FOUS30 KWBC 140826
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
426 AM EDT Tue Apr 14 2026

Day 1
Valid 12Z Tue Apr 14 2026 - 12Z Wed Apr 15 2026

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS THE CENTRAL
L.P. OF MICHIGAN AND SOUTHEAST WISCONSIN...

...Great Lakes Region...

A Slight Risk for excessive rainfall remains in effect for portions
of the Great Lakes region. A shortwave/vorticity center lifting
out over the mean ridge in the Great Lakes region will drive
stronger confluence of the low level jet across Iowa to trigger another
round of strong to severe thunderstorms Tuesday evening. Overall
deep layer steering flow and fairly orthogonal ascent over boundary
should help to focus a similar west to east (WNW to ENE) oriented
axis of training thunderstorms. Upper-level dual jet couplet will
further enhance up-scale growth to a broader complex to maintain
through the overnight period. Most of the area remains at near or
above record spring rainfall and soils are fairly saturated, so
with cells capable of 1.5-2"/hr rates and localized totals of 2-3+"
suggest the placement of a Slight Risk of Excessive Rainfall
across portions of eastern WI and central MI (along and north of I-94).

...Pecos River Valley through Southern Plains into Ozark Plateau...

A steady stream of PW values of 1.25 to 1.5 inches will be
advecting northward through the Southern/Central Plains nearly
parallel to the dryline. This will be conducive for slow storm
motion with locally heavy rainfall. Consensus suggests 3 to 4
inches possible within the isolated cells. The Marginal Risk area
is connected to the area of concern over the Great Lakes and just
note the coverage will decrease northward along the dry-line.

Campbell/Gallina


Day 2
Valid 12Z Wed Apr 15 2026 - 12Z Thu Apr 16 2026

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM TEXAS TO
THE UPPER MIDWEST/GREAT LAKES REGION...

The surface to mid-level environment remains very similar to the
prior 3 days, with a stark dry line extending from the Pecos River
Valley across the Southern Plains into the Upper Mississippi
Valley. During this period the longwave trough will finally be
making progress toward the Central Plains albeit as it begins to
weaken and the deep layer moisture axis and instability shift
slightly eastward. Thunderstorms are expected to break out with
hourly rates pulsing up to 2 inches/hr. Some locations ahead or
along the frontal boundary may receive over 3 inches between the
Ozarks Plateau and northeast Texas.

Further north, the environment over the Midwest/Great Lakes region
will have notably less moisture and instability present then the
days prior, however additional rains will maintain an elevated
threat for localized flooding over the hydrologically
sensitive/saturated areas of the northern Great Lakes region. The
most favorable location for appreciable precipitation will be from
northeast Illinois to souther Michigan. The Marginal Risk area was
maintained and in spans from northeast Texas northward to
Wisconsin/Lower Michigan and east to western New Yorks and Pennsylvania.

Campbell/Gallina

Day 3
Valid 12Z Thu Apr 16 2026 - 12Z Fri Apr 17 2026

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

Campbell
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 150803
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
403 AM EDT Wed Apr 15 2026

Day 1
Valid 12Z Wed Apr 15 2026 - 12Z Thu Apr 16 2026

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR THE GREAT=20
LAKES AND NORTHERN OHIO VALLEY..

Showers and thunderstorms will continue to focus near the west-east
orientated frontal boundary draped across the Ohio Valley/Great
Lakes region into the Northeast as a weak surface low traverses the
boundary and intersects the abundant moisture and instability. Meanwhile,
the longwave trough will finally be making progress toward the=20
Central Plains and the deep layer moisture axis and instability=20
shifts slightly eastward. This setup will be conducive for periods
of heavy rainfall. Models are suggesting areal averages of 1 to 3
inches occurring with some overlap with rainfall footprint from
prior days. The Slight Risk remains in effect from northern=20
Illinois to souther Michigan and northwest Ohio to account for=20
uncertainty on storm track and the spread of 2 inch HREF 24 hr QPF=20 neighborhood probability.

...Eastern Oklahoma and the Ozarks...

Convection is expected to become more active during the afternoon
and track generally from the southwest to northeast ahead of the
approaching trough. Eastern Oklahoma into the Ozarks will be in=20
the right entrance of the jet streak, which will help provide lift.
At the surface, high PWATS and surface instability will once again
prime the atmosphere for hourly rainfall rates of an inch/hr. QPF=20
guidance does show a maximum of 1-2 inches across the region, but=20
model guidance shows little to no probability for accumulations=20
exceeding 2 inches. Therefore, a Marginal Risk is maintained for=20
the risk area. Additionally, the more flash flood prone Ozark=20
mountain range is relatively dry.

...Northeast...

Remnants of the storms across the Great Lakes may bring a round of
showers and storms in the morning, followed by another round of=20
heavier showers and thunderstorms in the afternoon. Model guidance=20
shows a corridor of 1-1.5 inches rainfall with embedded higher=20
amounts depending on the model. The relatively lower flash guidance
across western Pennsylvania and the more urban footprint of areas=20
such as Connecticut and New England also help confidence of=20
expanding the Marginal eastward.

Campbell/Wilder


Day 2
Valid 12Z Thu Apr 16 2026 - 12Z Fri Apr 17 2026

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

Campbell


Day 3
Valid 12Z Fri Apr 17 2026 - 12Z Sat Apr 18 2026

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR NORTHERN
MISSOURI, EASTERN IOWA AND NORTHWEST ILLINOIS...

A band of weakening showers and thunderstorms will pass through=20
the Ohio Valley with the lead shortwave trough. Meanwhile the long
wave trough approaching the Midwest will have better large scale=20
ascent and instability to yield better areal coverage of QPF with a
more focused swath of higher amounts across Missouri to the
Illinois/Wisconsin border. The previous Slight Risk area was
positioned more over Iowa and Wisconsin, however the latest trends
suggest a modest south/southeast adjustment to northern Missouri,
eastern Iowa, northwest Illinois and extreme southwest Wisconsin.=20
will be valid from northern Missouri to southwestern Wisconsin for=20

Campbell
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 160809
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
409 AM EDT Thu Apr 16 2026

Day 1
Valid 12Z Thu Apr 16 2026 - 12Z Fri Apr 17 2026

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

Campbell


Day 2
Valid 12Z Fri Apr 17 2026 - 12Z Sat Apr 18 2026

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF=20
THE MID-MISSISSIPPI VALLEY INTO THE SOUTHERN PLAINS...

