Plains...

Positively-tilted trough over the Northern Rockies will move
eastward to the High Plains Tuesday afternoon. Broad westerly mid-
level flow amid increasing moisture will help fire off some storms
over at least NE near the better forcing but also southward into
KS. A Marginal Risk is outlined here for an isolated flash flood
threat.

...Coastal Virginia...

Over the past couple of days, the models have trended toward
bringing in an area of low pressure near the Outer Banks Tuesday
morning or so. Rain should spread inland on Monday with additional
and perhaps heavier rain on Wednesday. This area has been rather
dry recently and rain rates may not be all that high, but some convection-driven rain is possible depending on the flavor of this
area of low pressure. A Marginal Risk is depicted for
southeastern/coastal Virginia and far northeastern North Carolina
but with a lot of uncertainty in the rainfall
pattern/rates/duration.

Fracasso
$$
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FOUS30 KWBC 150743
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
343 AM EDT Mon Sep 15 2025

Day 1
Valid 12Z Mon Sep 15 2025 - 12Z Tue Sep 16 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
EASTERN NORTH CAROLINA AND SOUTHEASTERN VIRGINIA...

Current WV satellite indicates a maturing mid-level trough situated
just off the SC/GA coast with a surface low analyzed 150 miles
east of KILM, meandering around as the upper pattern evolves.
Expectation is the surface low to be pulled northwest over the
course of the D1 with a closer proximity to the NC coast by later
this afternoon and evening with a strong east to northeast flow
anticipated over the northern flank of the SLP. Current NAEFS
ensemble output is forecasting a stout +2/+3 deviation u-vector
wind component with origins straight off the Atlantic, a signal
coincident with a robust low-level moisture advection regime into
the northern and western flank of the low pressure center. PWATs
are anticipated to climb closer to +1.5 deviations above climo,
good enough for outputs within the 1.5-2" mark across much of
eastern NC into the VA Tidewater. The persistence in the low-level
flow and modest ascent located within the maturing deformation axis
will lead to a long period of heavy rainfall situated across the
aforementioned areas above, allowing totals to reach between 2-4"
over areas along and east of I-95 and north of US70 in NC, and
between 1-3" across the VA Tidewater.

00z HREF is pretty robust in the depiction for the above totals
forecast with some embedded convective elements likely to spur
rates between 1-2"/hr at times, mainly across northeast NC where
strongest 850-700mb FGEN signals align early this evening into the
overnight hours. HREF neighborhood and EAS probs for >2" are pretty
high for the region with the neighborhood >3" signal settling
between 50-90% for the zone referenced above in NC. Antecedent
drier soils leading in will help curb some of the flash flooding
concerns initially, but the long-standing heavy rain threat, and
embedded convective potential the second half of the forecast could
lead to isolated/scattered bouts of flash flooding as the event
continues. The previous MRGL risk was expanded to align with the
trends in the >3" neighborhood prob signal in the HREF, and to
account for the latest ECMWF EFI signal extended a bit further west
than where we had the previous MRGL risk located.

Kleebauer


Day 2
Valid 12Z Tue Sep 16 2025 - 12Z Wed Sep 17 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHWEST, THE CENTRAL HIGH PLAINS, AND VIRGINIA/NORTH CAROLINA...

...Southwest...

Scattered convective pattern will initiate on Tuesday afternoon and
early evening before fading with the loss of diurnal heating.
Current progs are for convection to be tied closer to the terrain
across southeast AZ into southern NM with isolated signatures of

1"/hr plausible in the stronger cell cores. These areas generally

prone to runoff due to terrain complexities, as well as remnant
burn scars present in some locations. Maintained continuity from
inherited MRGL risk with some minor adjustments to remove El Paso proper.

...Central High Plains...

Strong shortwave trough ejection out of the interior Northwest will
lead to convective development and regional enhancement across the
Central High Plains. Greatest ascent is aligned with the diffluent
region of the mid-level shortwave with left-exit region dynamics
likely to maintain a prevalent heavy rain signature across the
western third of NE down into neighboring northeast CO and
northwest KS. Heaviest rain could remain just outside of the risk
area according to some guidance leading to low probability of flash
flooding due to the occurrence within the western Sand Hills.
There's still a good agreement on localized maxima within the hi-
res ensemble means, pin-pointing the area west of North Platte, NE
as one of the favorable spots for convective impacts. FFG's in this
corridor are lower than the neighboring Sand Hill domain, so the
MRGL risk remains relatively small.

...Virginia and North Carolina...

Our surface low will mature and occlude by Tuesday afternoon as the
closed height fields indicate the 850/700/500 mb lows becoming
vertically stacked leading to a slow decay of the surface low by
the second half of the period. Persistent heavy rain potential will
linger across eastern NC up into the VA Tidewater leading to
multi-day totals reaching 2-4" with locally upwards of 6-7" over
the span of 48 hrs. Despite the drier soils leading into the event,
the cumulative effect will lead to areal flooding concerns for
portions of the above locations. Some westerly push of the heavier
QPF is progged in the front half of D2 leading to some areas in
north-central NC up through south-central VA possibly sneaking into
the flash flood threat. The only good news is the weakening surface
low will lead to degrading rates eventually, and slow wane on the
threat. The MRGL risk inherited was maintained with some minor
westerly expansions to account for recent trends in the ensemble means.

Kleebauer


Day 3
Valid 12Z Wed Sep 17 2025 - 12Z Thu Sep 18 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PARTS OF THE
NORTHERN AND CENTRAL PLAINS, SOUTHERN HIGH PLAINS, AND SOUTHEAST FLORIDA...

...Northern and Central Plains...

A strong mid-level shortwave trough will eject into the WY Front
Range and eventually close off across NE generating a maturing lee
cyclone across the Central High Plains. The setup will likely cause
quite a robust deformation signature on the northwest flank of the
cyclone with ensemble mean QPF placement situated over western NE
up through southwestern SD, arcing back into the nose of the warm-
conveyor belt on the northeast side of the system. This is a
classic mid-latitude lee cyclogenesis setup with a strong jet
coupling leading to broad large scale forcing and widespread precip
across the Plains. Eastern side of the cyclone will exhibit the
best convective potential while the deformation axis provides a
solid precip field with moderate to locally heavy rates for several
hrs. in that northwest side of the low. Totals >2" are forecast
within the means across western NE into SD with scattered elevated
QPF across the Missouri River basin located in eastern SD and NE.
This setup is conducive for at least some isolated to scattered
flash flood prospects considering the synoptic evolution. This was
enough to warrant a MRGL risk in those areas deemed the best chance
for heavy rain prospects.

...Southern High Plains...

Maturing lee side low to the north will help drag a trailing cold
front through the Central and Southern High Plains on Wednesday.
The front will slip south and southwest once down near the
latitude of the OK Panhandle, leading to a more textbook backdoor
frontal progression as it enters into the northern TX Panhandle and
northeast NM. Flow begins to run more parallel to the boundary in
these zones when assessing forecast soundings from relevant global deterministic. The key in the setup is a relatively solid
isentropic ascent pattern in a small zone bordering CO/OK/NM/TX
with cross-section views over the area displaying a classic sloped
low-level surface FGEN with strong omega correlating to rapid
ascent as the front progresses through the area. Locally enhanced
corridor of precip will transpire along and in wake of the front
with local maxima of 1.5" to as much as 3" plausible during the
event. This could be enough for an isolated flash flood threat,
especially in those smaller urban areas situated across the 4 state intersection. A MRGL risk has been added to account for the threat.

...Southeast Florida...

Stalled front with an enhanced moisture return across South FL will
lead to a heightened threat for flash flooding over the urban
centers of southeast FL. Deterministic output is scattered in the
exact location of the heaviest precip, ranging from the Keys up to
West Palm Beach and everywhere in-between. The setup is
historically favorable for flash flood concerns over the urban
zones of southeast FL with PWATs hovering between 2-2.3", a solid
1/1.5 deviations above normal. In coordination with the Miami WFO,
a MRGL was maintained for that urbanized coastal corridor between
West Palm down to Miami proper since this is the most likely
location for flash flooding in this type of setup. Will monitor
convective trends as we get closer to see if this necessitates any
expansion, or even a targeted upgrade.

Kleebauer
$$
d
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FOUS30 KWBC 180802
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
402 AM EDT Thu Sep 18 2025

Day 1 Valid 12Z Thu Sep 18 2025 - 12Z Fri Sep 19 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF
SOUTHERN CALIFORNIA AND SOUTHWESTERN ARIZONA...

...Southwest U.S...

Remnant moisture from post-tropical cyclone Mario will continue to advect poleward with California firmly in the cross-hairs for elevated
moisture (PWATs 2-4 deviations above normal) to move into the
southern half of the state during the entirety of the D1 period.
Energy from Mario will lag the initial low to mid-level moisture
surge, but eventually will enter into the area by the late-morning
hours today, prompting an uptick in the areal coverage of
convection over the southern half of the state into the Lower
Colorado Basin between CA/AZ. The last succession of HREF runs,
including this evenings 00z suite was pretty pronounced in the
indication of precip totals between 2-4" potentially impacting some
of the coastal ranges of CA into the adjacent valley just north of
the Transverse and Peninsular Ranges. There's also a pretty good
indication of scattered to widespread convective development later
this morning, through the afternoon period across the lower deserts
of southeast CA to the neighboring Colorado Basin at the CA/AZ
line. This was the area of greatest change when it came to the
magnitude of the signal when assessing the run to run differences
over the past iterations of the HREF suite. Ensemble bias corrected
QPF was also adjusted upward from its previous forecasts across the aforementioned area, a testament to the improving signature for
local flash flood prospects in that general area. HREF neighborhood
probs for >1" across the deserts are upward of 50-80% now with
70-90+% located within the Transverse and Peninsular Ranges during
the period, a reflection of the heightened threat for at least
moderate rainfall, enough to spur high runoff concerns in the
terrain with several burn scars still present in-of those mountain
chains. Rates will be sufficient considering the deep moist
environment brought on by the advection of the tropical moisture
flux involved with Mario, another reason for the threat to be
leaning towards the higher side as elevated rates are a significant
driver to flash flooding historically across CA.

The previous SLGT was expanded a bit to account for the trends in
hi-res guidance and the conditioning of the environment favoring
the higher moisture anomalies being advected further north into CA.
The threat is on the higher end of the SLGT threshold with the
"saving grace" in this entire setup being the more progressive mean
flow helping push everything through in relatively faster time than
what is customary for higher level risks. That still doesn't deter
the fact that scattered flash flood prospects are becoming more
certain in the the areas outlined in the SLGT risk with a potential
for targeted upgrade plausible if conditions warrant.

...Central U.S...

Current WV satellite depicts a broad upper low (ULL) with the center
positioned over SD with a surface low analyzed almost underneath
the ULL meaning the confidence in an occlusion process beginning
soon is very high. Once we see the occlusion phase begin, we'll see
the slow degradation of the prominent deformation field across the
Dakotas over the course of the forecast leading to decreasing
rates and expected totals compared to what transpired the period
prior. As a result, flash flooding concerns will be relatively
isolated given the more stratiform rain process with the convective
threat positioned further east into the Mississippi Valley. 00z
HREF was not very robust for heavy rain prospects in any one area,
but there were several locations that will stand to benefit from
locally heavier convection as the cold front continues to migrate
eastward and drive a broad surface ascent pattern downstream of the
low. A few stronger mid-level vorticity maxima will help amplify
the threat in a few areas, mainly in the Missouri and Mid-
Mississippi Valleys later this afternoon as a stronger mid-level
shortwave continues to propagate into the region from its overnight
trajectory. HREF blended mean QPF distribution outlines this area
fairly well and matches with the modest >3" probabilities situated
over eastern OK up into MO. Overall, the entire setup with a slowly
decaying, or steady state low will contribute just another period
of widely scattered flash flood prospects from the Northern Plains
over and through the northern two-thirds of the Mississippi Valley.
The previous MRGL was general maintained with some adjustments
based on the latest hi-res ensemble probs and blended mean QPF footprint.

...Southeast Florida...

PWATs across south FL remain elevated with KEYW and KMFL both
coming in with values of 2.08" and 2.19", respectively meaning the
deep layer moisture forecast the past several days is firmly
entrenched over the region. Several shortwave perturbations will
advect northeast out of the Florida Straits and nearby Cuba with
the presence of a Cuban outflow being picked up in the radar/sat
composite over the past few hours. This is actually well-forecast
via some of the CAMs suite, a likely indicator that the future
trends within the models probably hold merit for a threat of heavy
rain to cross into the Key and the southern Peninsula in the early
morning hours. As the boundary migrates to the northeast, expect
copious showers/storms to gallivant through the area dropping
locally enhanced rainfall with rates between 2-3"/hr pretty much a
given in a few of the convective cores just due to the environment
in place. Models are still in flux on the exact locations of where
heavier rain will occur, but the neighborhood probs for >3" running
between 50-80% and >5" between 25-35% across both the Keys and
southeast FL are sufficient for a continuation of the previous MRGL
risk through the forecast cycle. Will monitor closely for potential
targeted upgrades, but the setup is certainly favoring at least
isolated flash flood potential within those two corridors,
particularly more urban zones due to impervious surface runoff.

Kleebauer


Day 2 Valid 12Z Fri Sep 19 2025 - 12Z Sat Sep 20 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE
CENTRAL SIERRA NEVADA AND CENTRAL VALLEY OF CALIFORNIA...

...California...

Remnant energy from what is left over from Mario will pivot up into
Central CA early Friday allowing for a continuation of heavy
rainfall prospects over the region as PWATs surge to between 3-4
deviations above normal. Guidance is keying on prevailing upslope
flow and focused ascent within the Central Sierra of CA with a
myriad of thunderstorms lingering in the Central Valley. The
environmental conditions favor locally enhanced convective cores
which could spell problems for those towns in the valleys, as well
as runoff in the terrain. HREF neighborhood probs for >1" are very
high (70-90%) within the above areas with mainly modest >2" probs
centered over the Central Valley and adjacent Sierra foothills.
Considering some overlap of heavy rain from D1 into D2, the threat
seems worthy of a targeted upgrade in these two zones to account
for the continued risk bleeding from period to period. The good
news is the setup looks to wane the second half of the forecast
cycle as energy pushes out of the region and we see a slow
improvement in the moisture anomalies. This would spell the end
for the threat of flash flooding and much of the rain prospects.

...Southwest...

Moisture increases across all of the Southwest CONUS will aid in
favorable environmental conditions for locally heavy convective
rainfall during the period of diurnal heating on Friday into early
Saturday. HREF mean QPF is relatively tame overall, but some of the
CAMs are more robust in their depictions of isolated 2+" totals,
especially across the Mogollon Rim and Southeast AZ terrain leading
to a broad MRGL risk maintenance from previous forecast. The
threat for flash flooding will likely lie as far north as the
I-70/15 junction and points west over UT/NV with slot canyons and
dry arroyos as the primary targets for flash flooding as is
customary in these setups. The threat for a targeted upgrade is on
the table, but will need to assess the evolution of the mid-level
vorticity maxima ejecting out of CA to the east over the course of
time. The most favored areas will likely be those outlined above.
For now, the MRGL risk will suffice.

...Mississippi Valley to ArkLaTex...

Occluded low over the Upper Midwest will continue to spin with a
dumbbelling mid-level shortwave pivoting southeast out of the
Dakotas allowing for a secondary broad ascent pattern to
materialize downstream over the Mississippi Valley. To the south,
thunderstorms will fire along a decaying front positioned over the Mid-Mississippi Valley down into the ArkLaTex with ample
instability and moisture to fuel another isolated flash flood
threat when assessing individual CAMs and ensemble bias corrected
outputs. The threat is similar to the previous period, perhaps even
a touch less robust considering the occlusion phase well in
progress by this point in the forecast. Overall, this threat was
deemed enough for a broad MRGL risk to stay in place, but there's
some potential for a targeted upgrade, pending better overlap from
model guidance on any particular area from TX to the Upper Midwest.

...Southeast Florida...

The southeast coast of Florida will be hanging on to the last bit
of remaining anomalous moisture as the pattern starts to shift away
from persistence of the preceding three periods. The MRGL was
maintained given some of the guidance hanging on to heavier
convection right along the coast with modest probabilities for >3"
lingering from Miami up to Daytona Beach. That was enough to
maintain continuity of a MRGL for at least one more period.

Kleebauer


Day 3 Valid 12Z Sat Sep 20 2025 - 12Z Sun Sep 21 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE CENTRAL AND SOUTHERN PLAINS INTO THE MISSOURI VALLEY...

...Central U.S...

Shortwave ejection out of the Great Basin/Four Corners area will
migrate into the Central and Southern Plains by Saturday afternoon
providing a more focused large scale ascent pattern during peak
diurnal instability. Ensemble means are relatively modest in their
QPF distribution and magnitude, signaling 1-2" of rainfall
currently in their depictions. Individual deterministic is
certainly a little more robust, but nothing that would promote a
more substantial risk. This correlates well with moisture anomalies
hovering between normal and +1 deviations when assessing the latest
NAEFS meaning the threat is warranted, but well-within the
threshold of a MRGL risk. As a result, kept the previous MRGL risk
and expanded to account for some uncertainty in the spatial
coverage of expected convection by this time frame.

Kleebauer
$$
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FOUS30 KWBC 190811
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
411 AM EDT Fri Sep 19 2025

Day 1
Valid 12Z Fri Sep 19 2025 - 12Z Sat Sep 20 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE
CENTRAL SIERRA NEVADA...

...California/Great Basin...

Remnant energy from Mario will continue to lift north across
California and become sheared by an upstream low over the Pacific,
with some energy wrapping back offshore, while the remainder
moves east into the Great Basin. This energy, along with highly
anomalous moisture (+4 std dev above normal), is expected to
continue to produce showers and storms early in the period across
parts of California, including the Sierra Nevada. While forecast amounts
have trended down, there is still some signal for locally heavy
rain to continue early in the period across portions of the central
Sierra Nevada. A small Slight Risk was maintained, mostly for the
initial 6-hours, where the HREF shows higher probabilities for
additional amounts exceeding an inch. By the afternoon, as the mid
level energy and greater moisture anomalies move east, expect the
greater chance for heavier rain to begin to focus over central
Nevada, where the HREF is showing a broader footprint of high
probabilities for amounts over an inch.

...Southwest...

Expect widespread coverage of showers and storms today, as moisture
from Mario bolsters PWs across the region. The general consensus of
the CAMs show greater coverage across eastern Arizona and western
New Mexico during the afternoon, before storms move southeast into
southeastern New Mexico and West Texas by this evening. Storm
motions are expected to generally progressive, limiting the threat
for widespread heavy amounts and flooding. However, there is some
signal for backbuilding and training, which could raise at least
isolated runoff concerns. HREF neighborhood probabilities for
amounts exceeding an inch are above 50 percent within much of the
Marginal Risk area.

...Upper Mississippi Valley/Midwest to the Lower Missouri Valley...

A mid-to-upper level low/negatively-tilted upper trough will
continue to move slowly east from the northern Plains into the
upper Mississippi Valley this period. While not expected to be a
widespread heavy rainfall event, south-to-north training storms
ahead of the associated occluded front, may produce locally heavy
amounts and isolated flooding from northern Illinois back across
the upper Mississippi Valley. The HREF shows widespread high
probabilities for amounts exceeding an inch across this region,
with some localized high probabilities for amounts over two inches.

Meanwhile, shortwave energy diving southeast out of the northern
High Plains, is expected to produce a secondary area of organized
amounts, with some locally heavy amounts possible from
southeastern Nebraska into southwestern Iowa and northwestern
Missouri this evening into the overnight. Here also, the HREF is
showing high probabilities for amounts over an inch, with heavier
amounts possible.

...Central Plains...

Energy moving through the base of the previously noted upper
trough, interacting with deepening moisture along a strengthening
low level jet is expected produce showers and storms developing
and dropping southeast across Kansas, with locally heavy amounts
possible by this evening. HREF probabilities indicate localized
amounts of an inch or more are likely, with heavier amounts
possible.

Pereira


Day 2
Valid 12Z Sat Sep 20 2025 - 12Z Sun Sep 21 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF SOUTHEASTERN KANSAS AND NORTHEASTERN OKLAHOMA THROUGH THE OZARKS...

Storms developing late in the previous period across Kansas may
continue, producing locally heavy amounts across portions of the
Ozark Region Sunday morning. Redevelopment is possible back to the
west later in the day as shortwave energy emanating from the west
moves into the region and interacts with deepening moisture
afforded by strengthening southerly flow.

Pereira


Day 3
Valid 12Z Sun Sep 21 2025 - 12Z Mon Sep 22 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHWEST AND FROM THE OZARKS THROUGH THE MID MISSISSIPPI VALLEY...

...The Southwest...

An upper low off of the California coast will drift southeast,
supporting the return of deeper moisture spreading north across
Arizona and western New Mexico on Sunday. With PW anomalies
increasing to 2-3 standard deviations above normal, numerous showers
and storms, producing locally heavy rainfall amounts and isolated
flooding concerns, can be expected.

...Ozarks through the Mid Mississippi Valley...

A broad upper trough will drift slowly east from the Plains into
the Mississippi Valley this period. A series of mid level
shortwaves lifting along the leading edge of the trough,
interacting an axis of deeper moisture is expected to produce showers
and storms with periods of heavy rainfall possible.

Pereira
$$
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FOUS30 KWBC 200821
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
421 AM EDT Sat Sep 20 2025

Day 1
Valid 12Z Sat Sep 20 2025 - 12Z Sun Sep 21 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE MIDWEST, THE SOUTHERN PLAINS, OZARKS, AND THE CENTRAL
APPALACHIANS...

...Wisconsin and northern Illinois...

A negatively-tilted upper trough will lift slowly across the mid to
upper Mississippi Valley today. The associated ascent interacting
with a ribbon of relatively deeper moisture (PWs 1.25-1.5 inches)
along a modest low level jet will support showers and storms
redeveloping this afternoon, which may potentially continue into
the evening. With differences in the details, the CAMs generally
indicate two areas of locally heavier amounts -- a north-south axis
associated with storms lifting across eastern Wisconsin during the afternoon/evening and a west-east stripe produced by storms
developing across Iowa and then training across northern Illinois
later during the overnight. HREF neighborhood probabilities
indicate localized amounts in excess of 2 inches are possible in
these areas.

...Ozarks to southwestern Oklahoma....

CAMs indicate that ongoing convection firing north of a stationary
front over southern Kansas will continue through the late morning,
potentially producing heavy amounts as they train further east
into the Ozark Region. The HREF shows high neighborhood
probabilities for accumulations over 2 inches centered over this
region.

Then, as upstream energy sliding southeast across the central
Plains interacts with deepening moisture that will be supported by
increasing southerly low level flow, some guidance indicate that
storms will redevelop over this same area later today. However,
other models show storms developing further to the west before
moving back into areas impacted by this morning's storms.

While there is fair amount of uncertainty on how these storms
across central into eastern Oklahoma will evolve, there is greater
model consensus that storms developing over the Texas Panhandle and
western Oklahoma by this evening will merge across southwestern
Oklahoma to produce locally heavy amounts across the region during
the overnight.

...West Virginia...

CAMs continue to show isolated heavy amounts associated with slow-
moving storms that are expected to develop over eastern West
Virginia this afternoon. A weak impulse lifting northeast out of
the Ohio Valley, interacting with pooling moisture along a slowing
front, will support storm development. HREF neighborhood
probabilities indicate that amounts of 2-3 inches are likely within
the highlighted area.

Pereira


Day 2
Valid 12Z Mon Sep 22 2025 - 12Z Tue Sep 23 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE CENTRAL PLAINS, MID MISSISSIPPI VALLEY, AND THE SOUTHWEST...

...Eastern Kansas and northeastern Oklahoma to southern Illinois...

Deepening moisture (PWs above 1.5 inches) along an axis of
strengthening southerly to southwesterly flow ahead an amplifying
upper trough will fuel showers and storms, possibly producing
heavy amounts. While models differ significantly on the details,
the general consensus indicates widespread precipitation is likely,
with locally heavy amounts of 1-2 inches possible.

...Southwest...

An upper low dropping to the south along the California coast will
slow as it becomes cutoff west of Southern California. Southerly
flow ahead of the system will support increasing moisture and the
chances for precipitation across parts of Southern California and
Arizona. Both the GFS and ECMWF show PW anomalies increasing to 2.5
to 3 standard deviations above normal across far Southern
California through the lower Colorado Basin into Arizona.

Pereira


Day 3
Valid 12Z Mon Sep 22 2025 - 12Z Tue Sep 23 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHWEST AND FROM KANSAS AND OKLAHOMA TO THE OHIO VALLEY...

...Kansas and Oklahoma to the Ohio Valley...

Unsettled weather will continue, with the footprint for potentially
heavy rain expanding as energy moving through the base of a broad
upper trough interacts with deep moisture that will be supported
persistent southwesterly flow. While models generally agree on a
large footprint of moderate to heavy amounts, they lack agreement
on the details. At least locally heavy amounts are expected,
especially within the western portions of the highlighted area as
a well-defined shortwave dives southeast and is expected to
interact with a pool of deepening moisture along a strong
southwesterly low level jet. Given the indication of 2-3 inches in
some of the models, which is forecast to fall in addition to the
previous days' amounts, an upgrade to a Slight Risk may be
forthcoming if the signal persists and the guidance moves into
better agreement.

...Southwest...

An upper low is forecast to remain cutoff and drift slowly east
along the Southern California coast. Anomalous moisture in place
across Arizona is expected to spread east into parts of New Mexico,
extending the chances for showers and storms, with potentially
heavy amounts into the region.

Pereira
$$
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FOUS30 KWBC 210821
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
421 AM EDT Sun Sep 21 2025

Day 1
Valid 12Z Sun Sep 21 2025 - 12Z Mon Sep 22 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN THE VICINITY OF
THE KANSAS/OKLAHOMA/ARKANSAS/MISSOURI BORDER AREA...

...Central-Southern Plains into the Mid Mississippi Valley...
Additional shortwave energy will be diving east southeastward
through the base of the mean trof centered through the Central to
Southern Plains into the Middle Mississippi Valley. These height
falls will help strengthen the low level west south west to
southwesterly flow into a west to east northeasterly oriented low
level boundary stretching from the Southern Plains into the Middle
Mississippi Valley. This will support another round of convection
pushing east from central to eastern KS/OK into much of MO,
northwest AR and central to Southern IL. A slight risk area was
added in the vicinity of the KS/OK/AR/MO border area that has seen
heavy rains over the past 24 hours and may see additional heavy
totals later in the upcoming day 1 period. Otherwise, there were no
significant changes made to the previous marginal risk area, that
continues to fit well with the latest axis of high HREF
neighborhood probabilities for 1 and 2"+ amounts during the
upcoming day 1 period. Across these areas, relative soil moistures
remain very low, which should help mitigate runoff issues, at least initially.

...Southern California into Arizona...
The closed low initially off the Central California coast will be
drifting only slowly southward day 1 to a position off the
Southern California coast. A jet streak on the eastern side of this
upper trof will keep favorable right entrance region jet dynamics
over Southern CA into Arizona. This will help accentuate lift in
an axis of anomalous PW values, 1 to 3+ standard deviations above
the mean that are expected to persist across these areas day 1.
This should support potential for additional widespread scattered
convection, locally heavy rains and isolated runoff issues.

Oravec


Day 2
Valid 12Z Mon Sep 22 2025 - 12Z Tue Sep 23 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE
CENTRAL TO SOUTHERN PLAINS, MIDDLE TO LOWER MISSISSIPPI VALLEY AND
OHIO VALLEY AND ACROSS ARIZONA INTO WESTERN NEW MEXICO...

...Mid to Lower Mississippi Valley into the Ohio Valley...
The height falls pushing east southeastward day 1 into the Central
to Southern Plains and toward the Mid Mississippi Valley will
continue to move eastward through the Ohio Valley day 2. Well
defined large scale lift in an axis of above average PW values, 1
to 1.5+ standard deviations above the mean, will support the
likelihood of widespread moderate to heavy precipitation in an
axis from northern AR, far southeast MO, far southeast IL, western
to central KY, much of IN and OH. At the moment the convection
across these areas may be fairly progressive. This and very low
relative soil moistures, much of the area in moderate to severe
drought, will keep the risk level at marginal for the time being.
With respect to changes to the previous issuance, the northern edge
of the marginal risk was trimmed to the south by about 50-75 miles
to account for the latest model consensus.

...Central to Southern Plains...
The marginal risk area from the previous issuance was expanded
slightly westward into western KS to cover the model spread with
the next round of convection forming ahead of the upstream
amplifying height falls dropping southeastward late
day 1 from the Northern Rockies into the Central Rockies/Lee of the
Central Rockies on day 2. The GFS and NAM begin to diverge day 2
with the track of this closing off mid to upper level center, with
the NAM taking a more southeastward track into the Central Plains,
while the GFS takes a more south southeastward track into the
Central Rockies. The NAM solution, at the moment, is an outlier
with the EC, UKMET and CMC more in line with the GFS. The
differing mid to upper evolutions have more of a qpf impact over
south central WY into north central CO, where the more southeast
NAM solution is much lighter than the remainder of the guidance. Do
not believe there will be any runoff issues farther northwest
across CO/WY given lack of instability. While models differ farther
to the southeast, there are still non NAM solutions that have
potentially heavy rains as far northwest as northwest KS day 2,
supporting the west northwest expansion from the previous issuance.

...Southwest...
The closed low off the Southern CA coast day 1 is expected to move
little on day 2. The right entrance region of the jet streak to
the east of this closed low will push eastward from its day 1
position, but continue to support uvvs enhancement in the above
average PW axis, 1 to 3 standard deviations above the mean, that
will remain in place across Southern CA into the Southwest.
Additional scattered convection across these areas will support
localized heavy amounts and isolated runoff issues. The previous
marginal risk area was expanded westward into southeast CA to cover
the model qpf spread.

Oravec


Day 3
Valid 12Z Tue Sep 23 2025 - 12Z Wed Sep 24 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTHERN
MISSOURI, NORTHERN ARKANSAS, NORTHEAST OKLAHOMA AND SOUTHEAST KANSAS...

There continues to be model differences in the evolution of the mid
to upper level trof over the Central to Southern Plains toward the
Mid Mississippi Valley. The NAM continues to be an outlier in being
more amplified and faster to push the height falls downstream.
Despite the differences, models do show re-strengthening of the low
level southwesterly flow ahead of surface low pressure moving east
across Oklahoma into Arkansas. This will support potential for
organized convection, that likely forms late day 2 to the north of
this low across the Central Plains, continuing day 3 from southeast KS/northeast OK, across Southern MO and northern AR. Model
consensus is for the heaviest totals across these areas with
amounts of 2-4" possible. This heavy axis will possibly overlap
where heavy rains have fallen over the past 24 hours and where
additional heavy rains are possible during the day 1 period. There
were no major changes to the slight risk area from the previous
issuance. The marginal risk was extended farther westward into
northeast CO where several models show heavy rain potential day 3.
The eastern portion of the marginal risk was also extended into the
Upper OH Valley to cover the model qpf spread.

...Southern to Central California...
The nearly stationary closed low off the Southern CA coast day 2
will begin to slowly move back to the north on day 3 toward the
Central CA coast. This slow north movement will also allow for a
northward expansion of the anomalous PW values over Southern CA
into Central CA, with values as high as 3-4 standard deviations
above the mean. There are differences with qpf distributions given
differences with the northward push of the closed low. Not a lot
of confidence in any solution at this range, but continued
potential for locally heavy rains and isolated runoff issues,
especially over any burn scars. No changes made at the moment to
the previous broad marginal risk area over Southern to Central CA.

Oravec
$$
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FOUS30 KWBC 220821
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
421 AM EDT Mon Sep 22 2025

Day 1
Valid 12Z Mon Sep 22 2025 - 12Z Tue Sep 23 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTH
CENTRAL KANSAS INTO NORTH CENTRAL OKLAHOMA...

...Central to Southern Plains...
The latest model suite is in better agreement with the evolution
of the amplifying upper trof across the Northern to Central Rockies
day 1 and the downstream outbreak of organized convection along
and to the north of the path of the associated surface low moving
west to east from the TX Panhandle into western OK. A slight risk
area was added for the potential for organized convection along and
to the north of this low, across areas of south-central KS into
north-central OK where the low level southerly flow will be
strengthening and the corresponding 850-700 mb moisture flux
becoming anomalous, upwards to 2 to 3 standard deviations above
the mean by the end of the day 1 period. The neighborhood
probabilities are high in both the HREF and RRFS for 1 and 2"+
amounts across these areas. Additionally, both the HREF and RRFS
show a defined area of probabilities exceeding the 3 hourly FFG
values in the 0000-1200 UTC Tuesday time frame as the potentially
organized convection presses east southeastward.

...Mid to Lower Mississippi Valley into the Ohio Valley...
A broad marginal risk area was maintained in association with height
falls pushing east northeastward from the Mid Mississippi Valley
through the Ohio Valley. Well defined large scale lift in an axis
of above average PW values, 1 to 1.5+ standard deviations above the
mean, will support the likelihood of widespread moderate to heavy
precipitation in an axis from northern AR, far southeast MO, far
southeast IL, western to central KY, much of IN and OH. At the
moment the convection across these areas may be fairly progressive.
This and very low relative soil moistures, much of the area in
moderate to severe drought, will keep the risk level at marginal
for the time being. While the HREF and RRFS neighborhood
probabilities are fairly high for 1 and 2"+ amounts day 1, the HREF
and RRFS probabilities for 3 hour rainfall exceeding FFG values
remains very low, reflecting the antecedent very dry conditions.

...Southwest...
The closed low off the Southern CA coast is expected to move
little during the upcoming day 1 period. The right entrance region
of the jet streak to the east of this closed low will push
eastward, but continue to support uvvs enhancement in the above
average PW axis, 1 to 3 standard deviations above the mean, that
will remain in place across Southern CA into the Southwest.
Additional scattered convection across these areas will support
localized heavy amounts and isolated runoff issues. No changes were
made to the previous marginal risk area.

Oravec


Day 2
Valid 12Z Tue Sep 23 2025 - 12Z Wed Sep 24 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTHERN
MISSOURI, NORTHERN ARKANSAS, NORTHEAST OKLAHOMA AND SOUTHEAST KANSAS...

The strengthening 850-700 mb moisture flux late day 1 over the
Southern Plains will remain anomalous day 2 as surface low
pressure continues to push eastward from the Southern Plains toward
the Lower Mississippi Valley. 850-700 mb moisture flux anomalies
are forecast to remain in the 2 to 3+ standard deviation above the
mean level. This will support the likelihood for the continuation
of the day 1 organized convection over the Southern Plains, pushing
eastward into the Lower Arkansas Valley and toward the Mid to Lower
MS Valley. There are differences with the track of the primary
surface low, resulting in north to south spread with respect to
where the max precip axis will be. WPC is favoring the more
southern qpf axes solutions, with the max axis depicted from far
eastern OK, northern OK/far southern MO into western TN. This is a
slight southward trend from previous forecasts, reflecting a
southward trend in qpf guidance. Changes to the previous slight and
25% areas were to follow the slight southward qpf axis trend,
pushing them approximately 40-60 miles farther to the south.

...Coastal Central California...
There is good model agreement with the nearly stationary closed
low off the Southern CA coast day 1 beginning to slowly move back
to the north on day 2 toward the Central CA coast. This slow north
movement will also allow for a northward expansion of the
anomalous PW values over Southern CA into coastal Central CA, with
values as high as 3-4 standard deviations above the mean. With good
model agreement on the closed low track day 2, there is also good
agreement on potential for areal average moderate precip totals,
with potential for locally heavier amount along the Central CA
coast. Isolated runoff issues are possible, especially over any burn scars.

Oravec


Day 3
Valid 12Z Wed Sep 24 2025 - 12Z Thu Sep 25 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE
TENNESSEE AND OHIO VALLEY REGIONS...

The mid to upper level trof moving east from the Southern Plains
day 2 will amplify day 3 as it pushes into the Lower MS Valley.
Anomalous PW and 850-700 moisture flux values will stretch across a
large area from the Lower MS Valley, and into the TN & OH Valley,
Central Appalachians and the Mid-Atlantic. Model consensus is for a
broad region of moderate to heavy precip in this anomalous PW and
850-700 mb moisture flux axis. There is a typical amount of qpf
spread for a day 3 time period. WPC is leaning more toward the
multi model ensemble qpf mean axis/NBM axis to drive our qpf and
excessive rainfall axis. While a large portion of the day 3 QPF and
ERO axes are currently in moderate to severe drought, there may be
overlap in qpf areas from day 3 and day 1 over the TN and OH
Valley regions and overlap between the day 2 and day 3 qpf axes
across the Lower MS Valley into the TN Valley, which will likely
increase soil saturations and increase stream flows. The previous
slight risk area was trimmed on the western edge by approximately
75-100 miles across far southeast MO, southern IL and southern IN
to better fit the latest QPF.

...Central California...
The slow moving closed low approaching the central CA coast late
day 2 will continue to push slowly eastward day 3 and push inland
by early Thursday morning. Similar to the day 2 period, an axis of
anomalous PW values, 2 to 3 standard deviations above the mean,
will persist to the east northeast of the closed low across
Central CA. Scattered convection in this anomalous PW axis will
support locally heavy rains across Central CA and isolated runoff
issues, especially across burn scar regions. Only some small
changes made to the previous marginal risk area, trimming it
westward across western NV.