A deep, positively-tilted longwave trough advancing into the Plains
will promote broad areas of ascent from the Southern Plains to the
Midwest. A well-defined axis of diffluence ahead of the mean=20
trough with several shortwaves rippling through the flow will=20
enhance an area of convective development within a strengthening=20
warm-sector environment positioned between a strong cold front over
the High Plains and a quickly advancing warm front migrating=20
poleward through the adjacent Mississippi and Ohio Valleys. This
environment will be rather favorable for a broad footprint for
heavy rainfall. There has been a persistent south/southwest trend
with the axis of highest QPF for several model cycles which now
focuses over northeast Oklahoma to north-central Missouri with
areal averages of 1-2 inches with isolated maximums nearing 3+
inches. The adjusted Slight Risk spans from northeast Oklahoma to
northern Illinois with the encompassing Marginal Risk from the
Oklahoma.Texas border northward to Wisconsin.

Campbell/Kleebauer


Day 3
Valid 12Z Sat Apr 18 2026 - 12Z Sun Apr 19 2026

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTH, LOWER MISSISSIPPI VALLEY AND TEXAS...

The frontal system described above will continue to advance
eastward with the trailing tail of the cold front dropping
south/southeast through Texas and the Lower Mississippi Valley.
Gulf moisture will be advecting northward into the Southern Plains
and pooling across Texas. PW values of 1.25-1.5 inches will be present
over much of eastern Texas and Louisiana during this period. Strong
convergence will lead to showers and thunderstorms focusing along
and ahead of the frontal boundary, especially for the later half of
the period. Areal average of 1 to 2 inches expected with hourly
rainfall rates greater than 1 inch/hr as well may lead to isolated
areas with flash flooding concerns. A Marginal Risk area is in
effect from South Texas to northern Mississippi.

Campbell
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 170746
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
346 AM EDT Fri Apr 17 2026

Day 1
Valid 12Z Fri Apr 17 2026 - 12Z Sat Apr 18 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM OKLAHOMA
THROUGH PORTIONS OF THE MIDWEST...

A strong cold front tracking southeast across the Plains will run
into a moist and unstable air mass driven by a robust low level jet
streaming north off the western Gulf and into the Great Lakes.
Meanwhile, a strengthening upper level jet will develop across
Texas and Oklahoma Friday night that will further enhance lift
across the Slight Risk region, particularly the southern part of
it. The result will be a series of waves of strong thunderstorms
that will feed on the influx of moisture and instability to allow
for frequent redevelopment and training as the entire complex of
storms pushes southeast. The strongest storms and most persistent
rainfall will occur over areas hard-hit in recent days with prior
heavy rainfall, so soils in areas from southern Oklahoma to western
Missouri are already near saturation and well above normal for soil
moisture content for this time of year. Urban areas from Kansas
City to Tulsa will be especially vulnerable should persistent heavy
rains set up over those metro areas. Meanwhile, a portion of the
Ozarks could also introduce a topographic factor to any flooding
potential. A higher-end Slight (25-40% chance of flash flooding)
is in effect from northwestern Oklahoma through central Missouri.

Meanwhile, further north into the Midwest, the storms are more
likely to organize into a single line of storms more quickly.
However, these areas have even more saturated soils due to more
recent rains. When added the urban factor in cities such as St.
Louis, Chicago, and Milwaukee, even a shortened period of heavy
rainfall could still result in widely scattered instances of flash
flooding. The Slight Risk in this area was expanded north up Lake
Michigan to Green Bay, but elsewhere remains little changed.

Wegman


Day 2
Valid 12Z Sat Apr 18 2026 - 12Z Sun Apr 19 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE GULF COAST AND LOWER MISSISSIPPI VALLEY...

A strong cold front sweeping south down the Plains will provide the
primary forcing for a line of strong thunderstorms to form as the
front uplifts a warm and moisture-laden air mass from the Gulf. Due
to close proximity to the Gulf, PWATs are likely to spike to
between 1.5 and 1.75 inches Saturday evening. This will support
thunderstorms capable of very heavy rainfall. The line will
generally be progressive, moving south. Further, the Marginal Risk
area is generally covering some of the highest FFG areas in the
country. Thus, the flash flooding threat is largely focused on the
urban factor in areas such as Houston, Beaumont, and Alexandria.
Most of the convective activity is expected at or after sunset, so
any flooding that occurs will be more dangerous.

Wegman


Day 3
Valid 12Z Sun Apr 19 2026 - 12Z Mon Apr 20 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR DEEP SOUTH
TEXAS...

An area of disturbed weather, partially from the remnants of a cold
front that swept across much of Texas on Saturday, will impact
portions of Deep South Texas Sunday into Sunday night. The air mass
will be characterized by summer-like amounts of moisture, with
PWATs exceeding 2 inches in a few areas, and over 1.75 inches
across much of Deep South Texas. This will support any showers and thunderstorms that form across the area to be capable of very
heavy rainfall. However, the forcing for this rainfall will be
lacking, resulting in only isolated to widely scattered showers and thunderstorms. Further, the FFGs in Deep South Texas are quite
high, so any storms, which should be slow-moving, would need to
train or remain over a single area for a while to produce flash
flooding. Thus, only isolated instances of flash flooding are expected.

Wegman
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 180658
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Sat Apr 18 2026

Day 1
Valid 12Z Sat Apr 18 2026 - 12Z Sun Apr 19 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE GULF COAST AND LOWER MISSISSIPPI VALLEY AS WELL AS FOR PORTIONS
OF THE MID-ATLANTIC...

...Gulf Coast and Lower Mississippi Valley...

A cold front sinking south across Texas on Saturday will run into
an increasingly moist and unstable air mass located along the Gulf
Coast Sunday afternoon. As the front lifts that air mass, rounds of
showers and thunderstorms are expected to form and roughly parallel
I-10 from near San Antonio east through southwestern Louisiana. The
potential for multiple rounds of heavy rain across urban areas,
particularly Houston, could result in isolated instances of flash
flooding. Recent dry weather across southeast Texas and especially
into Louisiana and southern Mississippi should work to limit the
flash flooding potential there, whereas across central Texas, soils
are a bit wetter from more recent heavy rainfall. Thus, FFGs
precipitously increase with eastward extent along I-10. The
inherited Marginal Risk was trimmed on the northern side, as the
most persistent thunderstorms are likely to focus further south
towards the Gulf Coast. The Marginal was expanded a bit west down
I-10 towards San Antonio due to the aforementioned more favorable
soil conditions.

...Mid-Atlantic...

A progressive line of thunderstorms associated with a fast-moving
cold front will sweep eastward across northern Pennsylvania and
western and central New York this afternoon and evening. The
Marginal was introduced primarily because preexisting moist soil
conditions across this region and the topography will both support
the development of isolated instances of flash flooding despite
less than impressive rainfall totals across this area. The line of
storms will traverse the Marginal Risk region at peak heating late
afternoon through the evening, which should allow the storms to
also be at their peak in strength.

Wegman


Day 2
Valid 12Z Sun Apr 19 2026 - 12Z Mon Apr 20 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTH TEXAS...