...Far southeast Arizona into New Mexico...
No changes of note made to the previous marginal risk area across
this region. Scattered convection possible, with localized heavy
rain and isolated runoff issues, especially in burn scar regions.

Oravec
$$
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FOUS30 KWBC 230825
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
425 AM EDT Tue Sep 23 2025

Day 1
Valid 12Z Tue Sep 23 2025 - 12Z Wed Sep 24 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTHERN
MISSOURI, FAR SOUTHEAST KANSAS, EASTERN OKLAHOMA, FAR NORTHEAST
TEXAS, ARKANSAS, WESTERN TENNESSEE, WESTERN KENTUCKY, AND SOUTHERN
ILLINOIS AND SOUTHERN INDIANA...

...Lower Arkansas Valley, Lower Mississippi Valley into the Lower
Ohio Valley...

The strengthening low level southerly flow/anomalous 850-700 mb
moisture flux that have supported organized convection over the
Central to Southern Plains early Tuesday will continue to support
the downstream push of this organized convection post 1200 UTC,
with these anomalous 850-700 mb moisture flux values of 2-3+
standard deviations above the mean moving from the eastern sections
of the Southern Plains into the Lower AR Valley, Lower MS, TN and
OH Valleys. There continues to be some north south spread in the
models with respect to the position of the max precip axis.
Generally, the non-CAMs are farther north and the CAMs farther
south. WPC continues to support the farther south qpf solutions,
with our day 1 risk areas drawn toward them. Overall, not a lot of
changes to the previous slight risk areas. We did extend the slight
risk farther east into the Lower OH Valley where there is expected
to be overlap of day 1 heavy precip with observed precip over the
past 24 hours. We also extended the slight risk area farther south
into northeast TX where several of the new 0000 UTC hi-res runs and subsequently the new HREF mean show heavy precip. Otherwise, the
slight and 25% areas fit well with where the HREF and RRFS
neighborhood probabilities are high day 1 for 2" and 3+ amounts.

...Coastal Central California...
There continues to be good model agreement with the nearly
stationary closed low off the Southern CA coast beginning to
slowly move back to the north on day 1 toward the Central CA
coast. This slow north movement will also allow for a northward
expansion of the anomalous PW values over Southern CA into coastal
Central CA, with values as high as 3-4 standard deviations above
the mean. With good model agreement on the closed low track day 1,
there is also good agreement on potential for areal average
moderate precip totals, with potential for locally heavier amount
along the Central CA coast. Isolated runoff issues are possible,
especially over any burn scars.

Oravec


Day 2
Valid 12Z Wed Sep 24 2025 - 12Z Thu Sep 25 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE
TENNESSEE AND OHIO VALLEY REGIONS...

Anomalous PW and 850-700 moisture flux values will stretch across a
large area from the Lower MS Valley, and into the TN & OH Valleys,
Central Appalachians and the Mid-Atlantic, ahead of the amplifying
longwave trof stretching from the Great Lakes, southward into the
Lower MS Valley. There still is a fair amount of qpf spread with
the max axis day 2. WPC is leaning more toward the multi model
ensemble qpf mean/NBM to drive our qpf and excessive rainfall
axes. This will support a widespread axis of moderate to heavy
precip amounts from eastern TX into the Lower MS Valley, TN and OH
Valleys. While a large portion of the day 2 QPF and ERO axes are
currently in moderate to severe drought, there may be overlap in
qpf areas from day 2 and what has fallen over the past 24 hours
from eastern TN into central to eastern KY, and the Upper OH Valley
region. The previous slight risk was narrowed to better fit this
potential overlap areas. The marginal risk was also trimmed
significantly from southern L.P. of MI, IL, southeast MO and AR to
better fit the latest qpf update.

...Central California...
The slow moving closed low approaching the central CA coast late
day 1 will continue to push slowly eastward day 2 and push inland
by early Thursday morning. Similar to the day 1 period, an axis of
anomalous PW values, 2 to 3 standard deviations above the mean,
will persist to the east northeast of the closed low across Central
CA. Scattered convection in this anomalous PW axis will support
locally heavy rains across Central CA and isolated runoff issues,
especially across burn scar regions.

...Far southeast Arizona into New Mexico...
No changes made to the previous marginal risk area across this
region. Scattered convection possible, with localized heavy rain
and isolated runoff issues, especially in burn scar regions.

Oravec


Day 3
Valid 12Z Thu Sep 25 2025 - 12Z Fri Sep 26 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTHEAST
ARIZONA AND FAR SOUTHWEST NEW MEXICO...

The slow moving closed low moving inland into Central CA day 2 will
drop back to the south southeast toward Southern CA day 3. This
system will continue to have an area of anomalous PW values in the
vicinity of the upper center across Central CA into the Great
Basin. This closed low will also begin to tap anomalous PW values
over northwestern Mexico, transporting them into southeast Arizona
day 3. Model consensus is for a max precip area over Southeast
Arizona and far southwest New Mexico. The previous slight risk
across this area was only modified slightly, expanding it slightly
to the north and east to cover the model max qpf spread. Only some
minor changes to the marginal risk to the northwest of this across
northern AZ, southern NV, far southwest UT and into the central
Sierra. Locally heavy rains and isolated runoff issues possible
across these areas, especially over burn scars.

...Southern to Central Appalachians...
There will continue to be a broad axis of above average PW values
pushing eastward day 3 ahead of the elongated upper trof
stretching from the Great Lakes into the OH and TN Valleys. There
is a lot of qpf differences in this high PW axis, leading to low
confidence in where to put risk areas. Much of the eastern U.S. is
in drought conditions with low relative soil moisture levels. One
exception is over portions of the Southern to Central Appalachians
from eastern TN/far western NC/far southwest VA and eastern WV.
Kept the day 3 marginal confined to these areas and removed the
broader marginal from the previous issuance that extended north and
east into the Mid-Atlantic and southwestward to the Gulf Coast.

Oravec
$$
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FOUS30 KWBC 240831
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
431 AM EDT Wed Sep 24 2025

Day 1
Valid 12Z Wed Sep 24 2025 - 12Z Thu Sep 25 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE
TENNESSEE AND OHIO VALLEY REGIONS...

...Southern Plains to the Central and Southern Appalachians...

Overall, no large-scale changes to the previous outlook areas,
maintaining a broad Marginal Risk that extends from portions of
central and southern Texas to the southern and central
Appalachians, with an embedded Slight Risk centered over parts of
the Ohio and Tennessee valleys.

Composite radar this morning shows widespread showers and storms
extending from the Ohio Valley back into the southern Plains. The
overnight CAMs indicate that ongoing storms along the far eastern Oklahoma-Texas border into southern Arkansas will remain organized
into the late morning as the drift slowly south, with training
storms likely to produce heavy amounts across portions of
northeastern Texas and northwestern Louisiana. Supported by
shortwave energy moving through the base of a broader-scale
positively-tilted upper trough and PWs at or above 2 inches, HREF
probabilities indicate locally heavy amounts exceeding 3 inches are
likely. However, dry soil conditions, reflected by high FFGs, are
expected to limit the threat for widespread flooding concerns.

As energy continues to move through the base of the upper trough,
an area of low pressure is expected to become better organized and
track northeast through the Ohio Valley beginning later this
afternoon and continuing into the overnight. Deep southwesterly
flow ahead of the wave will support increasing moisture, with PW
anomalies increasing to over 2 std dev above normal per the GFS.
Given the ongoing rains and relatively wetter soil conditions
(lower FFGs), a Slight Risk extending from far northern Alabama to
far southern Ohio and western West Virginia was maintained. HREF
probabilities indicate that amounts of 1-2 inches will be common,
with locally heavier amounts over 3 inches possible within the
Slight Risk area.

In the wake of the low, showers and storms producing heavier rates
are expected along the trailing front as it sinks south through
the lower Mississippi Valley and along the upper Texas coast back
into South Texas. Here too, the HREF is indicating locally heavy
amounts over 3 inches are likely. But similar to areas to the
north, higher FFGs suggest flooding issues will be mostly contained
to vulnerable areas, including urbanized centers.

...Northeast...

The general consensus of the CAMs shows an area of showers and
storms moving northeast well in advance of the system over the Ohio
Valley. Supported by deepening moisture along a slow-moving
boundary and increasing mid-to-upper level forcing, showers and
storms will advance northeast across Pennsylvania, with repeating
storms potentially resulting in locally heavy amounts from
northeastern Pennsylvania into the lower Hudson Valley/NYC area. A
A Marginal Risk was maintained for areas where the HREF shows
higher probabilities for amounts over 2 inches and where FFGs are
relatively lower.

...Southeastern Lower Michigan...

An upper low closing off this morning is expected to remain
centered over Lower Michigan into Thursday morning. Showers and
storms are likely to develop east of the center, with relatively
deeper moisture wrapping into the system raising the potential for
locally heavy rainfall rates. A small Marginal Risk was
introduced, highlighting the area where the HREF shows high
probabilities for accumulations exceeding 2 inches.

...Central California...

A slow-moving upper low currently offshore will drift north and
begin moving inland Thursday morning. With anomalous moisture
remaining in place (2.5-3 std dev above normal), locally heavy
amounts will remain possible. Reflecting the high HREF
probabilities for amounts over an inch, a Marginal Risk was
maintained along the central California Coast from the Monterey
Bay south and along the adjacent mountains.

Pereira


Day 2
Valid 12Z Thu Sep 25 2025 - 12Z Fri Sep 26 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTHEAST
ARIZONA AND FAR SOUTHWEST NEW MEXICO...

...Southwest to Sierra Nevada...

After moving inland early Thursday, the closed low over central
California is forecast to drop south into southern California by
early Friday. With ample moisture remaining in place (2-3 std
dev above normal) near and east of the upper center, locally heavy
amounts are possible from the Sierra Nevada east into southern
Nevada and southwestern Utah.

As the center drops south, increasing southerly flow east of the
low will draw deeper moisture up from Mexico, fueling widespread
shower and thunderstorm coverage, especially across southeastern
and central Arizona into southwestern New Mexico. A Slight Risk
was maintained across this area where PWs are forecast to increase
to 1-2 standard deviations above normal by the afternoon.

...Northeast...

Unsettled weather developing Day 1 is forecast to continue into
Thursday as showers and storms continue to develop ahead of the
system lifting out of the Ohio Valley into the Northeast.
Strengthening southwesterly flow along the Mid Atlantic coast into
the Northeast will support deepening moisture (PWs increasing to ~2
inches) and an increasing threat for heavy rainfall rates. A
Marginal Risk was maintained from northern New Jersey into southern
New England, where HREF probabilities indicate that localized
amounts over 3 inches are possible late Thursday morning into the
afternoon.

...Southern Appalachians...

The consensus of the latest guidance indicates that showers and
storms developing along and ahead of the cold front trailing the
low moving through the Northeast will be generally progressive.
With widespread heavy amounts not expected and FFGs high, the
previous Marginal Risk was removed from much of the Mid Atlantic.
However, some models do show the potential for training storms to
produce some localized heavy amounts (2+ inches) across parts of
the southern Appalachians, where a small Marginal Risk was
maintained.

Pereira


Day 3
Valid 12Z Fri Sep 26 2025 - 12Z Sat Sep 27 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTHEAST
ARIZONA AND SOUTHWEST NEW MEXICO...

...Southwest...

A second day of numerous showers and storms is expected across the
Southwest, especially for much of southeastern Arizona and parts of southwestern New Mexico. The upper low setting into southern
California the previous period is expected to move little this day,
remaining centered near the California/Mexico border. This will
help to maintain anomalous moisture across the region, fueling
widespread shower and thunderstorm coverage during the afternoon
and evening hours. A Slight Risk, with a footprint similar to the
Day 2 area, was maintained for Day 3 across parts of Arizona and
New Mexico.

...Southeast...

A boundary will remain in place across the Southeast as an upper
trough evolves into a closed low that is forecast to linger beyond
the period. Moisture and energy lifting ahead of the closing system
will support periods of shower and storms. While the guidance at
this point is not signaling any widespread heavy amounts, the
pattern does lend itself to at least the threat for locally heavy
amounts, which may raise at least isolated flooding concerns.

Pereira
$$
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FOUS30 KWBC 250744
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
344 AM EDT Thu Sep 25 2025

Day 1
Valid 12Z Thu Sep 25 2025 - 12Z Fri Sep 26 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTHEAST
ARIZONA AND FAR SOUTHWEST NEW MEXICO...

...Southwest to Sierra Nevada...
A cold low near the central California coast is forecast to drop
southeast into southern California by early Friday. With cold air
aloft overlying sufficient moisture near and east of the upper
center, locally heavy amounts are possible from the Sierra Nevada
east into southern Nevada and southwestern Utah.

Ahead of the system, increasing southerly flow will draw deeper
moisture into the Southwest from the Gulf of CA, fueling
widespread shower and thunderstorm coverage, especially across
southeastern and central Arizona into southwestern New Mexico. ML
CAPE should rise into the 1000-2000 J/kg range. A Slight Risk was
maintained across this area where cold air aloft interacts with
monsoon-like moisture, with precipitable water values as high as
1.25-1.5". Hourly rain amounts to 2" are possible where cells merge
and/or train.

...Northeast/Upper Ohio Valley...
Unsettled weather at the present time is forecast to continue into
Thursday as showers and storms stream east across the Upper Ohio
Valley, WV, and southwest PA ahead of a shortwave aloft and surface
frontal wave. While there may be a gap in heavy rainfall between
this region and points farther east, chose to connect the areas
and significantly broaden the inherited Marginal Risk.
Strengthening southwesterly flow along the Mid Atlantic coast into
the Northeast will support deepening moisture (PWs increasing to
~2") and ML CAPE surpasses 1000 J/kg. Hourly amounts to 2.5" are
possible in this region with local totals to 4", but coverage of
such amounts should be sparse enough for a Marginal Risk to still apply.

...Southern Appalachians into parts of the Gulf Coast...
Amplifying mid-upper trough digging into the northwest and north-
central Gulf will slow the south and east progression of the
surface cold front and pre-frontal buoyant airmass. ML CAPE values
should rise to 1000 J/kg or so across the southernmost
Appalachians while areas of the Gulf Coast see 2000-3000 J/kg of ML
CAPE. With precipitable water values at or above 2", hourly rain
amounts to 2.5" with local totals to 4" are possible wherever short
periods of training or cell mergers are able to occur. Activity
currently across South TX should survive past 12z, so looped the
Marginal Risk to encompass this area. At the present time, any
flash flood issues are expected to be isolated to widely scattered.

Roth


Day 2
Valid 12Z Fri Sep 26 2025 - 12Z Sat Sep 27 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTHEAST
ARIZONA AND SOUTHWEST NEW MEXICO...

...Southwest...
Numerous showers and thunderstorms are expected across the
Southwest, especially for much of southeastern Arizona and parts of southwestern New Mexico. An upper low should slow to a crawl
across southeast California. Precipitable water values should
remain as high as 1.25-1.5" in spots, but the guidance shows more
potential on the ML CAPE front when compared to Thursday, with
values of 2000-3000 J/kg possible as available moisture interacts
with the cold pool aloft. Widespread shower and thunderstorm
coverage is expected, particularly during the afternoon and evening
hours. A Slight Risk, with a footprint similar to the Day 2 area,
was maintained for Day 3 across parts of Arizona and New Mexico,
but it could be higher end Slight Risk. Hourly rain amounts to 2"
are possible where cells merge and/or train.

...Southeast...
A boundary will remain in place as a cold low forms near the base
of an upper level trough, a feature that lingers for a while near
the Southern Appalachians. Moisture and instability lifting ahead
of the closing system will support periods of showers and storms.
Precipitable water values of up to 2" with ML CAPE to 1000 J/kg
across the Piedmont and 2000-3000 J/kg in coastal areas are
expected, which could yield hourly rain amounts to 2.5" and local
totals to 4".

Roth


Day 3
Valid 12Z Sat Sep 27 2025 - 12Z Sun Sep 28 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF FAR
WEST TEXAS & NEW MEXICO...

Southwest/Southern Rockies...
An upper low remains fixed across the Lower Colorado River while
Gulf Moisture streams into the TX Big Bend and New Mexico, moving
up the Rio Grande. Precipitable water values of 1.25-1.5" are
forecast, which when combined with up to 1000 J/kg of ML CAPE could
yield hourly amounts to 2.5" and local totals to 4" where cells
train and/or merge. Believe the risk level from continuity (Slight)
conveys the risk appropriately at this time for portions of far
west TX and NM. Closer to the upper level center across the
Southwest, slow-moving convection is possible under the cold pool
aloft. Based on the decline of the 1000-500 hPa thickness across UT
towards 5670 meters, limited the northern extent of the Marginal
Risk to southern UT which is about the northern extent of the 0.75" precipitable water value, which was coordinated with the SLC/Salt
Lake City forecast office.

Carolinas/Southern Mid-Atlantic States...
Divergence aloft around the eastern periphery of a cold low near
the Southern Appalachians maintains precipitable water values of
2"+ near the coast, which should also see the greatest instability,
up to 1000 J/kg. The guidance shows a bit of dispersion here in placement/northeast movement of the heavy rain area with the GFS
and NAM in their usual camps (fast and slow, respectively). Hourly
rain amounts to 2.5" and local totals to 4" are expected, similar
to previous days. Forecast uncertainty, as much as anything else,
maintained the risk level as a Marginal. Should the guidance
converge, areas of risk overlap between Friday and Saturday across
portions of the coastal plain of the Carolinas could see an upgrade
to a Slight Risk at some point as we get closer to Saturday.

Roth
$$
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FOUS30 KWBC 260808
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
408 AM EDT Fri Sep 26 2025

Day 1
Valid 12Z Fri Sep 26 2025 - 12Z Sat Sep 27 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE SOUTHWEST & IN THE VICINITY OF THE CAROLINAS...

...Southwest...
Numerous showers and thunderstorms are expected across the
Southwest, especially for much of southeastern Arizona and parts of southwestern New Mexico, which should occur primarily during the
afternoon and evening hours. An upper low should slow to a crawl
across southeast California. Precipitable water values should
remain as high as 1.25-1.5" in spots. ML CAPE values of 2000-3000
J/kg are possible as available moisture interacts with the cold
pool aloft. A Slight Risk was maintained across parts of Arizona
and New Mexico, but it could be higher end Slight Risk. Hourly rain
amounts to 2" with local totals to 4" are possible where cells
merge and/or train.


...Southeast...
A boundary will remain in place as a cold low forms near the base
of an upper level trough, a feature that lingers for a while near
the Southern Appalachians. Farther inland across the Piedmont, some
degree of upslope flow should bring some of the higher moisture
back in from the southeast. Moisture and instability lifting ahead
of the closing system will support periods of showers and storms.
Precipitable water values of up to 2" with MU CAPE of 1000+ J/kg
across the Piedmont and 2000-3000 J/kg in coastal areas are
expected, which could yield hourly rain amounts to 2.5" and local
totals to 4". As the 00z HREF and 18z REFS had their strongest
signal for 3"+ and 5"+ across far southwest VA and the western
Carolinas, a Slight Risk was added in this update, which was
coordinated with the local offices. For the time being, a Slight
Risk was left out across the coastal plain of the Carolinas as
recent dryness could make a higher incidence of flash flooding
harder to come by, which was coordinated with the coastal Carolina
offices.

Roth


Day 2
Valid 12Z Sat Sep 27 2025 - 12Z Sun Sep 28 2025


...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF FAR
WEST TEXAS & NEW MEXICO...

...Southwest/Southern Rockies...
An upper low remains fixed across the Lower Colorado River while
Gulf Moisture streams into the TX Big Bend and New Mexico, moving
up the Rio Grande. Precipitable water values of 1.25-1.5" are
forecast, which when combined with 1000+ J/kg of ML CAPE could
yield hourly amounts to 2.5" and local totals to 4" where cells
train and/or merge. Believe the risk level from continuity (Slight)
conveys the risk appropriately at this time for portions of far
west TX and NM. Closer to the upper level center across the
Southwest, slow-moving convection is possible under the cold pool
aloft, with ML CAPE of 1000-2000 J/kg of instability and
precipitable water values in the Lower Desert of 1-1.25" expected.
Based on the decline of the 1000-500 hPa thickness across UT
towards 5670 meters, limited the northern extent of the Marginal
Risk to southern UT which is about the northern extent of the 0.75" precipitable water value.


...Carolinas/Southern Mid-Atlantic States...
Divergence aloft around the eastern periphery of a cold low near
the Southern Appalachians and what is now a tropical disturbance
moving through the Bahamas as a possible tropical cyclone on
Saturday team up to maintain precipitable water values of up to
2.25" across the coastal plain, which should also see the greatest
instability, 1000-2000 J/kg. The Piedmont should see times when the
MU CAPE rises above 500 J/kg. This is a PRE-like set up for the
region, so the heavy rainfall potential has a higher upside than
usual. There has been some convergence in the model guidance QPF-
wise, and both the 00z HREF and 18z REFS had a cohesive and
agreeable enough heavy rain threat of 3"+ for a new Slight Risk
area from roughly Richmond VA south on both sides of the fall line
into eastern SC. Hourly rain amounts to 3" and local totals to 6"
are possible, which is potentially problematic anywhere within the
Slight Risk area. A higher risk level can't be ruled out in future
updates.

Roth



Day 3
Valid 12Z Sun Sep 28 2025 - 12Z Mon Sep 29 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF FAR
WEST TEXAS, NEW MEXICO, & THE CAROLINAS...

Southwest/Southern Rockies...
The combination of an upper low moving to near the Four Corners, a
kicker upper level trough moving into CA, and moisture feed from
the Gulf into NM persist into Sunday. Precipitable water values
remain above 1" locally in the Desert Southwest and 1-1.25" in the
Southern High Plains. Pockets of 1000+ J/kg of ML/MU CAPE are
forecast to develop and/or persist. A Slight Risk still appears
reasonable across portions of far west TX and NM, with a broader
Marginal Risk surrounding that. The guidance appears to be trending
somewhat drier across the Great Basin, so limited the northern
extent of the Marginal Risk area when compared to continuity.


Florida northward into the Southern Mid-Atlantic States...
A system now considered a tropical disturbance over Hispaniola
should lie somewhere north of the Bahamas and east of Florida as a
possible tropical or hybrid cyclone on Sunday. The upper level
environment doesn't look kind for whatever emerges, and there are
two scenarios -- a more convective system that remains offshore
during the medium range period or a more sheared system that
attempts to occlude when it approaches landfall early next week.
The guidance is not ideal in differentiating which is correct
during these scenarios, historically.

Regardless, moisture will not be a problem regionally --
precipitable water values locally 2"+. Coastal areas will see
1000+ J/kg of ML CAPE while 250+ J/kg of MU CAPE invades portions
of VA. The guidance has slowed down the approach of the tropical
low since yesterday, but the other players in the flow pattern
remain -- the upper low near the southern Appalachians/southern
Cumberland Plateau and the front near the East Coast. A PRE- like
set up appears to be in the cards, with moisture streaming into the
front from the south. The best signal for heavy rainfall on Sunday
into early Monday appears to be in the vicinity of Myrtle Beach,
and considering previous days of rain, thought a new Slight Risk in
that area would be prudent. In theory, hourly rain amounts to 3"
should be possible, which would be most problematic should
thunderstorms merge or train.

Roth
$$
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FOUS30 KWBC 270831
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
431 AM EDT Sat Sep 27 2025

Day 1
Valid 12Z Sat Sep 27 2025 - 12Z Sun Sep 28 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE SOUTHWEST AND MID-ATLANTIC...

Southwest/Southern Rockies/High Plains

A closed upper low over the Southwest will generate scattered
thunderstorm activity across the region and into parts of the
Southern High Plains/Rockies beginning this afternoon. Anomalous
moisture (1in+ PWAT/2-3 StD) within a bouyant environment 1000+
MUCAPE should yield modest rain rates of over an inch/hr,
especially over favorable upslope terrain. Burn Scars and slot
canyons will be among the most susceptible to flash flooding.

Mid-Atlantic/Southeast

An upper trough will continue supplying ample moisture (1.5-2in+
PWAT) and sufficient instability (500 J/Kg+) to the Mid-
Atlantic/Southeast Coastline today. Storms should develop within
the warm sector of a stationary front draped across the Southern
Appalachians and Mid-Atlantic Coast. The heaviest rainfall (1-2
in/hr rates) should focus around the aforementioned front where
favorable right entrance region dynamics will likely develop and
prolong storms during peak heating hours.


Kebede

Day 2
Valid 12Z Sun Sep 28 2025 - 12Z Mon Sep 29 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
FAR WEST TEXAS, NEW MEXICO AND SOUTHWESTERN COLORADO...

Southwest/Four Corners/Southern High Plains/Rockies

The upper low in the Southwest is expected to open as it lifts
into the Rockies on Sunday. The threat for excessive rainfall thus
expands a bit around the trough as the fetch of moisture from the
previous day rotates around the low and into parts of the Great
Basin and Four Corners. Some elevated instability 500 J/Kg+ MUCAPE
could generate 0.5-1.5 in/hr rates, especially over parts of New
Mexico, where a slight risk is in effect. Antecedent rainfall from
Saturday should lower FFGs, making soils more vulnerable to flash
flooding. Slot canyons, dry washes and upslope areas will likely be
the most susceptible to runoff.

Southeast

Guidance continues to trend farther away from the Southeast Coast
with the axis of substantial QPF associated with a tropical
cyclone moving through the Bahamas at the beginning of the day 2
period (Sunday morning). Given the uncertainty of the system's
track, it's difficult to say with any confidence if/where the most
impactful rainfall will occur, thus a broad marginal is in place
from the Outer Banks down to Miami for now.


Kebede

Day 3
Valid 12Z Mon Sep 29 2025 - 12Z Tue Sep 30 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE SOUTHEAST AND MID-ATLANTIC...

Southeast/Mid-Atlantic

Tropical moisture arrives along the Southeast/Mid-Atlantic Coast
on Monday ahead of the associated cyclone, which is currently
forecast to be east of Georgia by Tuesday morning. Current
deterministic guidance has between 2-4 inches of rainfall occurring
along the Carolina Coast with isolated higher amounts. Models are
trending away from the coast with the cyclone's track, which is
reflected in a decreasing QPF trend with this cycle as well.

Northern California/Southwest Oregon

A deep East Pacific trough will bring broad diffluent flow aloft
over the Northwest Coast beginning Monday morning. Scattered
showers and thunderstorms may develop along the leading edge of a
surface front, where the presence of weak instability (350 J/Kg
MUCAPE) and modest moisture (~1 in. PWAT) could produce localized
flash flooding along the northern California/southwest Oregon
Coasts and inland into the Southern Cascades and northern Sierra.

Kebede
$$
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FOUS30 KWBC 280829
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
429 AM EDT Sun Sep 28 2025

Day 1
Valid 01Z Sun Sep 28 2025 - 12Z Sun Sep 28 2025

...THERE'S A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS MUCH OF NEW
MEXICO AND PORTIONS OF FAR WESTERN TEXAS/SOUTHERN COLORADO...

...Four Corners/Southwest...
An upper trough centered over the Southwest will continue
directing mid-level vortices northward through the Four Corners
region today. Moisture from Tropical Cyclone Narda in the East
Pacific will continue surging north into the Four Corners, where
scattered showers and thunderstorms are likely to proliferate throughout
the day. PWATs between 1-1.5 inches within the right entrance
region of the upper jet and modest instability around 500-1000+
J/Kg (MLCAPE) could yield rain rates between 0.5-1 in./hr.,
especially where the slight risk is currently drawn. Burn scars,
scars slot canyons and upslope areas within the risk areas are
especially vulnerable to flash flooding.

HREF's neighborhood exceedance probabilities of 2 in. in 24 hours
are between 25-50% while EAS probabilities of exceeding 0.5 in.
hover around 20-40% within the depicted slight risk area.


...Southeast...
An upper trough will pivot eastward over the Southeast while
moisture from T.C. Nine continues surging northward toward the
Southeast Coast. Current guidance keeps the axis of heaviest QPF
offshore, but enough moisture may propagate far enough north and
west to interact with a surface front draped along the coast and
produce localized excessive rainfall. HREF EAS exceedance
probabilities of 1 inch in 24 hours are between 5-15% along much
of the Carolina Coast today, which supports the marginal risk area
depicted.

Kebede

Day 2
Valid 12Z Sun Sep 28 2025 - 12Z Mon Sep 29 2025

...THERE'S A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
CAROLINA COAST...

...Southeast...
Guidance continue to depict T.C. Nine propagating north toward the
Southeast Coast on Monday, while a surface front draped along the
coast acts as the focus for heavy rainfall. QPF has trended
downward given slowing trends in the track of T.C. Nine on Monday.
The GFS suite in particular diverges most from the Canadian and
Euro suites when depicting the system's slower forward motion.
Despite this, enough moisture should work its way into the coast
and interact with the surface front to generate scattered thunderstorms. There'll be enough moisture (1.5-2.5in PWATs) and instability
(1000+ J/KG MUCAPE) present to support rainfall rates in excess of
1 in./hr..

...Northern California/Great Basin/Southern Cascades...
An upper low centered over the East Pacific will send mid-level
vortices into the West Coast on Monday. Pacific moisture may
collide with the remnant tropical moisture from Narda to produce
heavy rainfall from northern California into the Great Basin.
Synoptic forcing provided by a strong surface cold front should
focus PWATs in the range of 0.75-1.25 in. to produce quarter inch
rain rates along the immediate coast. More robust instability over
the Great Basin should yield higher rain rates between 0.5-1
in./hr. in some areas. Upslope enhancement may generate higher
totals in parts of the terrain.

Kebede

Day 3
Valid 12Z Mon Sep 29 2025 - 12Z Tue Sep 30 2025

...THERE'S A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
CAROLINA COAST...

...Southeast...
The inherited marginal and slight risk areas along the Southeast
Coast were downsized based on trends in the guidance suggesting
T.C. Nine's hard turn out to sea on Tuesday. Despite the resulting
smaller QPF footprint than previous cycles, the flash flood risk
remains. Instability will be negligible (less than 500 J/Kg
MUCAPE), which supports the possibility that the flood threat will be
due to runoff over saturated soils from Sunday and Monday's
rainfall. Exceedance probabilities of over 2 inches is over 10% in
the 00z ECENS/CMCE, while below 10% in the GEFS along the
immediate Carolina Coast.

Kebede
$$
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FOUS30 KWBC 290830
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
430 AM EDT Mon Sep 29 2025

Day 1
Valid 01Z Mon Sep 29 2025 - 12Z Mon Sep 29 2025

...THERE ARE MARGINAL RISKS OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA, SOUTHWESTERN OREGON, THE GREAT BASIN, SOUTH-
CENTRAL NEW MEXICO AND THE SOUTHEAST...

...Carolinas...
Moisture from tropical storm Imelda is expected to continue
streaming into the Southeast Coast today. A surface front draped
off the coast should provide forcing for thunderstorm development
beginning this morning. Convective bands may work their way into a
moisture rich environment in the Carolinas, where PWATs will be
between 1.5-2.25in.. MUCAPE between 250-500 J/Kg will spread
inland throughout the day, but the greatest convective potential
will be within the bands that propagate inland through North
Carolina this morning and afternoon. Neighborhood probabilities of
exceeding 2 inches of rainfall in 24 hours are between 15-30% over
parts of western and central North Carolina today.

Despite the presence of deep tropical moisture, much of the
convection and heaviest rainfall associated with Imelda should stay
offshore closer to Imelda and the draped front.

...Northern California/Great Basin...
A deep upper low centered over the Gulf of Alaska will send waves
of low pressure into the West Coast over the next couple of days.
A strong cold front may bring heavy rainfall to portions of
Northern California up into southern Oregon and the Great Basin
today. A weak instability gradient will develop ahead of the front
this afternoon and during peak heating. The 00z HREF suggest up to
0.25in./hr. rates across the coastal ranges, southern Cascades and
northern Sierra, with potential for upslope enhancement across
windward facing slopes.

EAS 24 hour 1 inch exceedance probabilities are over 45% along the
coast and southern Cascades, while a more modest 5-15% chance
remains over the Great Basin. There's a steep drop off in
probabilities once you get into the 2 inch exceedance range.

...South-central New Mexico...
There continues to be a signal for heavy rainfall over much of the
Sacramento Mountains, where instability (500-1000 J/Kg MLCAPE)
could support thunderstorm development and propagation into the
mountains early this evening. Much of the state has already
received over a half inch of rainfall in the past 24 hours with
pockets of 2 inch amounts present including within the Sacramento
Mountains. This may contribute to susceptibility of soils to runoff
from additional rain. Burn Scars such as the Ft. Stanton Piles
prescribed burn area are especially susceptible to flash flooding.

Kebede


Day 2
Valid 12Z Mon Sep 29 2025 - 12Z Tue Sep 30 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE GREAT BASIN AND NORTHERN ROCKIES...

The marginal risk area inherited from the previous cycle was mostly
maintained with an expansion south into central Utah due to trends
in the guidance. The cold front responsible for heavy rainfall
potential in northern California on Monday will propagate through
the Great Basin and Northern Rockies on Tuesday, focusing
additional instability and moisture along its convergence zone.
Ensemble exceedance probabilities of 0.5 inches in 24 hours are
between 5-25% over parts of northeastern Nevada, northern Utah,
southeastern Idaho and western Wyoming. The progressive nature of
the front should mitigate flash flooding concerns.

Kebede


Day 3
Valid 12Z Tue Sep 30 2025 - 12Z Wed Oct 01 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OLYMPIC PENINSULA...

A shortwave propagating through the southern periphery of the Gulf
of Alaska low will phase with it and move just off of the British
Columbia Coast by Wednesday. This new system will send a cold
front into the Pacific Northwest. The proximity of the upper low
and associated vorticity lobes should destabilize the environment
(100-300 J/Kg MUCAPE) enough to support isolated thunderstorm
activity. Favorable RER dynamics and mid-level moisture
advection should support efficient rain rates especially over the
Olympic Mountains. ECENS 24 hour exceedance probabilities of 2
inches is between 20-40% for much of the area.

Kebede
$$
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FOUS30 KWBC 300816
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 AM EDT Tue Sep 30 2025

Day 1
Valid 01Z Tue Sep 30 2025 - 12Z Tue Sep 30 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OLYMPIC MOUNTAINS, GREAT BASIN AND NORTHERN ROCKIES...

...Great Basin/Northern Rockies...
A deep upper low off the British Columbia Coast will send
shortwave energy through the Northwest today. A progressive cold
front will focus showers and thunderstorms over portions of the
Great Basin from northeast Nevada to western Montana/northern
Idaho. MUCAPE values between 100-500J/Kg and PWATs of 0.5-1in.
could produce excessive rainfall through this afternoon. This will
be especially true over portions of eastern Nevada into northern
Utah where 24 hour 1 inch exceedance probabilities are between 20-45%.

...Olympics...
The occluded parent low will direct anomalous Pacific moisture at
the Olympic coast beginning this afternoon. Some weak instability
(<200J/Kg MUCAPE) and PWAT's around 1 inch could produce some cells
capable of generating efficient rain rates, especially within the
windward side of the Olympics. IVT values between 500-700Kg/ms
support the excessive rainfall threat with isolated instances of
flash flooding.

Kebede


Day 2
Valid 12Z Tue Sep 30 2025 - 12Z Wed Oct 01 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OLYMPIC MOUNTAINS...

The excessive rainfall threat over the Olympics bleeds into
Wednesday as the upper low arrives off the coast of the Pacific
Northwest. A jetstreak aloft with MUCAPE around 150J/Kg Wednesday
morning could support some weak convection into the Olympics.
Unlike on day 1, maximum IVT values will remain offshore with 1
inch PWATs arriving early Thursday morning. Canadian and Euro
ensemble 2 inch exceedance probabilities are between 40-60% while
the GEFS 1 inch probabilities are around an inch.

Kebede


Day 3
Valid 12Z Wed Oct 01 2025 - 12Z Thu Oct 02 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE GREAT BASIN AND EASTERN FLORIDA...

...Great Basin...
The upper low is expected to dig into the West Coast on Thursday
directing diffluent flow and left exit region jet dynamics into the
Great Basin. Weak instability (100-200J/Kg MUCAPE) along a
developing cold front could generate thunderstorms capable of
producing some isolated flash flooding, especially over parts of
the Great Basin that received rainfall on Tuesday.

...Eastern Florida...
An upper trough in the Southeast will direct embedded vorticity
into the Florida peninsula on Thursday. An upper ridge centered
over the West Atlantic will advect tropical moisture (PWATs
between 1.5-2in.) into eastern Florida, where it'll interact with
an inverted trough along the coast. Multiple rounds of short fused
convection will proliferate from the central Gulf across the
Florida Peninsula throughout the day with onshore flow into eastern
Florida producing isolated instances of flash flooding.
Probabilities of 24 hour qpf exceeding 1 inch is between 15-30%
across eastern Florida. Urban areas are especially susceptible to
flash flooding.

Kebede
$$
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FOUS30 KWBC 010833
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
433 AM EDT Wed Oct 1 2025

Day 1
Valid 12Z Wed Oct 01 2025 - 12Z Thu Oct 02 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OLYMPIC PENINSULA AND EASTERN FLORIDA...