The cold front from Saturday night should be just off the coast
and into the Gulf Sunday morning, although a residual inverted
trough extending from the tail of this front is expected to linger
across South Texas much of the period. As the day progresses, weak
shortwave energy embedded within a shallow southern stream trough
will emerge from Mexico to produce modest ascent through divergence
and PVA, combining with convergence along the aforementioned
trough to create scattered showers and thunderstorms across the
region. Downstream of this feature, subtle ridging will halt the
progression of the surface trough, while additionally keeping PWs
pooled across South Texas, which is reflected by NAEFS ensemble
tables indicating that PWs will remain above the 90th percentile of
the CFSR climatology.

The overlap of this ascent into the moist column will manifest as
heavy rain producing convection, with both HREF and REFS indicating
a low end potential for 1"/hr rainfall rates. While the high-res
simulated reflectivity still features wide variation in coverage,
making confidence in the excessive rainfall potential a bit lower
than usual, storm motions within any of this convection will likely
be slow (0-6km mean winds of just 5-10 kts), so any of these heavy
rates could be sufficient to overcome the FFG. The greatest
potential may be along the immediate coast due to the overlap of
slower storms (pinned) and lower FFG, but anywhere these slow
storms develop, isolated instances of flash flooding could result.

Weiss


Day 3
Valid 12Z Mon Apr 20 2026 - 12Z Tue Apr 21 2026

...THERE IS A MARGINAL CHANCE OF EXCESSIVE RAINFALL ACROSS PARTS OF
NORTHERN CALIFORNIA AND ACROSS THE LOWER-MIDDLE TEXAS COAST TO THE
HILL COUNTRY...

...Northern California...

Deepening upper level low eventually closes off late in the weekend
off the northern CA coast. Afterwards, the guidance shows this
broad, deep low pinwheeling slowly eastward on day 3, thereby
allowing for a prolonged period of favorable forcing, i.e. upper diffluence/deep layer ascent and anomalous low-mid layer moisture
transport. The latest GEFS in fact indicates 850-700 mb moisture
flux peaking between 2-3 standard deviations above normal from the
Bay area into the northern CA coastal ranges and Sacramento Valley.
Due to the nature of the upper system (closed mid-upper low), this
will not be a typical AR event, per the 'weak' AR classification
from CW3E. However, Integrated water vapor transport (IVT) values
do peak around 500 Kg/m/s, while the guidance (GFS-ECMWF-NAM) does
indicate elevated CAPEs of 100-250 J/Kg. Areal average QPFs per the
guidance on Day 3 (12Z Mon-12Z Tue) support widespread 1-2"
rainfall totals, though higher-res members (including the RRFS) do
show isolated higher totals closer to 3". Given the potential for
at least 0.50"/hr rainfall rates on Day 3, the Marginal Risk area
was maintained (and expanded) to account for the possibility of
some excess runoff over burn scars.

...Lower-Middle Texas Coast to the Hill Country...

Guidance continues to show subtle/flat southern stream shortwave
traversing this area Mon-Mon night, which will likely become
convectively-aided from any MCV(s) emanating out of northeast
Mexico. Uptick in deep-layer forcing along with moisture pooling
from the western Gulf (PWs increasing to 1.7-1.8") and some, albeit
weak instability (MUCAPEs ~500 J/Kg) will lead to a more favorable
environment for widespread rainfall with embedded heavier cores. We
maintained the Marginal Risk area inherited from yesterday's Day 4
ERO, while expanding a little farther north to include parts of the
Hill Country based on the latest guidance trends (deterministic and probabilistic QPF). In addition, the latest ECMWF Extreme Forecast
Index (EFI) for QPF peaks between 0.6-0.7 during this event, with
a shift-of-tails close to 1 along the coast.

Hurley
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 190745
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
345 AM EDT Sun Apr 19 2026

Day 1
Valid 12Z Sun Apr 19 2026 - 12Z Mon Apr 20 2026

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

In coordination with CRP/Corpus Christi, TX and EWX/San Antonio, TX
forecast offices, the inherited Marginal Risk across Deep South
Texas was removed with this update. While there will be high
moisture content (PWATs around 1.75 inches) and slow moving cells
due to light steering winds across Deep South Texas, the lack of
instability and very high FFGs will effectively squelch any flash
flooding threat. MUCAPE values will struggle to exceed 300 J/kg
through the day, which is simply not enough instability to generate
the rain rates necessary to exceed the high FFGs.=20

Wegman


Day 2
Valid 12Z Mon Apr 20 2026 - 12Z Tue Apr 21 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA...

...Northern California...

A large upper level cutoff low located off the coast will drift
eastward into northern California on Monday. The cutoff low will
not have a connection to the tropics, which will limit both amount
of moisture and any instability that can be transported into
northern California. Despite that, as is typical of cutoff lows,
the movement will be slow, which could allow for an extended
duration of light to moderate rainfall. That rain will impact an=20
area that has burn scars, urban areas (Bay Area), and steep terrain
which favors localized flash flooding. Thus, the Marginal Risk is
left unchanged with this update.

...South Texas...

The inherited Marginal Risk over a portion of this area was
removed with this update, in coordination with CRP/Corpus Christi,
TX, EWX/San Antonio, TX, and HGX/Houston, TX forecast offices. As
on Day 1/Sunday, the limiting factor once again will be a true lack
of instability, with MUCAPE values again struggling to exceed a
couple hundred J/kg anywhere in Texas. Thus, despite above normal
atmospheric moisture, and below normal forward motions for any
cellular convection that does form, the high FFGs and limited
rainfall rates should continue to prevent any flash flood development.

Wegman


Day 3
Valid 12Z Tue Apr 21 2026 - 12Z Wed Apr 22 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CALIFORNIA AND SOUTHEAST TEXAS...

...California...

A cutoff large upper level low over the coast Tuesday morning will
progress east/inland through Tuesday night. This will direct the
southwesterly onshore flow further south and east across central
California. A pocket of instability with MUCAPE values as high as
500 J/kg may move into central California during the day Tuesday as
well. The primary forcing however will remain the steep slopes of
the Sierras, where the greatest rainfall rates and amounts are
expected. Due to the instability however, the more populous valley
locations may also see periods of heavier rains, including across
the Bay area and Sacramento. Burn scars and heavier rains into some
of the coastal ranges and western Transverse Ranges could also
result in localized flash flooding. Thus, the inherited Marginal
risk was expanded south down the coast to Santa Barbara, while the
Marginal in central California was left unchanged with this update.

...Southeast Texas...

The Marginal Risk across southeast Texas was adjusted a bit to the
northeast from inherited in keeping with the latest trends in the
guidance, suggesting increased potential for heavier rains into the
Houston area, and decreased potential around Corpus Christi. Unlike
both Sunday and Monday, by Tuesday there's better agreement that
the primary limiting factor, instability, will be less of a
limiting factor. MUCAPE values are expected to rise above 1,000
J/kg across much of the MRGL risk area. Somewhat more saturated
soils in the Houston area as a result of yesterday's rains could
also have some lingering effects into Tuesday. Thus, the inherited
Marginal was left largely unchanged with this update.

Wegman
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 200804
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
404 AM EDT Mon Apr 20 2026

Day 1
Valid 12Z Mon Apr 20 2026 - 12Z Tue Apr 21 2026

...THERE ARE MARGINAL RISKS FOR EXCESSIVE RAINFALL FOR PORTIONS OF
NORTHERN CALIFORNIA AND SOUTHCENTRAL TEXAS...

...Northern California...

A large upper level cutoff low located off the coast will drift
eastward into northern California today. The cutoff low will not
have a connection to the tropics, which will limit both amount of
moisture and any instability that can be transported into northern
California. Despite that, as is typical of cutoff lows, the
movement will be slow, which could allow for an extended duration
of light to moderate rainfall. That rain will impact an area that
has burn scars, urban areas (Bay Area), and steep terrain which
favors localized flash flooding. Thus, the Marginal Risk is left
unchanged with this update.

...Southcentral Texas...

A new Marginal Risk was reintroduced for a portion of Southcentral
Texas with this update in coordination with EWX/San Antonio, TX
forecast office. A subtle shortwave in the upper levels will add
forcing to an already highly moist environment with relatively slow
storm motions. Instability will be the primary limiting factor for
heavy rainfall rates, but the shortwave is expected to overcome
that instability a bit with the increased forcing. This solution is
depicted in several of the CAMs, which show a series of training
storms developing well after sundown, and tracking slowly eastward
across Southcentral Texas. Many of those CAMs highlight the storms
tracking right over the San Antonio metro area. The primary flash
flooding threat involves urban concerns in the San Antonio metro
Monday night.

Wegman


Day 2
Valid 12Z Tue Apr 21 2026 - 12Z Wed Apr 22 2026

...THERE ARE MARGINAL RISKS FOR EXCESSIVE RAINFALL FOR PORTIONS OF
CALIFORNIA AND SOUTHEAST TEXAS...

...California...

A cutoff large upper level low over the coast Tuesday morning will
progress east/inland through Tuesday night. This will direct the
southwesterly onshore flow further south and east across central
California. A pocket of instability with MUCAPE values as high as
500 J/kg may move into central California during the day Tuesday as
well. The primary forcing however will remain the steep slopes of
the Sierras, where the greatest rainfall rates and amounts are
expected. Due to the instability however, the more populous valley
locations may also see periods of heavier rains, including across
the Bay area and Sacramento. Burn scars and heavier rains into some
of the coastal ranges and western Transverse Ranges could also
result in localized flash flooding. The forecast remains on track
across California, and no changes were made. However, increases in
forecast rainfall along the Sierras in the Central Valley may
require a Slight Risk upgrade with future updates.

...Southeast Texas...

The Marginal Risk across southeast Texas remains unchanged with
this update. Onshore flow of deep Gulf moisture will advect across
southeast Texas along the periphery of a large area of high
pressure across the Southeast. MUCAPE values are expected to rise
above 1,000 J/kg across much of the MRGL risk area. Slow-moving and
training thunderstorms could cause isolated instances of flash
flooding, especially in urban areas such as Houston.

Wegman


Day 3
Valid 12Z Wed Apr 22 2026 - 12Z Thu Apr 23 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEAST TEXAS AND SOUTHWEST LOUISIANA...

Persistent onshore flow of deep Gulf moisture and instability will
continue into southeast Texas and southwest Louisiana on Wednesday.
This is a continuation of the moist, unstable flow off the Gulf
from prior days, just drifted a bit to the east. Instability across
this region continues to increase compared to prior days, with
areas of over 2,000 J/kg in MUCAPE. Showers and thunderstorms will
continue to move northwestward amidst the southeasterly flow off
the Gulf. Urban areas such as Houston and Beaumont will have a
higher threat of isolated flash flooding, which will occur where
the storms with the heaviest rainfall rates are most persistent.

Wegman
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 220757
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
357 AM EDT Wed Apr 22 2026

Day 1
Valid 12Z Wed Apr 22 2026 - 12Z Thu Apr 23 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEAST TEXAS AND SOUTHWESTERN LOUISIANA...

Steady southerly flow off the Gulf will continue to advect a plume
of Gulf moisture northward across the Marginal Risk area. The flow
will not be much to write home about, generally between 5-15 kts=20
at 850 mb. In addition to the rather weak advection the upper=20
levels will become decidedly less favorable for widespread rain=20
across the region as ridging and associated subsidence build in.=20
Thus, there is good agreement that any heavy rains will be=20
disorganized and widely scattered in nature, as compared with the=20
rains further west across Texas the past couple days. Urban=20
concerns remain a driving factor for maintaining the Marginal.
Guidance has shifted a bit to the south and west with the threat
for a few cells capable of heavy rains. This resulted in the
Marginal being shifted west along I-10, over an area that has been
hard-hit with heavy rains in recent days. Meanwhile portions of the
Piney Woods of far eastern Texas were removed as guidance has
suggested any more organized cells will be confined to around the
I-10 corridor. The westward shift resulted in small trimming in
south-central Louisiana as well. Should there be greater than
expected organization from Houston west along I-10, a targeted
Slight Risk may need to be considered due to the saturated soils
from yesterday's and prior days' rainfall.

Wegman


Day 2
Valid 12Z Thu Apr 23 2026 - 12Z Fri Apr 24 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM NORTHEASTERN
OKLAHOMA THROUGH THE ARROWHEAD OF MINNESOTA...

A strong but slow-moving low will lurk north of North Dakota in
southern Manitoba Thursday and Thursday night. The leading cold
front associated with this low has consequently also slowed down
its forward speed in much of the guidance. The result has been an
increase in forecasted rainfall that will occur ahead of that cold
front as it uplifts a moist and unstable air mass with a 30-50 kt
LLJ. Since the front has slowed down, there's more time for
moisture to advect north with the LLJ into Iowa, Minnesota, and
Wisconsin. While portions of Minnesota and Wisconsin were hard hit
with heavy rains last week, there has been sufficient time for the
soils to dry out some and for the rivers to drain that rainfall.
Thus, conditions are at or even a bit below normal for soil
moisture. Despite that, potential for fast-moving but training
storms could still result in some "stripes" of heavier rainfall
that could cause isolated flash flooding, especially if urban
centers such as the Twin Cities are included. The inherited
Marginal was shifted west but expanded well to the north to include
some of these more vulnerable areas of Minnesota and Wisconsin with
this update. The good news is further south across Kansas and
Missouri, the forcing now doesn't look like it will be quite as
strong as the forecast looked 24 hours ago. Thus, while a Slight
Risk upgrade was considered for along the KS/MO border south of
Kansas City yesterday, confidence has increased that the current
Marginal Risk for that area will suffice.

Wegman


Day 3
Valid 12Z Fri Apr 24 2026 - 12Z Sat Apr 25 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE MIDDLE AND LOWER MISSISSIPPI VALLEY...