...Olympic Peninsula...
A deep upper low centered off of the British Columbia Coast will
direct embedded ripples of vorticity into the Pacific Northwest
today. A strong 60-100 kts RER jet with associated 100-200 J/Kg
MUCAPE and 200-400 Kg/ms IVT out of the southwest should be enough
to generate scattered thunderstorm activity across the region
today. These favorable dynamics paired with PWATs between 0.65-0.90
should produce efficient rain rates throughout the day, especially
along the windward side of the Olympics, where upslope enhancement
may occur.

...Eastern Florida...
A positively tilted trough will swing through the Southeast today.
CAA over warm Gulf/Atlantic waters should generate convection along
a surface convergence zone over the Florida Coast today. MUCAPE
between 500-1000 J/Kg within a moist environment (1.75-2.25 in.
PWATs) should produce scattered thunderstorms with efficient rain
rates. Moist easterly flow over the inverted coastal surface trough
may generate some backbuilding storms this afternoon/evening. HREF
5" neighborhood exceedance probabilities are between 20-30% across
the entire risk area, so there's potential for overperformance of
rainfall. Urban areas are of particular concern to flash flooding.

Kebede


Day 2
Valid 12Z Thu Oct 02 2025 - 12Z Fri Oct 03 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OLYMPIC PENINSULA, THE SIERRA, THE GREAT BASIN AND EASTERN FLORIDA...

...Olympic Mountains...
The excessive rainfall threat spills over into Thursday across the
Olympics as the upper low begins to dig down into the West Coast.
100-200 J/Kg MUCAPE and 0.75-1" PWATs should sustain the potential
for excessive rainfall, particularly earlier on in the period
(12-18z) before the trough pushes farther east into the interior
and high pressure builds over the Olympic Peninsula. CMCE 1"
exceedance probabilities are around 15-35% within the marginal risk area.

...Great Basin/Sierra...
Strong diffluence associated with the digging upper trough will
spread throughout the interior West on Thursday. An 80-100 kts RER
jet with a 100 J/Kg MUCAPE should support convection with PWATs
between 0.75-1", which will be 3-4 stndv above average. This will
provide enough moisture to produce high enough rain rates to
overtake flash flood guidance, which is below 1".

...Eastern Florida...
Shortwave vortices within a mean upper trough will propagate south
through the Florida Peninsula on Thursday. Sufficient instability
(500-1000 J/Kg MUCAPE) and moisture (2"+ PWATs) associated with
Imelda may produce excessive rainfall along the immediate coast
early on in the day. The latest qpf trend is decreasing, partly
because the heavy rainfall threat is split between two days (00z
Wednesday--15z Thursday), but urban areas continue to be
susceptible to runoff.

Kebede


Day 3
Valid 12Z Fri Oct 03 2025 - 12Z Sat Oct 04 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
EASTERN FLORIDA...

...Eastern Florida...
Continued troughing in the Southeast will promote more unsettled
weather across Florida on Friday. Easterly flow will continue
advecting rich tropical moisture (2-2.25" PWATs) from Imelda into
the Peninsula with plenty of instability (500-1000 J/Kg MUCAPE) to
generate scattered thunderstorms. 2" ensemble exceedance
probabilities are between 5-15%, which supports the inherited
marginal risk area. Again, the greatest threat for flash flooding
is in urbanized areas.

Kebede
$$
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FOUS30 KWBC 020828
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
428 AM EDT Thu Oct 2 2025

Day 1
Valid 12Z Thu Oct 02 2025 - 12Z Fri Oct 03 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SIERRA, GREAT BASIN AND EASTERN FLORIDA...

...Sierra/Great Basin...
An upper low will dig into the West Coast while sending streams of
vorticity into the Sierra Nevada, Great Basin and Northern
Rockies. Diffluence will spread across the aforementioned areas
throughout the day on Friday. At the surface, a low pressure system
will propagate across the interior West, while anomalous moisture
(3-4 stndv PWATs) streams in behind the preceding cold front.
Scattered to isolated thunderstorms may develop and produce
isolated instances of excessive rainfall and flash flooding.

Upslope enhancement across the Sierra could produce heavier
rainfall totals than what are currently forecast. EAS probabilities
of 24 hour qpf exceeding 1 inch are over 40% in the Sierra and
between 15-40% in the Great Basin. Therefore, burn scars over
central and southern Idaho are at risk of flash flooding today.

...Eastern Florida...
Moist easterly flow into a surface front oriented north-south will
produce scattered convection across Florida today. The surface
boundary draped along the eastern coast will focus PWATs of around
2" in that area where MUCAPE between 500-1000 J/Kg will also likely
produce high rain rates. Neighborhood probabilities of exceeding
5" in 24 hours are between 40-90% from near Miami metro up through
Melbourne and Orlando.

Kebede


Day 2
Valid 12Z Fri Oct 03 2025 - 12Z Sat Oct 04 2025

...THERE'S A MARGINAL RISK FOR PORTIONS OF THE GREAT BASIN AND
EASTERN FLORIDA...

...Great Basin...
The upper trough propagates through the Great Basin and begins
lifting north on Friday. The excessive rainfall threat bleeds into
Friday from Thursday as thunderstorms weaken and spread from the
Great Basin into the Northern Rockies by Friday afternoon. Instability
and moisture will be relatively modest (100-200 J/Kg MUCAPE)
(0.5-0.9"). Ensemble exceedance probabilities of 1" are between
10-20% over northern Nevada with 2 day totals potentially eclipsing
2" in some places.

...Eastern Florida...
Moisture advection into Florida increases on Friday as a mid-level
circulation embedded within a broader upper ridge continues to
direct moisture and instability into the state's east coast.
Another inverted surface trough may develop along the state's east
coast and focus convection along the convergence zone. Ensemble
exceedance probabilities of 2" are between 5-15% along the
immediate coast, while first guess fields support the marginal with
5% flash flood probabilities.

Kebede


Day 3
Valid 12Z Sat Oct 04 2025 - 12Z Sun Oct 05 2025

...THERE'S A MARGINAL RISK FOR PORTIONS OF SOUTHEAST LOUISIANA AND
EASTERN FLORIDA INTO FAR SOUTHEASTERN GEORGIA...

...Central Gulf Coast...
Mid-level vorticity swirling over the Central Gulf Coast will
generate instability and pull an increasing amount of Gulf
moisture into the region on Saturday. Convection should fire along
a coastal convergence zone that develops and diurnal heating should
enhance afternoon/evening storms along that boundary. PWATs will
likely be over 2" with MUCAPE between 500-750 J/Kg. Ensemble exceedance probabilities of 2" are between 15-30% for much of southeast Louisiana.

...Eastern Florida/Southeastern Georgia...
Tropical moisture associated with Imelda will continue flowing into
Florida due to and upper ridge over the East Coast and embedded
troughing over Florida and the Gulf. A modest instability plume
should flow up the Florida Peninsula into far southeastern Georgia
where PWAT's of over 2" and an inverted surface trough could
combine to produce thunderstorms capable of generating 0.75-1"/hr
rain rates. Ensemble exceedance probabilities of 2" are between
5-15% along Florida's east coast into southeastern Georgia.


Kebede
$$
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FOUS30 KWBC 030743
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
343 AM EDT Fri Oct 3 2025

Day 1
Valid 12Z Fri Oct 03 2025 - 12Z Sat Oct 04 2025

...THERE'S A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
FLORIDA'S EAST COAST...

...Florida's East Coast...

A closed mid-level disturbance will drift westward across the
Florida Peninsula and into the Gulf of Mexico today. This system
will bring tropical moisture from Imelda and Humberto with it. An
inverted trough oriented along the Florida coast will interact with
the moisture advecting into the region and force scattered
thunderstorm activity throughout the day. Modest instability
between 500-1000 J/Kg MUCAPE could produce quarter to half inch
rates over the slight risk area. Parts of central and southern
Florida that have received between 2-4 (isolated 5) inches of rain
in the past 24 hours will be especially susceptible to runoff from
today's storms. Neighborhood exceedance probabilities of 5 inches
are between 20-40% across Florida's east coast today.

...Great Basin...

Additional rainfall is forecast to occur beneath the upper low,
which will continue propagating through the interior West today.
Recent heavy rainfall over portions of the Great Basin will likely
prime surfaces for runoff from additional precipitation. Burn
scars in central and southern Idaho continue to be of concern from
today's storms, the bulk of which should occur this morning into
afternoon before the upper low moves directly over the Great Basin
and instability weakens. HREF EAS exceedance probabilities of over
1 inch are between 15-35% over northern/central Nevada where PWATs
will be between 2-3 standard deviations above normal.

Kebede


Day 2
Valid 12Z Sat Oct 04 2025 - 12Z Sun Oct 05 2025

...THERE'S A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
FLORIDA'S EAST COAST...

...Florida's East Coast...

Thunderstorms are expected to continue to develop along the
inverted trough axis oriented north-south along Florida's east
coast on Saturday. Moisture will lift north along with the mid-
level disturbance. The inherited slight and marginal risk areas
were maintained due to a mostly consistent signal for excessive
rainfall over the east central coast. Ensemble exceedance
probabilities of 2 inches are between 5-10% across the marginal
risk area. 48 hour totals between 3-5 inches (local 6") will likely
make overcoming flash flood guidance a bit easier.

...Central Gulf Coast...

The same moisture regime impacting the Florida peninsula will focus
over the central Gulf Coast this weekend. Mid-level vorticity will
lift into the area on Saturday, providing forcing for convection
along the immediate Louisiana/Mississippi coast. Anywhere between
4-6 inches of rain may occur over far southeastern Louisiana
through Saturday night. Despite 2" ensemble exceedance
probabilities being relatively low (5-10%), the multi day nature
of the rainfall could still produce isolated instances of flash flooding.

Kebede


Day 3
Valid 12Z Sun Oct 05 2025 - 12Z Mon Oct 06 2025

...THERE'S A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE CENTRAL GULF COAST AND THE SOUTHEAST COAST...

...Central Gulf Coast...

The mid-level disturbance continues propagating westward toward the
positively tilted upper trough centered over the West on Sunday.
Thus, the heavy rainfall threat will likely bleed over from
Saturday evening into Sunday morning for portions of the Central
Gulf Coast, before dissipating beneath diminished support aloft.
PWATs of 2-2.5" and instability between 500-1000 J/Kg MUCAPE could
churn out rain rates between 1-1.5"/hr Saturday morning into
afternoon. Ensemble exceedance probabilities of 2 inches are
between 5-15% along the far southeastern Louisiana to Florida
panhandle corridor, which supports the marginal risk area in place.

...Southeast Coast...

Inverted troughing continues along the Florida/Southeast Coast
through the latter part of this weekend. Anomalous moisture (2-3
stndv) will continue interacting with the surface boundary to
generate scattered to isolated thunderstorms across the
Florida/Georgia coast. Rainfall totals of 1-3" are likely along
the Florida/Georgia/South Carolina coast on Saturday. The latest
guidance has trended away from tropical moisture making its way
inland, therefore a marginal risk was maintained for much of the
Southeast Coast.

Kebede
$$
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FOUS30 KWBC 040814
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
414 AM EDT Sat Oct 4 2025

Day 1 Valid 12Z Sat Oct 04 2025 - 12Z Sun Oct 05 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE EASTERN GREAT BASIN ALONG WITH THE CENTRAL GULF COAST AND
COASTAL GEORGIA DOWN THROUGH THE FLORIDA EAST COAST...

...Eastern Great Basin...

An amplifying upper-level trough advancing through the Great Basin
will be driving multiple waves of low pressure northeastward along
a frontal zone draped across the Intermountain Region. The latest
forecast guidance supports a strengthening mid to upper-level
closed low circulation pivoting across northern UT early this
morning before ejecting through western WY this afternoon. Strong
dynamics/DPVA will ride up across northern UT along with far
southeast ID and western WY which will be interacting with the
front and the pooling of modest instability (MLCAPE ~500 J/kg)
along it for an axis of locally heavy showers and thunderstorms.
Much of this threat will be this morning (notably in the 12Z to 18Z
time frame) as the height falls pivot across the region. The 00Z
HREF guidance suggests some organized convection that will be
capable of producing 1 to 2+ inches of rain which may include some
brief cell-training concerns for areas near and west of the
Wasatch front including around the Great Salt Lake. Can't rule out
there being at least some isolated runoff/flash flooding concerns
from these stronger clusters of convection that evolve this
morning. Therefore, a Marginal Risk of excessive rainfall has been
introduced, but this again is mainly for early in the period today.

...Central Gulf Coast...

A low to mid-level vort center/disturbance over the northern Gulf
of America is forecast to slowly advance westward today which will
help to bring stronger low-level southeast flow and moisture into
southeast LA and coastal MS. Sufficient low-level forcing associated
with the vort energy coupled with at least modest instability with
MLCAPE values of 1000 to 1500 J/kg will support there being at
least scattered bands of convection that will develop and advance
inland across the central Gulf Coast. Some of the 00Z HREF guidance
and recent RRFS solutions suggest some linearly oriented convective
bands potentially setting up that would support some locally
enhanced rainfall totals. Given the improving PW environment with
values of 1.75 to 2+ inches, and a convergent southeast low-level
jet of 30+ kts, some of the rainfall rates may reach or exceed 2
inches/hour. The potential banded nature of the activity may
support some localized rainfall totals going into early Sunday
morning of 2 to 4+ inches. These rains will pose at least an
isolated threat for flash flooding, and especially if any of these
heavier rains were to make into the New Orleans metropolitan area.
As such, a Marginal Risk of excessive rainfall has been introduced
for this period for the central Gulf Coast.

...Coastal Georgia and the Florida East Coast...

Low-level easterly flow will persist today and tonight across the
FL East Coast given the placement of a well-established area of
surface high pressure farther north over the Mid-Atlantic states.
However, the surface ridging is forecast by the models to shift
offshore by later today which will allow for some veering and
strengthening of the Atlantic fetch a bit farther north up into
coastal areas of eastern GA. The latest hires model guidance
suggests a stronger axis of low-level moisture convergence along
with pooling of instability into coastal areas of eastern GA and
near the SC border. Some locally focused bands of relatively shallow/warm-topped convection may attempt impact the coastal
areas here, with some guidance suggesting locally a couple inches
of rain being possible. Farther south, the FL East Coast should
continue to see scattered to broken areas of showers and
potentially a few thunderstorms. However, the activity should
remain disorganized given a lack of deeper layer forcing and only
modest low-level convergence along the coast. The Slight Risk area
that was inherited for the FL Space Coast vicinity has been removed
in favor of a Marginal Risk which will include the north/south
length of the FL East Coast, but extending northward now to the
SC/GA border. Any runoff concerns from heavy rainfall will tend to
be highly isolated and primarily focused over the more urbanized areas.

Orrison


Day 2 Valid 12Z Sun Oct 05 2025 - 12Z Mon Oct 06 2025

...THERE IS MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE CENTRAL GULF COAST, THE SOUTHEAST COAST, AND THE CENTRAL PLAINS...

...Central Gulf Coast...

A weak disturbance in the western Gulf will likely continue to focus
enhanced convergence and convection along portions of the central
Gulf Coast into Sunday. Heaviest rainfall totals may tend to stay
just offshore where the better instability will reside...although
coastal convergence and instability into the immediate coastline
should allow for some heavier cells to make it onshore. Even our
deterministic QPF, which is a multi model blend, brings two day
rainfall totals as high as 3-5" over far southeast LA and right
around 3" along coastal MS and AL. Given the convective nature of
rainfall and PWs over 2" would expect totals to locally exceed these
amounts, and isolated instances of flash flooding are possible. The
00z REFS probabilities of 8" is over 90% across coastal MS/AL. This
is seemingly an under dispersed ensemble in this case, but
interesting nonetheless, and possibly indicative of a lower
probability worst case scenario. Either way, will need to continue
to monitor trends, as can not rule out the need for a Slight risk
along portions of the immediate coast.

...Southeast Coast...

The model QPF signal continues to trend down across the Southeast
coast, although onshore easterly flow, coastal convergence and PWs
around 2" will support localized instances of heavy rainfall.
Overall the flash flood risk appears pretty low, but an isolated
threat can not be ruled out.

...Central Plains...

Convection will likely expand in coverage Sunday evening across
portions of northeast KS, southeast NE and southwest IA. A stalling
frontal boundary will allow for persistent moisture convergence in
the lower levels coupled with a divergence signature aloft. Thus it
seems probable that rainfall will persist through much of the night,
not moving all that much over that time. Whether we see any flash
flood risk evolve will likely come down to the degree of instability
present. It seems likely that we will initially have enough
instability for deeper convection and 1"+ an hour rainfall. However
most indications are that this instability axis will be rather
narrow and under 1000 j/kg. Thus would expect that instability to
get eroded fairly quickly, resulting in decreasing rainfall rates
overnight. Nonetheless, our latest deterministic QPF has 1-2" of
rain, with 2-3" if you include the rain that continues into Monday.
When accounting for convection resulting in locally heavier amounts,
and the possibility that instability ends up greater than forecast
(which a couple models show) then a low end flash flood risk can not
be ruled out.

Chenard


Day 3 Valid 12Z Mon Oct 06 2025 - 12Z Tue Oct 07 2025

...THERE IS MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS EASTERN
FLORIDA AND THE CENTRAL PLAINS...

...Eastern FL...

The 00z ECMWF, AIFS and GEFS mean all suggest an increase in
convective coverage over eastern FL on Monday compared to Sunday.
The approach of a subtle mid level wave may help increase low level
easterly moisture transport while also providing a bit more in the
way of upper divergence. Isolated urban flash flooding should thus
remain a threat into Monday, although would anticipate the risk to
stay quite localized. There has been a clear model trend away from
bringing heavier rainfall into SC/GA and thus the northern extent of
the Marginal risk was cut back.

...Central Plains...

Some convection will likely be ongoing Monday morning across
portions of northeast KS, southeast NE, southwest IA and northwest
MO. The stalled front will remain in the area through the day likely
helping focus additional convection that should only slowly drift
southward. Instability should increase Monday along this front,
however this will coincide with a decrease in moisture transport and convergence along the front. Thus not really anticipating anything
more than a very localized flash flood risk. The threat is likely a
lower end Marginal risk, but given the slow front and two day
rainfall totals of 2", to perhaps as high as 3-4", across this
corridor, localized flooding can not be ruled out. We will maintain
the inherited Marginal risk, but shrink to to better coincide with
the axis of highest two day rainfall totals.

Chenard
$$
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FOUS30 KWBC 050819
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
419 AM EDT Sun Oct 5 2025

Day 1 Valid 12Z Sun Oct 05 2025 - 12Z Mon Oct 06 2025

...THERE IS MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE CENTRAL PLAINS AND MIDWEST ALONG WITH THE CENTRAL GULF COAST
AND EASTERN FLORIDA...