A slow-moving cold front will run into increasing Gulf moisture and
instability across the Middle and Lower Mississippi Valley on
Friday. Clusters of showers and thunderstorms will develop along
the front in northwestern portions of the Marginal across Arkansas
and southeastern Missouri with peak heating Friday afternoon. Those
storms will gradually progress south and east, with the potential
for localized training of stronger cells embedded within these
clusters of storms. Almost all of the Marginal Risk area is in an
area with extremely dry soils. Depending on the soil type, this
could make some of the soils (clays) start out the rainfall event
in a very hydrophobic state, which would support rapid runoff.
However, for most, all but the heaviest rains will be very
beneficial for this parched area of the country. Urban areas, areas
with hydrophobic soils, and poor-drainage areas will be at the
greatest risk for isolated instances of flash flooding. Smaller=20
drainage basins and the portions of Arkansas with the Ozarks=20
topographically confining any potential runoff to steep valleys
will also be at a locally higher risk for flash flooding.

Wegman
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 230746
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
346 AM EDT Thu Apr 23 2026

Day 1
Valid 12Z Thu Apr 23 2026 - 12Z Fri Apr 24 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN THE CENTRAL
PLAINS AND UPPER MIDWEST...

Convection is expected to blossom this afternoon along and ahead of
a cold front in the Central U.S. The warm sector ahead of the front
should be characterized by an overlap of moderate instability (1000
to 2000 j/kg MLCAPE) and anomalously high moisture content (1.0 to
1.5 inch PWATs; near or above the 90th percentile for late April).
The combination of instability and moisture should support heavy
rain rates in organized convection in excess of 1 inch per hour at
times. The main limiting factor for higher rainfall totals over the
entire forecast period, and any impacts from flash flooding, should
be a lack of persistence to the high rain rates in a given spot.

From the I-70 corridor to the north, lines of thunderstorms are
expected to be relatively narrow and steadily progress, given the
deep layer shear vectors will be oriented closer to perpendicular
with the cold front. Therefore, despite some pockets of lower flash
flood guidance (around or just under 2 inches in 3 hours), and
recent wet pattern in parts of the region, the heaviest rain rates
should not last very long and the flash flood risk is expected to
remain isolated. Furthermore, instability diminishes rapidly around
sunset, so rain intensity should drop off within about 6 hours of
convective initiation. It should be noted this assessment does not
necessarily apply to other flooding risks in the region: ongoing
mainstem river flooding, or potential for rain and snowmelt
flooding in the Upper Peninsula of Michigan. For more details on
those flooding hazards, refer to the National Water Center.

Further south, the pattern will be more supportive of backbuilding
and training convection, especially this evening and overnight from
southeast Kansas into northeast Oklahoma and the Ozark region of
southwest Missouri and northwest Arkansas. As the low level jet
veers and an upstream instability maximum persists in eastern
Oklahoma, hi-res models uniformly show a band of thunderstorms
becoming increasingly east-west oriented, more parallel to the deep
layer shear vector. Nevertheless, they all also show steady
progression to the southeast with some cold pool development, and a
lack of rainfall maxima in excess of 3 inches. Therefore, the risk
of flash flooding is currently expected to be isolated, but the
situation will be monitored in case a targeted Slight Risk is
needed later today.

Lamers


Day 2
Valid 12Z Fri Apr 24 2026 - 12Z Sat Apr 25 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN THE MID SOUTH...

A convective cluster or backbuilding convective line may be ongoing
on Friday morning -- most likely across northern Arkansas based on
00Z HREF EAS probabilities -- with the potential for additional
convective clusters to develop through the day across the region.
Updated WPC QPF places the heaviest rainfall across Arkansas,
northern Mississippi, and far northern Louisiana, and this is where
the Marginal Risk area was re-centered. There is some uncertainty
on where the heaviest rain will fall, as it should be tied in some
way to convective outflow from morning and early afternoon
activity. The warm sector to the south and southeast of that should
have a combination of moderate instability and precipitable water
close to 1.5 inches (around the 90th percentile for late April).
That sort of environment would support rain rates of 1 to 2 inches
per hour in organized convection, which could lead to isolated
flash flooding where backbuilding and training occurs.

Lamers


Day 3
Valid 12Z Sat Apr 25 2026 - 12Z Sun Apr 26 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN SOUTHEAST
KANSAS, SOUTHWEST MISSOURI, EASTERN OKLAHOMA, AND WESTERN ARKANSAS...

Available deep moisture in the southern Plains on Saturday should
be lower than prior days across the region, with model forecast
soundings indicating the potential for dry air from 800-600mb
associated with an elevated mixed layer. This would likely restrict
any excessive rainfall and flash flooding concerns to the isolated
variety. Nevertheless, strong instability and vertical wind shear
should support supercells evolving into convective lines. There is
not a consistent signal for concentrated areas of heavy rain, but
with the expected convective modes, localized areas of longer heavy
rain duration are possible via storm mergers and some upshear cell
development. Any corridors of heavy rain on Thursday or Friday
could also locally increase soil moisture and vulnerability to
another round of heavy rain. Therefore, the Marginal Risk was
maintained for Saturday and Saturday Night.

Lamers
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 240750
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
350 AM EDT Fri Apr 24 2026

Day 1
Valid 12Z Fri Apr 24 2026 - 12Z Sat Apr 25 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN THE MID SOUTH...

A convective line that had stalled over northern Oklahoma between
02Z and 06Z has recently shown signs of slow forward progress. This
increases confidence in the general evolution depicted in the 00Z
hi-res model guidance suite, which shows the line reaching northern
Arkansas and east-central Oklahoma by the start of the forecast
period at 12Z Friday, and continuing southeast through much of
central and eastern Arkansas through the daytime hours.

The end result should be an increasingly stable air mass and
widespread cloud cover over those same portions of Arkansas, and=20
adjacent southern Missouri and western Tennessee, associated with=20
gradually decaying convection, a cold pool and surface meso-high.=20
For these reasons, and trends to the southwest with the heaviest=20 precipitation in both hi-res and AI guidance, the Marginal Risk has
been shifted likewise. A reinvigoration of convection in the=20
afternoon and evening is most likely on the upshear flank of the=20
cold pool with west-southwesterly low level inflow and an upstream=20
reservoir of strong instability. The potential exists for periods=20
of training convection along and near the existing outflow boundary
(likely on the order of 1-3 hours), which may provide=20
opportunities for localized corridors of heavy rainfall with 1-2=20
inch per hour rain rates, and resulting flash flooding. The precise
placement remains somewhat uncertain, so the Marginal Risk remains
relatively broad to account for a variety of scenarios. In
particular, the risk area was fanned out a bit more to the north
and west than deterministic WPC QPF would imply, because of the
relatively slow pace of the ongoing convection and the very common
northeast placement bias in this sort of mesoscale setup respectively.