...Central Plains/Midwest...

In the wake of an upper-level trough and surface low transiting
portions of the northern Plains, a cold front will be gradually
settling southeastward today and tonight across the central Plains
and Midwest. Showers and thunderstorms are expected to develop
along the front by this evening across areas of central and
northern KS up through southeast NE and through central IA. MLCAPE
values as high as 1000 to 1500 J/kg are forecast to pool along the
boundary along with a seasonably moist airmass characterized by PWs
of 1.25 to 1.5+ inches. Moisture transport along the front will be
aided by a southwest low-level jet of 30 to 40+ kts going through
00Z this evening which coupled with the instability should help
drive some heavier rainfall rates capable of reaching 1 to 1.5
inches/hour. Going through Sunday night, the convection is expected
to linger as at least modest right-entrance region upper jet
dynamics overhead continue to interact with the front. Some post-
frontal shower and thunderstorm activity is expected as a pool of
elevated instability and frontogenesis lingers over the region. A
consensus of the 00Z HREF guidance supports some spotty 2 to 3+
inch rainfall totals in a narrow axis along the front. Antecedent
conditions are quite dry, but with some localized cell-training
concerns and heavier rainfall totals, there may be some isolated
and mainly urbanized runoff concerns. A Marginal Risk of excessive
rainfall will be maintained across the region.

...Central Gulf Coast...

An elongated low to mid-level low center/trough over the northwest
Gulf of America is expected to focus a corridor of stronger
convergence and moisture transport across the central Gulf Coast
region, with potential for multiple bands of very heavy showers and thunderstorms to evolve. The convection will be embedded within a
deep tropical environment characterized by PWs of 2 to 2.25
inches. This coupled with MLCAPE values of locally near 1500 J/kg
will help favor high rainfall rates that may easily reach 2 to 3
inches/hour with the stronger and more organized convective bands.
The 00Z HREF guidance generally supports the heaviest rainfall
totals remaining confined to the immediate Gulf Coast, however some
localized bands of convection that will be capable of cell-
training may be able to spread a bit farther inland including areas
of south-central to southeast LA through far southern MS and far
southern AL. Some urbanized Gulf Coast locations including New
Orleans and Mobile may be impacted going through Sunday night by
bands of heavy showers and thunderstorms. The latest REFS/RRFS
guidance is more aggressive with the rainfall potential, but a
HREF-led consensus of guidance would suggest some 2 to 4 inch
rainfall totals with spotty 5+ inch amounts not out of the question
where any cell-training occurs. The Marginal Risk area will be
maintained for the time being, with isolated areas of flash
flooding possible, and especially for the aforementioned urban
corridors. However, should the guidance trend any wetter, a Slight
Risk upgrade may be warranted for portions of the central Gulf Coast.

...Eastern FL...

Moist and locally convergent low-level easterly Atlantic flow will
continue along the FL East Coast today. There are some locally
heavier rainfall signals showing up along the Space and Treasure
Coasts and stretching inland somewhat as the potential once again
for some broken bands of locally heavy showers and thunderstorms
sets up. Where any cell-training occurs within these bands, some
spotty rainfall totals of 2 to 4+ inches will be possible. This
may result in there being a highly localized concern for some
runoff problems. A Marginal Risk of excessive rainfall will be
maintained at this time.

Orrison


Day 2 Valid 12Z Mon Oct 06 2025 - 12Z Tue Oct 07 2025

...THERE IS MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
EASTERN ARKANSAS INTO THE OHIO VALLEY AND OVER EASTERN FLORIDA...

...TN and OH Valley...

A Marginal risk was maintained from portions of eastern AR
northeastward into southern IN. 850mb vorticity fields indicate the
tropical disturbance in the Gulf is likely to lift northward on
Monday brining increased PWs and the potential for areas of slow
moving convection. Scattered convection is expected during the day,
although the better focus for high rainfall amounts should come
Monday night as the approaching cold front from the west helps
increase convergence. The environment appears to favor efficient
warm rain processes...with the presence of the low level vorticity
from the Gulf and PWs around or above 2" (over the climatological
90th percentile). Only weak instability is forecast, which could end
up being a limiting factor for flash flooding. However, given the
expected efficient warm rain, there should still be enough
instability to get hourly rainfall rates into the 1-2" range in
spots. The latest WPC deterministic QPF is 1-2" across the area,
although several models indicate locally higher amounts. Given the
environment in place amounts locally getting into the 2-4" range
seems reasonable within the Marginal risk area.

Expect at least localized instances of flash flooding to be
possible, especially by Monday night. There is a bit of uncertainty
regarding the exact rainfall axis, with the new 00z ECMWF shifting
farther east into more of TN and KY. The eastern extent of the
Marginal risk was extended in this direction to account for this potential...although the broader model consensus still favors a
slightly farther west axis, in line with the WPC QPF.

...Eastern FL...

Easterly low level flow will continue to support scattered
convection over eastern FL Monday into Monday night. Model guidance
continues to depict a modest uptick in rainfall coverage and
magnitudes on Monday compared to Sunday. Localized urban flash flood
impacts will remain possible.

...Central Plains...

We opted to remove the Marginal risk that stretched from northeast
KS into southern IA with this update. A localized flash flood risk
still exists on day 1, but by Monday the areas hit hardest on day 1
will be well north of the surface front. Thus most of the
instability will be gone, and rainfall rates should be much lower.
Thus the additional rainfall is not expected to be enough to result
in flash flooding. A bit more instability may reside over MO, but
this is south of the forecast rainfall axis on Sunday, and thus the
rainfall Monday is not expected to be enough to overcome the drier
antecedent conditions here.

Chenard


Day 3 Valid 12Z Tue Oct 07 2025 - 12Z Wed Oct 08 2025

...THERE IS MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE TENNESSEE AND OHIO VALLEY, OVER SOUTHEAST FLORIDA, AND PORTIONS
OF NEW MEXICO...

...TN and OH Valley...

A Marginal risk was maintained from TN northward into portions of OH
and southwest PA. Increasing moisture ahead of an approaching cold
front will likely lead to greater convective coverage and areas of
heavy rainfall. The forcing and moisture will be enhanced by the
same low level vorticity feature that was upstream on Monday and
over the Gulf on Sunday. With PWs forecast over the climatological
90th percentile do expect some warm rain processes, which should
help overcome marginal instability and help produce heavy rainfall
rates. Also note a well defined upper divergence signature centered
over this region within the right entrance region of an upper jet.
Thus the ingredients are there for widespread rainfall and at least
some pockets of heavy rates.

The main question for flash flood potential will be the duration of
these higher rates. Overall the front looks pretty progressive,
which should limit this duration. However, guidance does indicate
that some training could occur for a period Tuesday before the front
clears through, with the favored axis somewhere in the vicinity of
central to eastern KY. While differing on location, most 00z
deterministic models indicates a swath of 2-3" of rainfall, which
seems reasonable given the environment in place. In fact would not
be surprised if totals locally exceed 3". Overall this seems like a
solid Marginal risk with localized areas of flash flooding probable.
Can not rule out an embedded Slight risk upgrade on future updates
pending model trends.

The northern extent of the Marginal risk was cut out of the
Northeast with this update. Instability really drops off with
northern extent which will impact rainfall rate potential. These
lower rates combined with the drought conditions suggest flash
flooding is unlikely. We would probably need higher rates to overcome
the dry soil conditions, and this seems unlikely given the currently
forecast instability. So it is looking more like a beneficial
rainfall, with most areas around 0.75" but locally as high as 1.25" or so.

...Southeast FL...

Expecting another day of scattered convection within the easterly low
level flow Tuesday. Compared to previous days the threat should
mostly be focused over southeast FL by this time, and a localized
urban flash flood risk is possible.

...NM...

A Marginal risk was maintained for portions of central and eastern
NM on Tuesday. Easterly low level post frontal flow will help
locally enhance convergence and upslope and scattered convection is
likely to develop. With PWs around 1" and CAPE only forecast between
500-1000 j/kg this is likely a lower end threat. Nonetheless,
locally heavier convection with high rates could result in isolated
flash flooding, particularly over any more sensitive burn scars or
basins.

Chenard
$$
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FOUS30 KWBC 060819
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
419 AM EDT Mon Oct 6 2025

Day 1
Valid 12Z Mon Oct 06 2025 - 12Z Tue Oct 07 2025

...THERE IS SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE MID-SOUTH AND LOWER OHIO VALLEY...

...Mid-South/Lower Ohio Valley and the Central Gulf Coast...

An elongated low to mid-level vort center near the central Gulf
Coast will lift northward into the Mid-South today and gradually
stretch northeastward into portions of the Lower OH Valley by later tonight through early Tuesday morning. Increasingly convergent flow around
the eastern flank of the vort energy and an associated weak surface
low/trough axis coupled with enhancing moisture transport aided by
a 30 to 40 kt low-level jet will support broken bands of heavy
showers and thunderstorms. Modest instability with MLCAPE values of
500 to 1000 J/kg will be in place with the aid of diurnal heating,
but the vertical column will be quite moist with CIRA-ALPW data
showing the aforementioned vort energy embedded within a rather
deep tropical environment characterized by PWs of 2 to 2.25 inches.

Relatively warm-topped convection with high WBZ levels will support
very efficient rainfall processes for high rainfall rates as this
energy lifts north over the next 12 to 24 hours. The latest 00Z
HREF guidance supports broken convection with rainfall rates as
high as 1.5 to 2.5 inches/hour, and some concerns for some cell-
training that may foster some localized totals of 3 to 5 inches.
The more concentrated areas of convection are most likely to focus
across areas of eastern AR/western TN northeastward up into western
KY and southern IN going through Monday night and Tuesday morning
where the axis of stronger low-level convergence in conjunction
with some modest upper-level jet forcing/divergence is forecast to
become aligned. A Slight Risk of excessive rainfall will be
maintained for this period, with some southward expansion of it
depicted down across eastern AR compared to continuity given the
latest multi-model hires consensus. The setup will be conducive
for there being isolated to scattered areas of flash flooding which
will include urbanized flooding concerns.

Meanwhile, very moist and convergent low-level southerly flow off
the Gulf coupled with a moderately unstable boundary layer will
favor a threat for additional small-scale bands of convection to
impact parts of eastern LA along with coastal areas of southern
MS, southwest AL and into the western FL Panhandle. PWs running
close to or above 2 inches coupled with the instability will yield
high rainfall rates, with some localized additional rainfall totals
for this period of 2 to 4+ inches possible. This is supported by
the 00Z HREF guidance, and the setup will support isolated concerns
for runoff problems/flash flooding. As a result, a Marginal Risk
of excessive rainfall has been expanding to encompass these areas.

...Eastern FL...

Moist easterly low-level flow will continue to support scattered
areas of convection over eastern FL today through tonight. The
activity again should tend to be rather disorganized, but there
will be some potential for small-scale east/west oriented bands to
set up that may result in some isolated 2 to 4+ inch rainfall
totals. This may drive at least some isolated runoff concerns. As a
result, the Marginal Risk of excessive rainfall is maintained for
this period.

Orrison


Day 2
Valid 12Z Tue Oct 07 2025 - 12Z Wed Oct 08 2025

...THERE IS SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE OHIO VALLEY...

...Ohio Valley into the Central Appalachians...

A Slight risk was maintained from portions of northern TN into much
of KY, southern IN and OH, and western WV where isolated to
scattered flash flooding is likely. Increasing southerly flow ahead
of an approaching cold front will advect moisture northward while
also enhancing lower level convergence. Also of note is a sfc-850mb
low that is over AR today and was over the northern Gulf on Sunday.
This feature will get more elongated in nature by Tuesday, but
should still act to locally increase moisture transport and
convergence over KY and surrounding areas. PWs are forecast around
2", which is well over the 90th percentile for this time of year.
Instability is expected to only be modest, generally in the 500-1000
j/kg range, however the strong synoptic forcing provided by the
approaching front and good upper level divergence should compensate
for this and still allow for organized convection.

Both the 00z HREF and REFS show moderate to high probabilities of
hourly rainfall exceeding 1", but only low probabilities of
exceeding 2". The limited instability is likely responsible for
the lack of 2"+ per hour rainfall rates. However the deep saturated
layer and low topped convection supports highly efficient warm rain collision-coalascence processes, leading to the likelihood of at
least 1" per hour rainfall.

The main question for flash flood potential will be the duration of
these higher rates, as it seems unlikely that 1hr FFG will be
exceeded. While the front will be progressive, it does look like we
will have enough convective coverage to support some training, and
at least a few hours of heavy rainfall rates. Thus while 1hr FFG may
be difficult to overcome, it does look like there will be an
opportunity for some exceedance of the 3hr FFG...with both the 00z
HREF and REFS showing exceedance probabilities upwards of 25-50%.
The latest WPC QPF indicates event total rainfall of 2-4" over most
of the Slight risk area, which is supported by high HREF and REFS
neighborhood probabilities of exceeding 3". Also will note that
there are even moderate probabilities of locally exceeding 5" with
this event.

There is a bit of model spread on the most favored axis for heaviest
rainfall and flash flooding. Both the HREF and REFS supports a
slightly farther southwest axis across KY and northern TN, with the
global guidance generally more over eastern KY into WV. The Slight
risk was made big enough to support a compromise of these two camps,
and will need to continue to monitor trends going forward. Generally
think the highest risk is over KY, but can no rule out that shifting
into northern TN or portions of WV.

While the rainfall does look a bit more convective now over the
Northeast, 1" per hour probabilities are still low...with most
guidance peaking rainfall rates in the 0.5"-0.75" range. Given the
ongoing drought conditions it still seems unlikely that these rates
will be high enough to overcome the dry soil conditions. Thus even
with rainfall totals approaching 1.5" we will continue with no risk
area depicted.

...Southeast FL...

Expecting another day of scattered convection within the easterly low
level flow Tuesday. Compared to previous days the threat should
mostly be focused over southeast FL by this time, and a localized
urban flash flood risk is possible.

...NM...

The convective threat looks a bit better than it did this time last
night with models trending a bit more robust with development.
Easterly low level post frontal flow will help locally enhance
convergence and upslope and scattered convection is likely to
develop. Instability is forecast to be modest, but may get towards
1000 j/kg, which would be enough for heavy rainfall rates given the
anomalous PWs in place. The high res guidance is starting to show a
threat of 1"+ per hour rainfall, which would be enough for isolated
flash flooding.

Chenard


Day 3
Valid 12Z Wed Oct 08 2025 - 12Z Thu Oct 09 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
NEW MEXICO...

Looking at a continuation of the localized heavy rainfall threat over
NM into Wednesday. The moisture plume and instability axis will
expand westward which should expand the isolated flash flood risk in
that direction as well. The environmental ingredients look pretty
similar to Tuesday, as do model QPF forecasts. So would generally
expect similar convective coverage and intensity with isolated flash
flooding again a concern.

Chenard
$$
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FOUS30 KWBC 070829
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
429 AM EDT Tue Oct 7 2025

Day 1
Valid 12Z Tue Oct 07 2025 - 12Z Wed Oct 08 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
KENTUCKY, MIDDLE TENNESSEE, THE UPPER OHIO VALLEY, AND NEW MEXICO...

...Mid-South through the Upper Ohio Valley and Central Appalachians...

A weak mid-level vorticity maxima (currently over far northeastern
Arkansas) will trek east-northeastward across Kentucky through
most of the day. This feature will likely maintain at least some of
its organization given persistent convection near and east of its
center and sufficient downstream instability. Areas of 1-3 inch
rainfall totals are expected with this feature, and an uptick in
convective coverage should occur later today as surface heating
promotes destabilization within a moist airmass downstream of the
feature. Slow cell movement and localized training/backbuilding are
both expected to prompt areas of excessive runoff through the
forecast period especially within the Slight Risk area.

Later today, height falls from a larger scale trough centered over
Hudson Bay will aid in additional convection along a front that
will sweep through the region. Storms may redevelop across Kentucky
and Tennessee, although the degree of coverage will be heavily
modulated by the degree of lingering instability behind the initial
wave of daytime convection expected across those areas. A pool of
at least 1.5 inch PW values should remain - supporting heavy
rainfall with any lingering convection through the evening hours.

Additional convection is expected along the aforementioned cold
front across New York State and western New England. Storm motions
should be relatively fast (30+ knots), limiting any heavy rainfall
to any localized areas of training that can materialize.
Additionally, antecedent dryness/drought should limit excessive
runoff potential. A Marginal risk extends to western Pennsylvania
and vicinity - although this risk seems a bit too isolated farther
northward to include or expand in any probabilities at this time.

...New Mexico...

A southwestward moving cold front will stall close to the higher
terrain across central New Mexico today through tonight. Upslope
flow behind this front and weak mid/upper waves traversing the
state will both initiate deep convection within a sufficiently
moist airmass (0.7-1.25 inch PW) for heavy rainfall. Storm motions
across northern portions of the state may be quick enough to limit
rainfall, yielding a mostly isolated flash flood threat in areas
that are sensitive (i.e., burn scars, low-lying areas). Central and
southern portions of the state should experience slower storm
motions and perhaps multiple rounds of convection from afternoon
through the overnight hours. Given increase in convective coverage
and potential for local 3+ inch rainfall totals occurring
perilously close to sensitive areas/burn scars, a Slight Risk was
introduced with the expectation of at least a few instances of
excessive runoff given the scenario.

...Southeastern Florida...

Local 1-2 inch rainfall totals are expected across urban areas of
Southeastern Florida from Miami northward through West Palm Beach
and Port Saint Lucie. The greatest risk of these downpours
materializing will occur from midday onward due to peak heating/destabilization. Additionally, onshore flow/coastal
flooding may hinder runoff processes beneath any heavier downpours,
locally enhancing flash flood risk. One or two instances of flash
flooding cannot be ruled out, and a Marginal Risk is in place to
address the threat.

Cook


Day 2
Valid 12Z Wed Oct 08 2025 - 12Z Thu Oct 09 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF NEW MEXICO AND EASTERN ARIZONA...

Some continuation of heavy rainfall potential will exist across New
Mexico during the early morning hours of the D2/Wed forecast
period. During the day, an increase in insolation/destabiliztaion
should promote development of isolated to scattered thunderstorms
initially along terrain/ridgelines near the Arizona/New Mexico
border and across the southern Rockies. Storms will drift
slowly/erratically while producing brief heavy rainfall. Typical
low spots/sensitive areas will experience a flash flood threat with
this activity. Coverage of flash flood potential should be sparse
enough to warrant continuation of a Marginal Risk and associated
probabilities.

Cook


Day 3
Valid 12Z Thu Oct 09 2025 - 12Z Fri Oct 10 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS A LARGE
PART OF THE SOUTHWEST AND SOUTHEASTERN FLORIDA...

...Southwest...

Models are consistent in depicting a dramatic increas in
atmospheric moisture content across the Colorado River Valley from
both Hurricane Priscilla and the Gulf of California. Widespread
1-1.75 inch PW values are expected by midday Thursday. This
moisture will combine with deep southwesterly steering flow and
weak mid-level waves aloft to produce several areas of
precipitation throughout the forecast period (including the
overnight and early morning hours). A close inspection of point
forecast soundings from model data casts some doubt on the extent
of instability developing within the moist axis due to widespread
cloud cover. Any daytime destabilization within the region will
likely lead to stronger convection and an increased risk of flash
flooding. Trends in instability will be monitored for possible
upgrades in parts of the Marginal Risk area in later outlooks.

...Southeastern Florida...

Models depict a few areas of convection developing very close to
urbanized areas of southeastern Florida during peak heating hours.
Point forecast soundings across the area depict typically
moist/unstable profiles (2+ inch PW values), though wind fields are
very weak, suggesting slow/erratic cell movement and mergers. Spots
of 1-3 inch/hr rain rates could materialize, supporting an urban
flash flood risk across the area.

Cook
$$
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FOUS30 KWBC 080809
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
409 AM EDT Wed Oct 8 2025

Day 1
Valid 12Z Wed Oct 08 2025 - 12Z Thu Oct 09 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF NEW MEXICO AND EASTERN ARIZONA...

Ongoing shower and thunderstorm activity will exist on an isolated
basis across central and south-central New Mexico near higher
terrain. Slow movement, localized backbuilding, and proximity to
burn scars will be the likely modulators of flash flood potential
through the early morning hours.

Later in the afternoon, thunderstorm activity is expected to
develop across western New Mexico and eastern Arizona in an
environment characterized by 0.7-1.0 inch PW values, mid-level
instability, and weak wind fields beneath 500mb. Slow moving cells
with brief heavy rainfall are likely, though coverage should remain
isolated. The greatest flash flood threat should exist where
heavier rain can materialize in/near typical low spots/burn scars.
Most of this activity should be diurnally driven, with weakening
expected in tandem with low-level stabilization after the 03-06Z timeframe.

Cook


Day 2
Valid 12Z Thu Oct 09 2025 - 12Z Fri Oct 10 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHWEST AND EASTERN FLORIDA...

...Southwest...
Moisture content across much of the Southwestern U.S. will increase dramatically in tandem with strengthening southerly mid-level flow
downstream of a mid-level trough along the California coast and
trajectories emanating from Hurricane Priscilla. Modest surface
heating will allow for areas of convection to drift northeastward
across the Marginal Risk area throughout the day - perhaps
beginning as early as 12Z Thursday. Models depict the greatest risk
of deeper convection occurring from northwestern Arizona into
southwestern Utah during the afternoon/evening, and some of this
development could extend into southern Nevada as well. Additional
thunderstorm activity may occur across the eastern Transverse and
Peninsular Ranges in southern California on an isolated basis. The
primary mitigating factor for a more widespread flash flood risk
is limited insolation/surface warming due to cloud cover. One or
two focused corridors for heavier precipitation may develop within
the broader Marginal contingent on stronger destabilization due to
afternoon sunshine. Should this scenario materialize, a small area
of higher probabilities/ and categorical Slight Risk may be needed.

...Florida...
Models (particularly CAMs) depict deep moist convection across the
east coast of Florida during the afternoon and evening hours. As
typical for the region, abundantly moist thermodynamic profiles
will combine with weak kinematics for slow-moving cells with local
2-3 inch/hr rates at times on an isolated basis. These cells will
pose an urban flash flood threat from Daytona Beach southward to
Miami/Dade metro. Weak onshore flow has also contributed to a
coastal flood risk that might hinder runoff potential and
exacerbate flood concerns on a localized basis.

Cook


Day 3
Valid 12Z Fri Oct 10 2025 - 12Z Sat Oct 11 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS NORTHERN
ARIZONA, SOUTHERN UTAH, AND SOUTHWESTERN COLORADO...

...Southwest...
A second consecutive day of abundant moist advection will be
underway during the D3 forecast period as Priscilla drifts
northward and a slow-moving mid-level trough persists along the
California coastline. Models are generally higher with instability
parameters (500-1000 J/kg MUCAPE) compared to prior days across
the Marginal and Slight Risk areas while maintaining abundantly
moist profiles (PW values ranging from 1-2 inches). Areas of
heavier rain are expected, with deeper convection possible in the
Slight Risk area from northern Arizona into southwestern Colorado.
Some of these heavier downpours will occur atop sensitive
terrain/slot canyons and burn scars - posing a locally significant
flash flood risk. While specific timing of convection remains a
challenge at this timeframe, it is possible that multiple rounds of
convection develop and migrate northeastward across the region
throughout the forecast period. Widespread 1 inch rainfall totals
are expected, with local amounts potentially exceeding 3 inches in
a few spots.

...Southeastern U.S. Coastline...
Models are in agreement that a low pressure will develop and
strengthen substantially over the Gulf Stream just east of Florida
during the forecast period. Low-level easterlies will strengthen
dramatically and eventually become northeasterly during the
forecast period. These low-level wind fields will contribute to a
coastal flood risk while also hindering runoff processes near areas
that experience heavy rainfall. The heavy rainfall threat is a bit
conditional especially with northward extent across the Carolinas
coastlines. Nevertheless, model guidance generally depicts a few
areas of heavy rainfall especially across eastern Florida during
the first half of the Day 3 forecast period (Friday morning).
Trends will need to be monitored for any westward trend in
development of this low closer to land areas, which may increase
the heavy rainfall threat substantially. At this time, isolated
flash flood/runoff issues are expected, warranting continuation of
a Marginal Risk along coastal areas.

Cook
$$
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FOUS30 KWBC 090745
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
345 AM EDT Thu Oct 9 2025

Day 1 Valid 12Z Thu Oct 09 2025 - 12Z Fri Oct 10 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS SOUTHEASTERN
CALIFORNIA, SOUTHERN NEVADA, SOUTHWESTERN UTAH, AND WESTERN ARIZONA...

...Southwest...

Models/observations all continue to suggest that a dramatic
increase in low- and mid-level moisture content should occur across
the Southwestern U.S. in tandem with eastward movement of a broad
mid-level trough just west of California and moist mid-level
trajectories emanating from Priscilla. At least a few pockets of
surface heating should occur beneath the moisture plume, resulting
in sufficient surface-based instability for deeper convection
during the afternoon and evening. Efficient rainfall processes
should occur with any storms that form due to the aforementioned
moisture content (with PW values reaching nearly 2 inches across
southwestern Arizona/far southeastern California). Mid-level wind
fields suggest potential for appreciable (20-30 knot) storm
motions, although the tendency for convection to train and occur
on/near sensitive ground conditions (i.e., burn scars, slot
canyons) are all suggestive that at least a few instances of flash
flooding can be expected during the forecast period. Models are
also suggestive of continued precipitation potential overnight
despite a loss of surface heating - likely due to ascent from both
Priscilla and the mid-level trough off the West Coast. Several
areas of 1 inch rainfall totals are possible, and isolated 2-2.5
inch totals could also occur.

...Florida...

Models continue to produce deep moist convection across the east
coast of Florida during the afternoon and evening hours. Widespread
1-3 inch rainfall amounts are expected. As typical for the region,
abundantly moist thermodynamic profiles will combine with weak
kinematics for slow-moving cells with very high rainfall rates
(exceeding 2 inches/hr at times). These cells will pose an
urbanized flash flood threat from Jacksonville metro southward
through Miami/Dade. Weak onshore flow has also contributed to a
coastal flood risk while hindering runoff processes in a few
locales. This could exacerbate flood/flash flood concerns on a
localized basis.

Cook


Day 2 Valid 12Z Fri Oct 10 2025 - 12Z Sat Oct 11 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF ARIZONA...

...Southwest...

A synoptically evident heavy rain threat is expected to unfold
across the region Friday into early Saturday. Models continue to
depict a large-scale trough just west of the California coastline
that should slowly move eastward and spread geopotential height
falls across much of the Southwest and Great Basin. 00Z models have
sped up the timing of the absorption of Priscilla (perhaps
remnants of Priscilla by this forecast timeframe) within the
broader-scale trough and now depict them directly impacting
portions of Arizona by as early as 18Z Friday. Ascent from
Priscilla, ascent from the larger-scale trough, and abundant
moisture streaming into much of the Great Basin (with attendant
terrain influences) all point to potentially widespread flash
flooding during the forecast period. Of note - the overall synoptic
pattern has notable parallels to early October 2018, when remnants
of Hurricane Rosa moved into the Great Basin and prompted
extensive flash flood impacts across central Arizona.

The Moderate Risk has been introduced across portions of central
into northeastern Arizona where models (particularly the GFS and
ECMWF) depict multiple hours of repeating thunderstorm potential
especially focused near terrain-favored areas of the Mogollon Rim.
Widespread 1-2 inch rainfall amounts (and locally higher totals)
can be expected. Significant impacts are possible given the
prolonged heavy rainfall potential. While specific timing of
convective axes are still unclear at this timeframe, some eastward
progression of the heaviest rainfall is generally depicted by most
model guidance, with precipitation areas potentially reaching the
AZ/NM border region through 12Z Saturday.

Outside of the Moderate Risk area, models depict potential for
scattered thunderstorms to occur throughout the forecast period
from southeastern California northeastward through eastern Utah and southwestern Colorado. A few instances of flash flooding will
remain possible especially near urban areas, burn scars, and slot canyons.

...Southeastern U.S. Coastal Areas...

Models continue in agreement that an organizing area of low
pressure will strengthen over the southern Gulf Stream (east of
Florida) during the forecast period. Models are also in agreement
that at least a few spots along the coast will experience heavy
rainfall at times through 12Z Saturday - especially in eastern
Florida. This heavy rainfall potential will occur in conjunction
with dramatically strengthening onshore flow across coastal areas
that should promote flooding while hindering runoff. This "combo-
flood threat" (both freshwater and saltwater flooding) will exist
across coastal areas throughout the forecast period while peaking
fairly early across the east coast of Florida (between 12Z Friday
and 00Z Saturday) and peaking across coastal Carolinas areas from
00Z Saturday through the end of the forecast period (12Z Saturday).

Cook


Day 3 Valid 12Z Sat Oct 11 2025 - 12Z Sun Oct 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
FOUR CORNERS STATES AS WELL AS FOR PORTIONS OF COASTAL NORTH
CAROLINA AND VIRGINIA...

...Southwest...

Predominant southwesterly flow ahead of a deep longwave trough
progressing east from the West Coast to over the Intermountain West
will draw plentiful tropical moisture from the remnants of Priscilla
into the Four Corners Region. This will spike atmospheric moisture
levels over portions of Arizona to as high as 5 sigma above normal.
Thus, moisture availability for rainfall will not be a limiting
factor in the slightest (pun intended). However, what will limit the
potential for more significant flooding will be a lack of
instability. While the remnants of Priscilla will bring some
instability northward, for most areas MUCAPE values are expected to
remain under 1,000 J/kg. Thus, the areas of heaviest rainfall will
be focused on south and west facing slopes, as upslope becomes a
primary localized forcing mechanism. With a Moderate Risk upgrade on
Day 2, a higher end Slight is in effect for the portions of the
Mogollon Rim expected to be hardest hit from the aforementioned
upslope continuing into Day 3.

The Slight up to the 4 Corners/southwest Colorado remains unchanged
with this update. Similar to further south and west, upslope will be
a primary forcing mechanism, in addition to the upper divergence
ahead of a strong shortwave which will push east from California to
over Utah by Sunday morning. This too will locally increase the
forcing needed to squeeze out additional rainfall into the San Juans
throughout the period.

Finally, the inherited Marginal Risk was expanded north to cover
much of central Montana with this update. Additional shortwave
energy, perhaps moving even faster than the energy further south,
will allow for a localized negative tilt to the shortwave, which
should greatly increase the forcing needed for widespread light to
moderate rainfall into central Montana. A potent cold front
associated with the approach of the upper level trough will also
locally increase rainfall rates ahead of the front. See the Heavy
Snow Discussion (HSD) for additional details on the snowfall
potential in the higher elevations of western Montana with this same disturbance.

...Mid-Atlantic Coast...

The center of a large and slow-moving Nor'easter will make its way
up the coast from off Jacksonville, FL Saturday morning to near
Wilmington, NC by Sunday morning. The expansive precipitation shield
associated with this large low will be impacting the coast of the
Carolinas already at the start of the period, with its northernmost
extent moving into southern New England by the end of the period
Sunday morning. The biggest rainfall threat with this storm will be
across coastal North Carolina and Virginia. The guidance is in
reasonable agreement that once the center reaches near the border of
the Carolinas, it's forward speed will slow to a crawl through
Saturday night. This will allow the comma-head region of the storm
to sit in place across coastal North Carolina and Virginia for a
long-duration, likely lasting into the D4/Sunday period. Meanwhile
strong and gusty northeast winds will pile up tidal/ocean water at
the coast. While coastal flooding concerns are likely to be a much
more significant concern as far as magnitude of impacts, ocean water
backing up the mouths of bays, rivers, and inlets is likely to
significantly impede draining the fresh water that falls from
rainfall, resulting in more widespread flooding concerns from the
combination of the two sources of water.

The Slight Risk remains in effect for all of coastal North Carolina,
and has been expanded north to include the Hampton Roads area, for
similar combination of tidal and fresh water flooding likely to
impact the urban area there as well. The primary piece of
uncertainty, which is the biggest motivator to keep the flooding
risk at a Slight, is how much instability can work into the system's precipitation north of the low center. The expected lack of
instability, albeit increasing and with convection moving from
higher instability areas to the south into lower instability areas
to the north, supporting persistence, should limit precip rates to
usually more manageable levels, which therefore will limit the
instances of flash flooding, but that is highly dependent on the
low's track and definitely could change.

Wegman
$$
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FOUS30 KWBC 100807
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
407 AM EDT Fri Oct 10 2025

Day 1
Valid 01Z Fri Oct 10 2025 - 12Z Fri Oct 10 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF ARIZONA AND SOUTHERN UTAH...

...Southwest...

Overall, not much change to the previous forecast, with widespread
showers and storms expected to develop across the region today into
tonight, producing moderate to heavy accumulations, with numerous
flash floods possible.

An amplified upper trough centered along the West Coast will slowly
shift east. Mid level energy embedded within the base of the
trough, along with energy associated with Tropical Cyclone
Priscilla, will converge upon the Southwest today. This energy,
interacting with moisture associated with the tropical system will
support widespread showers and storms, with repeating development
possible. Guidance continues to indicate impressive PW anomalies -
over 5 std dev above normal in some locations according to the GFS.
And while instability may be generally modest across much of the
region, deep saturation through the column will support efficient
rainfall rates, possibly reaching 1-2 in/hr at times.

A Moderate Risk remains in place across central into northern
Arizona, reflecting higher probabilities for amounts over 2 inches
from both the HREF and RRFS. A second Moderate Risk area was added
over portions of southern Utah, including the more vulnerable slot
canyon and national park areas. Overnight hi-res guidance has
trended up across this area, showing storms training from southern
Nevada into the region, with probabilities for amounts over 2
inches increasing. Higher probabilities for similar amounts also
center along the upslope areas of the San Juans. Currently
considered a higher-end Slight, this area may also be considered
for an upgrade later today.

...Southeastern U.S. Coastal Areas...

An area of low pressure will become better organized east of
Florida this period. As the system strengthens, onshore winds
north of the center will begin to direct deeper moisture toward
the coast. However, the overnight hi-res guidance continues to
indicate that the greater instability will remain offshore,
confining the threat for heavy amounts to the immediate coast.
While widespread heavy rains are not expected, coastal flooding
driven by the strong onshore winds, may elevate runoff concerns for
any rains that do fall across the area.

Pereira


Day 2
Valid 12Z Fri Oct 10 2025 - 12Z Sat Oct 11 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
FOUR CORNERS STATES AS WELL AS FOR PORTIONS OF COASTAL NORTH
CAROLINA AND SOUTHEASTERN VIRGINIA...

...Southwest to the Northern Rockies...

Overall, not much change to the previous forecast.

Heavy rain with flash flooding will remain a concern from the
Southwest into the central Rockies, as deep tropical moisture
continues to spread north. While moisture and energy associated
with the remnants of Tropical Cyclone Priscilla will be quickly
lifting north, additional moisture emanating from Tropical Cyclone
Raymond will begin to spread into the Southwest as well. This
combination of moisture and increasing upper level jet support will
likely produce another day of widespread shower and storm
development, albeit a bit further east than the previous day, with
the greater threat for heavy rain and flash flooding centered over
central and southeastern Arizona and over the San Juans. Although
instability may again be limited, the available moisture and lift
may be sufficient to support rainfall rates over 1 in/hr in some locations.

Farther north, moisture will be drawn out ahead of a highly-
amplified upper trough. While rates may be less intense, this
combination of moisture and strong lift may generate showers and
storms that produce localized runoff concerns as far north as
parts of southwestern and central Montana before snow levels begin
to fall late in the period.

...Mid-Atlantic Coast...

There remains uncertainty in the exact track of a low-pressure
system that is forecast to deepen as it moves along the Southeast
and Mid Atlantic coasts this period. What remains more certain is
the heavy rain that is likely to impact portions of eastern North
Carolina and southeastern Virginia. Deep moisture (PWs 1.75-2
inches) along with strong forcing will support heavy rains within
the associated comma-head. The heaviest amounts are expected to
focus across coastal North Carolina, with some deterministic models
indicating that several inches are possible. Similar to the
previous period, a tight east-to-west gradient is likely. However,
as the system intensifies, expect some heavier amounts to spread
further inland than during the previous period. Compound flooding
will remain a concern as coastal flooding generated in part by
strong onshore winds combines with the runoff from the heavy rain.

Pereira


Day 3
Valid 12Z Sat Oct 11 2025 - 12Z Sun Oct 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHERN ARIZONA AND NEW MEXICO, FAR WEST TEXAS, AND ALONG
PARTS OF THE MID ATLANTIC COAST...

....Southeastern Arizona, Southwestern New Mexico, and Far West Texas....

The pattern will remain active for at least a part of the Southwest
as moisture and energy associated with the remnants of Tropical
Cyclone Raymond move into the region. Anomalous moisture along
with large-scale ascent afforded in part by favorable upper jet
forcing will support widespread precipitation and the potential for
heavy amounts from southeastern Arizona to Far West Texas.

...Mid Atlantic and the Northeast...

A coastal low will continue its slow track to the north along the
northern Mid Atlantic this period, with strong onshore winds
driving deeper moisture and the potential for heavy rains north of
the center. The track of the storm and rainfall details remain
uncertain. However, widespread moderate to heavy rain is expected
from the northern Mid Atlantic coast to southern New England, with
coastal flooding likely to compound runoff concerns where heavy
rain does occur.