Lamers


Day 2
Valid 12Z Sat Apr 25 2026 - 12Z Sun Apr 26 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE ARKLATEX
REGION INTO EASTERN OKLAHOMA AND SOUTHEAST KANSAS...

It seems likely that scattered thunderstorms will develop on
Saturday afternoon in a corridor of strong instability across the
Southern Plains. However, there remains considerable uncertainty as
to the position of surface boundaries and the northward extent of
the strongest instability. Despite model guidance depicting a
variety of mesoscale scenarios, most models do show organized
convective clusters pushing southeast along the 1000-500mb
thickness gradient into the evening and overnight hours. This
motion could allow for some training and areas of locally heavy
rainfall; the strong instability and PWs of 1.2 to 1.5 inches would
support 1-2 inch per hour rain rates. If those rain rates can be
sustained for a couple hours, localized flash flooding would be
possible. For now the Marginal Risk was maintained as model
guidance does not really show any extended duration of training at
this point, and there is not enough model agreement to identify a
preferred corridor for heavy rainfall.

Lamers


Day 3
Valid 12Z Sun Apr 26 2026 - 12Z Mon Apr 27 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL IN THE CENTRAL
PLAINS AND OZARKS...

Strong cyclogenesis in the central Plains on Sunday will facilitate
significant northward moisture transport and a more expansive area
of thunderstorm activity stretching from the Dakotas south toward
Arkansas. The stronger signal for heavy rain exists further north
where stronger synoptic forcing and mid-upper level height falls
will be focused. However, instability is expected to be more
limited in those areas. Nevertheless, the combination of moderate
instability with PWs exceeding 1 inch and potential for more
persistence of rain and thunderstorms could yield localized flash
flooding. Further south, stronger instability could support higher
rain rates, but weaker forcing overall may keep convection
scattered and reduce opportunities for training and focused
corridors of heavy rainfall. Some portions of Kansas, Missouri,
Oklahoma, and Arkansas will likely have experienced substantial
rainfall in the preceding several days, and so may be more prone to
runoff issues if organized thunderstorms are more persistent. The
expected tradeoffs between convective coverage and available
instability, with respect to the overall flash flood threat, only
merit a broad Marginal Risk at this time.

Lamers
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 270750
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
350 AM EDT Mon Apr 27 2026

Day 1
Valid 12Z Mon Apr 27 2026 - 12Z Tue Apr 28 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE MIDWEST...

Multiple rounds of convection are expected today ahead of a cold
front extending from an anomalously deep spring low. Significant
northward moisture transport will result in a plume of PWs above 1
inch as far north as Lake Superior, and above 1.5 inches as far
north as Chicago. Along the entire length of the cold front, these
values will generally approach the 99th percentile for late April
and, combined with moderate to strong instability, should support
hourly rain rates in the 1 to 2 inch range. A limiting factor for
flash flooding will be the dominant convective mode -- very likely
to be relatively narrow squall lines, forced by a steadily
advancing cold front, that will limit the overall duration of the
heavy rain rates.

However, an area from northern and central Missouri, into much of
Illinois and Indiana, will have a greater potential for training
convection. This will be due to a significant upstream complex of
thunderstorms over northeast Kansas as of 07Z, which should shift
east over the remainder of the morning. The orientation of the
convective line is closer to parallel with the deep layer shear
vector, which will favor training over northern Missouri at the
start of the period. Eventually, this activity may produce an
outflow boundary oriented in a west-east fashion that would focus
subsequent convective development in a more favorable configuration
for additional training. The broad Slight Risk was maintained and
adjusted to better fit the latest guidance where probabilities of 1
inch per hour rain rates are highest.

Further south, a Marginal Risk was extended from Arkansas and
Tennessee southwest into central Texas to account for a conditional
threat of localized heavy rainfall and flash flooding. The
environment in these areas will be characterized by strong
instability (CAPE in excess of 3000 j/kg) and abundant deep
moisture (PW between 1.5 and 1.8 inches). The QPF signal in
guidance is inconsistent, but enough to indicate a threat for
isolated to scattered thunderstorms, primarily in the afternoon and
evening. The combination of the aforementioned instability with
strong deep layer shear could lead to a few slow-moving
supercells, which has been a theme in recent days. It is a classic
conditional threat -- while much of this region further south along
the front could remain dry, any storms that become organized and
rooted in the very unstable boundary layer could produce localized
very heavy rainfall.

Lamers


Day 2
Valid 12Z Tue Apr 28 2026 - 12Z Wed Apr 29 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE ARKLATEX
INTO THE MID SOUTH...

A favorable environment will exist for numerous organized
thunderstorms over the southern U.S. on Tuesday, with a broad warm
sector containing very strong instability (CAPE over 3000 j/kg),
deep moisture (PW climbing into the 1.6 to 2.0 inch range), and
strong deep layer shear (0-6km bulk shear 40-60 knots). In that
sort of environment, rain rates should reach 2 inches per hour. The
open question is what sort of mesoscale boundaries may exist to
focus convective development, and whether or not some of these will
be oriented in a west-east fashion (parallel to the bulk shear
vectors). Any prominent boundaries that are favorably oriented
could easily focus a corridor of significant rainfall and flash
flooding in this sort of environment. However, an equally plausible
scenario would be more scattered clusters and lines of
thunderstorms that can produce localized heavy rainfall and flash
flooding, but fail to focus the convection in a way that leads to
more significant totals. For now, it seems reasonable to maintain
the broad Slight Risk and wait for greater confidence in the
mesoscale details.

Lamers


Day 3
Valid 12Z Wed Apr 29 2026 - 12Z Thu Apr 30 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM CENTRAL AND
SOUTHEAST TEXAS TO THE CENTRAL GULF COAST...

The threat of excessive rainfall and flash flooding seems to be
increasing in the most recent set of model guidance, due to a
continuation of strong instability and the arrival of a plume of
unusual amounts of mid-level moisture. Backward trajectory
analysis indicates that moisture around 3km above the surface
originated in the tropical central Pacific, advected into the
southern U.S. by an anomalously strong subtropical jet (300mb winds
around 60+ knots) extending about 6000 mi. from the Marshall
Islands, to just south of Hawaii, all the way to Texas. This should
push PW values over the whole region above 1.7 inches, and above 2
inches in portions of Texas, which is quite unusual. For instance,
a 2+ inch PW has only been observed on an upper air sounding at
Corpus Christi 3 times prior to May 1st (36 year period of record;
since 1990). Although model QPF is not exceptionally high at this
point, that may largely be a function of a lack of high-res
guidance from convection-allowing models. The environment (when
also considering strong bulk shear to around 50 knots) would favor
organized thunderstorms with very high rain rates, potentially in
excess of 2 inches per hour. Given that the previous outlook had
probabilities below 5 percent, the main change with this update is
to introduce a Marginal Risk, but a further upgrade may be
required, especially across parts of Texas.