Pereira
$$
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FOUS30 KWBC 110832
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
432 AM EDT Sat Oct 11 2025

Day 1
Valid 12Z Sat Oct 11 2025 - 12Z Sun Oct 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
FOUR CORNERS STATES AS WELL AS FOR PORTIONS OF COASTAL NORTH
CAROLINA AND SOUTHEASTERN VIRGINIA...

...Southwest to the Northern Rockies and High Plains...

An amplified upper trough will move east from the West Coast to
the Rockies. Deep southwesterly flow ahead of the trough will
continue to transport tropical moisture and energy north from the Southwest/Four Corners Region early in the period. The GFS is
showing PW anomalies of 4-5 std dev above normal from the Southwest
into the central Rockies this morning, with anomalies increasing
further to the north into the northern Rockies/High Plains as the
trough continues to shift east later today.

Moisture and energy associated with the remnants of Tropical
Cyclone Priscilla will continue to lift north from the
Southwest/Four Corners region, but residual moisture left in its
wake will maintain significant anomalies from the Southwest up
through Four Corners before a front associated with the upper
trough brings in drier air through the Four Corners by tonight.
However, PW anomalies are expected to remain notably high across
southeastern Arizona and southwestern New Mexico, where moisture
moving out ahead of Tropical Cyclone Raymond is expected to spread
into the region.

Overall, not much change to the previous outlook areas, with a
Slight Risk extending from the Southwest through the Four Corners
into the central Rockies, where moisture and energy associated with
Priscilla are expected to support widespread precipitation,
producing locally heavy amounts early in the period. Both the HREF
and RRFS show high probabilities for accumulations exceeding an
inch covering much of the western Colorado ranges, with high
neighborhood probabilities for amounts exceeding 2 inches centered
over the San Juans. Further to the south, hi-res guidance show
showers and storms firing later today, with repeating development
across portions of southern Arizona and New Mexico. Both the HREF
and RRFS show high probabilities for amounts over 2 inches centered
along the Mogollon Rim into southeastern Arizona and portions of
southwestern New Mexico.

Lastly, across the northern Rockies and High Plains, strong ascent
afforded in part by favorable upper jet forcing, interacting with
the previously noted anomalous moisture plume spreading north, may
be sufficient to produce some locally heavy amounts, with isolated
runoff concerns from eastern Idaho and western Wyoming into parts
of southwestern and central Montana today.

...Coastal Carolinas and Southeastern Virginia...

An area of low pressure now organizing east of Florida will
continue to deepen and track north this morning, before slowing as
it reaches the Carolina coast later today. Strong easterly winds
north of the center will draw deep moisture inland, with heavy rain
likely to impact coastal North Carolina this evening into the
overnight before reaching into southeastern Virginia during the
overnight as well. Models continue to show the potential for
several inches along the North Carolina coast, but with a tight
gradient further inland. Maintained a Slight Risk across coastal
North Carolina into southeastern Virginia, where in addition to
heavy rain, coastal flooding generated by the strong onshore winds
is likely to compound runoff concerns.

Pereira


Day 2
Valid 12Z Sun Oct 12 2025 - 12Z Mon Oct 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHERN ARIZONA AND NEW MEXICO...

...Southern Arizona to West Texas...

Anomalous moisture will remain in place, fortified by moisture
associated with the remnants of Tropical Cyclone Raymond pooling
along the frontal boundary settling into the area. This moisture
interacting with increasing ascent afforded by mid level energy and
favorable upper jet forcing will support additional showers and
storms, with the potential for heavy rain and flash flooding.
Maintained a Slight Risk, but reduced its footprint across the
region. Overall, the 00Z models have trended lighter across the
U.S., with the heaviest amounts focused south of the U.S.-Mex
border. There still remains a decent signal for at least locally
heavy amounts to develop, so a Slight Risk was maintained across
portions of southeastern Arizona into far southwestern New Mexico,
with a Marginal Risk extending farther east into West Texas.

...Mid Atlantic Coast to Southern New England...

Models continue to differ on the details on how the low pressure
along the East Coast will evolve this period. The general consensus
of the models shows an area of low pressure lingering and weakening
over the Mid Atlantic, as a second low begins to develop along the
Northeast Coast as its associated frontal system interacts with a
northern stream low becoming cutoff over the Northeast. The models
however differ on the amplitude and track of the system, lowering
confidence in the precipitation forecast over the Northeast.
Regardless of development, easterly winds will spread at least some
moderate to locally heavy amounts from the northern Mid Atlantic
coast northward into southern New England, with coastal flooding
remaining a compounding concern. Given the uncertainty, with
several models keeping heavy amounts offshore, opted to remove the
Slight Risk for now. However, should the 00Z ECMWF be the start of
a trend toward a more amplified/westerly solution, a Slight Risk
may be reintroduced.

Pereira


Day 3
Valid 12Z Mon Oct 13 2025 - 12Z Tue Oct 14 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTHEASTERN ARIZONA, SOUTHWESTERN NEW MEXICO, AND SOUTHERN
COLORADO...

...Southwest to the Central Rockies...

Backing flow ahead of a deep low dropping south into northern
California will draw lingering anomalous moisture over the
Southwest back to the north into the central Rockies. This moisture
interacting with favorable mid to upper level forcing will generate
additional showers and storms, with guidance indicating an elevated
chance for locally heavy amounts and flash flooding concerns over
portions of southeastern Arizona, southwestern New Mexico, and the
San Juan Mountains.

...Northern and Central California....

Models are in generally good agreement showing an anonymously deep
upper developing and dropping south along the West Coast from the
Pacific Northwest to Northern California this period. Moisture with
the system will be relatively modest initially, but enough to
raise moisture anomalies to over a std dev above normal along its
axis of strong onshore flow. This along with strong forcing may be
sufficient to produce locally heavy amounts, with isolated runoff
concerns, especially in the upslope regions of the coastal ranges
and the Sierra foothills.

....Northeast...

Plenty of questions remain as to how the low developing along the
Northeast coast will continue to evolve, but most agree on at least
a localized threat for heavy rain centered along the southeastern
New England coast continuing into the period.

Pereira
$$
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FOUS30 KWBC 120806
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
406 AM EDT Sun Oct 12 2025

Day 1
Valid 12Z Sun Oct 12 2025 - 12Z Mon Oct 13 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHERN ARIZONA AND NEW MEXICO...

...Southwest...
Deep moisture, fortified with the remnants of Tropical Cyclone
Raymond, will remain in place over portions of southern Arizona and
New Mexico. This morning's mesoanalysis shows PWs of 1.25-1.6
inches (3-4 std dev above normal) covering much of region. This
moisture along with increasing large-scale ascent, provided by an
approaching upper trough, will support another day of widespread
showers and storms capable of producing moderate to heavy amounts.
Maintained a Slight Risk covering much of southern Arizona and a
small portion of southwestern New Mexico. Both the HREF and RRFS
neighborhood probabilities indicate locally heavy amounts
exceeding 2 inches are likely within this region, with some
potential for amounts over 3 inches, especially across parts of
southern Arizona.

...Eastern Southern Carolina and Southeastern North Carolina...

The initial low of what is expected to evolve into a two feature
system is forecast to linger along the coast in the vicinity of the
North and South Carolina border today. Deeper moisture will remain
as well, with many of the 00Z models, including the globals,
showing a notable signal for locally heavy amounts developing later
today. While instability will be limited, deep saturation through
the column, and tall, skinny CAPEs are expected to support very
efficient rains, promoting heavy amounts. Both the HREF and RRFS
showing high probabilities for additional amounts over 3 inches
today across parts of the region. These amounts may raise runoff
concerns, especially for those areas where significant rains have
already occurred. Therefore a Marginal Risk was introduced for
areas where the hi-res ensembles indicate the heaviest amounts are
most likely to fall.

...Northern Mid Atlantic to Southern New England Coasts...

North of its parent, a secondary, triple-point low is forecast to
develop near the northern Mid Atlantic coast. There remains some
model uncertainty regarding if and to what degree this low will
become the dominant surface feature. Despite the differences,
there is broad agreement that strong, low level easterly winds, in
combination with strong mid-to-upper level forcing, will support
widespread precipitation from the northern Mid Atlantic coastal
region to central New England, with heavy amounts expected along
the coast. These heavy rains may compound what are likely to be
poor ground conditions attributed to ongoing coastal flooding.

Pereira


Day 2
Valid 12Z Mon Oct 13 2025 - 12Z Tue Oct 14 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTHEASTERN ARIZONA, SOUTHWESTERN NEW MEXICO, AND SOUTHERN COLORADO...

...Southwest to the Central Rockies...

Lingering deep moisture over southern Arizona and New Mexico will
be drawn north ahead of an upper trough amplifying over California.
This moisture along with the broad-scale ascent afforded by the
upper trough will support one more day of showers and storms across
the Southwest, but this time shifting a bit further east while
extending north across New Mexico into the central Rockies. With
drier air working into southwestern Arizona, the potential for
heavy rain and the threat for flash flooding will become more
limited across that area. However, further to the north and east, a
Slight Risk was maintained along eastern portions of the Mogollon
Rim into southeastern Arizona and southwestern New Mexico. There
remains a notable signal for additional moderate to locally heavy
amounts across that area. Also remaining is a Slight Risk in a
portion of the San Juan Mountains, where models show deep
persistent southerly winds, along with favorable upper forcing,
supporting heavy totals as well.

...Northern and Central California....

Models remain in generally good agreement, showing an anonymously
deep upper developing and dropping south along the West Coast from
the Pacific Northwest to Northern California this period. Moisture
with this system will be relatively modest initially, but enough
to raise moisture anomalies to 1-2 std dev above normal along its
axis of strong onshore flow. This along with strong forcing may be
sufficient to produce locally heavy amounts, with isolated runoff
concerns, especially in the upslope regions of the coastal ranges
and the Sierra foothills below the snow line.

....Northeast...

Questions remain as to how the low developing along the Northeast
coast will continue to evolve, but most agree on at least a
localized threat for heavy rain spreading north from southern New
England up along the coast to areas perhaps as far north as coastal
Maine. Given the uncertainty, kept the Marginal Risk centered to
the area where the GEFS and ECENS both indicate that amounts
exceeding an inch are most likely.

Pereira


Day 3
Valid 12Z Tue Oct 14 2025 - 12Z Wed Oct 15 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL OVER PORTIONS OF
CENTRAL TO SOUTHERN CALIFORNIA, NEW MEXICO, AND WEST TEXAS...

...Central to Southern California...

A deep upper low will continue to dig south early in the period
before turning east across California into the Great Basin this
period. Before turning inland, this system will support an ongoing
threat for heavy precipitation, with the focus shifting south along
with its associated axis of deep onshore flow across Southern
California into the southern Sierra Nevada. A Marginal Risk was
drawn south along the Southern California Transverse Ranges, where
0.75-1 inch PWs interacting with favorable upper jet dynamics and
orographic ascent are expected to support rainfall amounts of 1-2
inches along the favored terrain. These amounts may produce
isolated runoff concerns, especially over vulnerable burn scar
areas. A Marginal Risk was also maintained further to the northeast
along the southern Sierra foothills, where similar amounts are
expected below the snowline.

...New Mexico and West Texas...

As drier air continues to spread east across Arizona into eastern
New Mexico, PWs anomalies will remain high across portions of
central New Mexico and West Texas where strengthening low level
easterly winds will add to the lingering moisture. With the
increase in moisture, the GFS shows PW anomalies remaining over 3
std dev above normal across much of the highlighted areas. This
along with daytime heating will support additional shower and
thunderstorm development, with some potential for locally heavy
amounts and isolated runoff concerns.

Pereira
$$
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FOUS30 KWBC 130754
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
354 AM EDT Mon Oct 13 2025

Day 1
Valid 12Z Mon Oct 13 2025 - 12Z Tue Oct 14 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTHEASTERN ARIZONA, SOUTHWESTERN NEW MEXICO, AND SOUTHERN COLORADO...

...Southwest to the Central Rockies...

Elevated moisture running between 2-4 deviations above normal will
remain situated across the Four Corners into the Central Rockies
down through the Southwest CONUS with roots persistent from the
tropical flux associated with now deceased tropical cyclone
Raymond. The persistence in the longwave pattern has allowed for a
continuous onslaught of heavy convective threats across the Desert
Southwest with a large amount of flash flood warnings tied to the
efficient rainfall processes exhibited given the supportive
atmospheric profile. For at least one more period, another round of
heavy precip will focus across portions of AZ/NM up into the San
Juans and adjacent Rockies of CO thanks to the flow actually
becoming even more meridional in-leiu of a buckling upper jet
pattern across the west coast stemming from a digging powerful
shortwave meandering down from the Pacific Northwest (More on this
setup below). As of now, there is a consistent signal in the hi-res
means for scattered heavy convective threats situated along the
eastern half of the Mogollon Rim into NM with a secondary maxima
situated over the San Juans where persistent upslope flow and mid-
level perturbations will enhance rainfall concerns within the
terrain for a third consecutive day.

00z HREF EAS probs for >1" are running high (>60%) for both the
areas mentioned above, plus >2" signals across the San Juans
maintain a strong 50-70% output meaning heavy rain prospects are
increasingly certain in the period. The one caveat to a higher
threat is the general lack of sufficient rates that would promote a
greater flash flood concern, especially one that carries more
significant impacts. Locally impactful outcomes are still plausible
considering some of the antecedent conditions leading into the
setup, so it's not out of the question some considerable flash
flood prospects could materialize in areas outlined in the SLGT
risk. Overall, this setup is conducive for at least scattered flash
flood potential leading to a general continuity of the SLGT from
previous forecasts with some adjustments based on the latest prob fields.

...California....

Current WV satellite and UA analysis indicates a powerful closed
ULL situated over the Olympics of Washington state with an
anticipated trajectory down the Pacific coast before it finally
loses latitude near Central CA before beginning to pivot inland.
During the forecast upper evolution, a strong south-southwest push
of Pacific moisture will favor an increase in regional PWAT
advection pressing inland across CA through the course of the D1.
The latitudinal push will allow for a persistent onshore component
within the coastal terrain from northwest CA down into the
Transverse Range of Southern CA towards the back end of the
forecast cycle. This will allow for 6-12 hr periods of heavy
rain potential within the confines of those coastal terrain
elements leading to isolated flash flood prospects as the setup
evolves. As of this time, the greatest threats for flash flooding
will be within those coastal terrain proxy's, however the inland
push of slightly anomalous moisture will also produce an element of
heavy rainfall in the Sierra Foothills, especially for the upslope
regions of the central and southern Sierra below 7000ft MSL. These
areas could see impacts from complex drainage within the steep
terrain situated against the higher elevations just east that will
be encountering the first true winter event of the season at the
same juncture. Rates will be relatively capped as MUCAPE fields are
generally forecast to be more benign compared to other instances
we've had in the past. The best MUCAPE signatures are actually
aligned with the Transverse Range and northern Peninsular Range of
southern CA, an area that is likely the most prone for flash flood
potential due to the litany of burn scar remnants present over the area.

Trends the past 12-24 hrs. now position the flow to be generally
orthogonal to the terrain those locations towards the end of the
forecast cycle, a setup conducive for persistent heavy rainfall
anchored over the same areas for longer periods of time. Despite
the lack of enhanced rates, enough instability and orographic
forcing could lead to rates exceeding 1"/hr at times, more than
sufficient for flash flood concerns to arise right near the final 6
hr. period in the D1. The previous forecast was relatively
unchanged north of the Transverse Range, but with the deeper
meridional inflection in the mean trough, the threat for flash
flooding across the southern CA terrain has sped up in time, thus a
MRGL extension into the Ranges northwest and north of Los Angeles
were implemented to reflect the latest trends. This will be a time
frame to monitor for any targeted upgrades if guidance allows.

Kleebauer


Day 2
Valid 12Z Tue Oct 14 2025 - 12Z Wed Oct 15 2025

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL OVER PORTIONS OF
SOUTHERN CALIFORNIA...

...Central to Southern California...

Our western disturbance will continue its progression slowly inland
with a steady south-southwesterly component situated over the
terrain of southern CA. Expect a continuance from the D1 to bleed
into the first half of D2 with heavy rainfall aligned within the
eastern Transverse Range and the northern Peninsular Range to the
north and northeast of Los Angeles. PWAT anomalies on the order of
1-2 deviations above normal are sufficient for a deep layer
moisture regime capable for heavy rainfall rates between 0.5-1"/hr
with a chance for a few stronger cores to exceed 1"/hr, a signal
more than capable of producing flash flooding in-of the area most
susceptible given the burn scar remnants positioned in the
Peninsular Range. Additional totals of 1-3" are forecast with
locally higher possible in those areas northeast of Los Angeles in
the terrain. Totals for the event will run between 1-4", plentiful
over a span of 12-24 hrs. to cause issues in what is a sensitive
locale for flash flooding and debris flow. The previous SLGT risk
was linked together and spans the eastern Transverse into the
northern Peninsular Range. MRGL risk is in place surrounding,
including an extension into parts of the Central Valley and
adjacent Sierra Foothills as locally heavy rainfall is still
forecast through the first 6-12 hrs. of the period which could spur
some isolated flash flood signals.

...New Mexico and West Texas...

Remnant elevated moisture across far west TX into NM within a
persistent axis of diffluent flow will yield a period of scattered thunderstorms over the two areas leading to isolated flash flood
concerns, mainly in urban zones and over the complex terrain
aligned from the Sacramento's up into the Sangre de Cristos. Totals
are not very appreciable at this juncture, but environmental
conditions still support some heavier rainfall prospects over areas
that will have seen a decent amount of rain leading in. Combination
of antecedent conditions and additional rainfall place the threat
inside the MRGL risk threshold leading to general continuity from
previous forecast.

Kleebauer


Day 3
Valid 12Z Wed Oct 15 2025 - 12Z Thu Oct 16 2025

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL OVER PORTIONS
OF THE CENTRAL AND SOUTHERN ROCKIES...

...Rockies...

Longwave pattern out west will continue to evolve with upstream
troughing pushing east-northeast leading to a final prospect of
isolated to scattered convection over the terrain of the central
and southern Rockies. A lot of the threat stems from RER
positioning with a broad upper jet aligned over the Mountain West
with an extension into the High Plains by the end of the forecast
cycle. The main areas of concern will likely be in those complex
terrain locations in-of the Sangre de Cristos, San Juans, and down
near the Sacramento's. These areas will all have either very wet
antecedent soil moisture that would promote easier run off
capabilities, or burn scar remnants that maintain a posture for
localized flash flood opportunities with any rates >0.5"/hr. This
is still feasible with PWATs remaining ~2 deviations above normal
in this zone when assessing the latest NAEFS output. A MRGL risk
remains in place over these areas of the central and southern
Rockies as a result.

Kleebauer
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