Lamers
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 280808
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
408 AM EDT Tue Apr 28 2026

Day 1
Valid 12Z Tue Apr 28 2026 - 12Z Wed Apr 29 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM THE ARKLATEX
REGION INTO THE MID SOUTH...

A favorable environment will exist for numerous organized
thunderstorms over the southern U.S. today and tonight. Outflow
from steadily advancing squall lines over the Tennessee Valley
should provide a more distinct focus for renewed convective
development over the forecast period. The boundary is likely to be
oriented west-east, essentially parallel to 40-50 knot bulk shear
vectors. Although the air mass north of the boundary may modify
with time, it should still provide low-level convergence and a
contrast in instability. South of the boundary, the warm sector
will have very strong instability (CAPE over 3000 j/kg) and deep
moisture (PW approaching 2 inches; above the 99th percentile for
late April). This parameter space is very supportive of high rain
rates, potentially in excess of 2 inches per hour in the most
intense and organized thunderstorms.

If anything, recent hi-res model runs (06Z HRRR, 00Z RRFS in
particular) have focused the heavy rainfall signal even more into a
corridor approximately 100 miles wide, with 2-4 inch totals and
localized maxima even higher. This is consistent with the expected
pattern described above, with repeated rounds of thunderstorms
along a distinct mesoscale boundary. The main change with this
outlook was to narrow the Slight Risk a bit, especially by trimming
from the stable (northern) periphery well into the stable side of
the mesoscale boundary. It could potentially be focused a bit more,
and that will be a consideration later today. A mitigating factor
for flash flood impacts could be the severe to extreme drought
conditions in place across much of the Slight Risk area. With rain
rates potentially in excess of 2 inches per hour, and heavy rain
sustained for several hours in some cases, drought conditions may
not necessarily prevent impacts but could lead to more isolated
instances of flash flooding. This is still consistent with the
Slight Risk definition. Flash flood guidance factors in current
ground and streamflow conditions, and HREF and REFS probabilities
still show about a 15-30 percent chance of exceeding FFG despite
the overall dry antecedent setup.

Lamers


Day 2
Valid 12Z Wed Apr 29 2026 - 12Z Thu Apr 30 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM CENTRAL AND
SOUTHEAST TEXAS TO THE CENTRAL GULF COAST...

The outlook for Day 2 has remained mostly unchanged, with a
Marginal Risk in a corridor from Texas through Alabama along the
western and central Gulf Coast. A threat of excessive rainfall and
flash flooding is expected, due to a continuation of strong
instability, and the arrival of a plume of unusual amounts of mid-
level moisture. Backward trajectory analysis indicates moisture
around 3km above the surface can be traced along an anomalously
strong subtropical jet extending back into the tropical central
Pacific Ocean. This should push PW values over the risk area above
1.7 inches, and above 2 inches in portions of Texas, which is quite
unusual for April. Given this, it's possible an upgrade to Slight
Risk may be needed in future outlook updates. However, hi-res
guidance is just coming into view. While the extended HRRR and RRFS
do both show rain rates in this environment reaching (and even
exceeding, in some cases) 2 inches per hour, confidence is not high
on placement of greater concentrations of convection. Additionally,
there doesn't seem to be much signal for backbuilding and training,
except perhaps via cell mergers, which could lead to more limited
duration of heavy rain. Therefore, the risk level was held at
Marginal for now for the entire region.

Lamers


Day 3
Valid 12Z Thu Apr 30 2026 - 12Z Fri May 01 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN CENTRAL TEXAS...

Increasing mid-upper level height falls over New Mexico and Texas,
due to a strong shortwave pushing through northern Mexico, should
lead to a low-level mass field response with increasing south to
southeast inflow across southern and central Texas. That will also
lead to a gradual uptick in low-level convergence between the
developing low-level jet, and an easterly cool conveyor belt to
the north, in a more stable region from Oklahoma into northwest
Texas. The result should be more numerous thunderstorms over the
course of the Day 3 period, particularly by Thursday Night. Deep
moisture will remain firmly in place, although the instability
should shift to a narrower CAPE profile with lower equilibrium
levels. That trend, in combination with PWs of 1.5 to 1.8 inches,
should support increasingly efficient, warm rain processes in
convective bands.

Furthermore, some training of the lower-topped convective bands may
occur. With stronger instability over South Texas, the Rio Grande
Valley, and far northeast Mexico, and steadily increasing forcing
from the approaching wave upstream, persistent new convective
growth upstream of convective bands is plausible.

Putting all these factors together, a Slight Risk was introduced
over Central Texas. This was placed where drought conditions either
do not exist or are much lower on the scale; that also happens to
be where some ensemble QPF signal is strongest. It's possible the
Slight Risk may trend southeast with time as AI guidance is
positioned on the southeast flank of the guidance envelope, and
would seem to be a logical corrective to the usual bias of QPF
maxima placed too far in the direction of a stable air mass,
especially with 2-3 days of lead time.

Lamers
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 010838
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
438 AM EDT Fri May 1 2026

Day 1
Valid 12Z Fri May 01 2026 - 12Z Sat May 02 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL IN CENTRAL AND
SOUTHEAST TEXAS EASTWARD ALONG THE CENTRAL GULF COAST...

Once again...minor reshaping of the Marginal and Slight Risk areas
were made to reflect small adjustments made in the WPC
deterministic QPF and the suite of 01/00Z global and CAM guidance. The
axis of the heaviest rainfall still forecast to span from eastern
Texas to eastern Louisiana and southern Mississippi where the best
moisture convergence and instability will be present. Recent rains
across the western an central Gulf states have increased soil
saturation, lessening the amount of additional rainfall required
for areas of flash flooding. Hourly rates of 1 to 3 inches/hr to
streak from eastern Texas to eastern Louisiana.

The overall evolution aloft coupled with a broad axis of
formidable moisture anomalies and instability should lead to an
axis of heavy rainfall across the Southern Plains from Texas over
through the Lower Mississippi Valley today into early Saturday
morning. A quasi-stationary front will orient itself across south-
central TX down to around the Gulf coast as a wave of low pressure
rides along the boundary. With precipitable water values forecast
to be 1.7 inches to 2.1 inches (in the 95th percentile or higher
for this time of year)...efficient warm rain processes can result
in torrential downpours with resulting flash flooding especially in
light of the upper divergence tied to the mid- and upper level
wave making its way through the southern Great Basin early this
morning. Thus there is little overall change to the forecast
reasoning for a high-end Slight risk area from parts of Texas into
Louisiana embedded within the broader Slight Risk area.

Farther east...the Slight risk area tapers off into a Marginal Risk
area where rainfall rates and amounts still have the potential to
result in flash flooding but where ingredients are not as well
aligned. The question in dry/drought areas always comes down to
rates and resulting amounts (whether it is from training or repeat
rounds). Thinking here rates may not be enough alone (with PW's
generally < 1.75-ish) but some potential for training prior to
frontal passage. The 01/00Z HREF neighborhood probs for 1-hr amts
at 1 in and 2 in thresholds focused generally along the LA/MS coast
(admittedly sub SLGT). The RRFS..which has a tendency to be
overconfident with probs and overly expansive...seemed to show its
bias on its 30/18Z run but focused pretty much along the same axis.
There remained some question on the latitude of the
axis...considering the latest UFVS verified machine learning
guidance focused a bit north of the HREF/RRFS axis closer to the
support offered by an upper jet streak.

Bann


Day 2
Valid 12Z Sat May 02 2026 - 12Z Sun May 03 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHEAST U.S....

A progressive upper trough is expected to help focus and sustain
showers and thunderstorms across portions of the Southeast United
States on Saturday into the early morning hours of Sunday. More importantly...the trough should result in any convection moving
with minimal risk of back-building or training. The setup promotes
a relatively favorable environment suitable for heavy rainfall
with the stronger cell cores capable of producing rainfall rates
between 1-2"/hr in a region where Flash Flood Guidance values
remain high. There was enough of a signal for the possibility of
some urban flooding to warrant keeping a previously-issued Marginal
Risk in place with minimal amount of changes needed.

Bann


Day 3
Valid 12Z Sun May 03 2026 - 12Z Mon May 04 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THEm SOUTHEAST FLORIDA PENINSULA ON SUNDAY...

A cold front associated with an area of low moving northeastward
off the eastern US seaboard will be draped across the central
portion of the Florida peninsula on Sunday...with the front
separating an airmass with precipitable water values at or
somewhat less than 0.5 inches in the panhandle and adjacent
portions of the peninsula to values in the 1.75 inch to 2.00 inch
over the southern half of the peninsula for much of Sunday and
Sunday evening. Mid- and upper-level shortwave energy embedded
within fast flow aloft will help focus and sustain thunderstorms
that could produce 1.5 to 2.5 inch per hour along and south of the
boundary. There remained enough of a signal for the potential of
some urban flooding across the larger urban areas so opted to keep
with the Marginal Risk area due to the high flash flood guidance.
Even if the QPF remains similar in future cycles...where/how much
rain falls in Days 1 and 2 will affect the flash flood guidance as
Day 3 makes its way towards becoming a Day 1 outlook.
Regardless...downpours and localized multiple-inch rainfall amounts
in the major cities is more likely to have flood- related problems
in either scenario.

Bann
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 030825
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
425 AM EDT Sun May 3 2026

Day 1
Valid 12Z Sun May 03 2026 - 12Z Mon May 04 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHEAST FLORIDA PENINSULA...

Just enough of a signal in the 03/00Z CAMS to maintain the Marginal
Risk area. The focus will be over the urban southeast coast as a
front advances into a region of deeper moisture and where CAPE
tends to be under 1000 J per kg. The 03/00Z HREF does depict a
low-end neighborhood probability of FFGs being exceeded over the
southern tip of the Florida peninsula in the 03/21Z to 04/00Z
period but the stronger signals in the guidance is for heavier
rainfall to be hugging the coast or remaining just off-shore. It
was noted that over the past couple of days...numerical models have
been cutting back the amount of moisture in the lowest layers which

Bann


Day 2
Valid 12Z Mon May 04 2026 - 12Z Tue May 05 2026

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

Bann


Day 3
Valid 12Z Tue May 05 2026 - 12Z Wed May 06 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MID MISSISSIPPI VALLEY INTO THE OHIO VALLEY...

Deep layer southwesterly flow leading into the start of the period
will be drawing moisture into parts of the Plains and then
downstream toward the Great Lakes and the Ohio Valley. As a trough
amplifies over the central part of North America and a jet streak
forms over the Southwest US and approaches the Plains...the chance
for showers and thunderstorms increases along and ahead of a
develops surface front. With precipitable water values of 1.75 to
1.9 inches embedded within a broader 1.5 to 1.75 area...which was
pushing two standardized anomalies greater than climatology for
this time of year--locally heavy rainfall and the associated risk
of localized flooding from late Tuesday afternoon into early
Wednesday is possible.

Bann
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 040826
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
426 AM EDT Mon May 4 2026

Day 1
Valid 12Z Mon May 04 2026 - 12Z Tue May 05 2026

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

Bann


Day 2
Valid 12Z Tue May 05 2026 - 12Z Wed May 06 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MID MISSISSIPPI VALLEY INTO THE OHIO VALLEY...

Deep layer southwesterly flow leading into the start of the period
will be drawing moisture into parts of the Plains and then=20
downstream toward the Great Lakes and the Ohio Valley. That large=20
scale picture has changed little but subtle run to run difference=20
in the global models and convective allowing models continues to=20
result in minor adjustments to the ERO. A mid- and upper-level=20
trough will be amplifying over the central part of North America=20
and a jet streak forms over the Southwest US and approaches the=20
Plains...the chance for showers and thunderstorms increases along=20
and ahead of a develops surface front. With precipitable water=20
values of 1.75 to 1.9 inches embedded within a broader where=20
precipitable water values of 1.5 to 1.75 are going to be more=20
common...areal average rainfall is expected to be on the order of 1
to 1.25 inches. In general this will be beneficial rain. However=20
there may be isolated areas where rain rates lead to local flash=20
flooding. There was spread between model members with the ARW core
favoring a western solution while models with an NMM core favored
areas farther east. Given the synoptic pattern and with the support
of the global models...the ERO was kept in general along and east
of the Mississippi River.

Bann


Day 3
Valid 12Z Wed May 06 2026 - 12Z Thu May 07 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE INTERIOR SOUTHEAST UNITED STATES...

Maintained a Slight Risk of excessive rainfall introduced by the
WPC Medium Range desk as shortwave energy drops out of Canada and
across much of the central and eastern United States. The coverage
and rainfall intensity should be increasing on Wednesday as the
best dynamics and the best Gulf moisture coverage with a frontal
boundary over the interior portion of the Southeast US.=20
Deterministic QPF tends to cluster in the 1.5 to 3 inch amounts=20
across part of the Tennessee Valley into the southern Appalachians
from Wednesday into early Thursday due to the presence of surface=20
dewpoints close to 70 degrees getting drawn northward from the=20
Gulf. Whether or not the convection evolves into line will affect=20
the amount of rainfall and any associated risk of flash flooding.

Bann
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 050827
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
427 AM EDT Tue May 5 2026

Day 1
Valid 12Z Tue May 05 2026 - 12Z Wed May 06 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MID MISSISSIPPI VALLEY INTO THE OHIO VALLEY...

Deep layer southwesterly flow had drawn Gulf moisture into parts
of the Plains and then downstream toward the Great Lakes and the
Ohio Valley. The resulting showers and thunderstorms today will be
able to tap into an atmosphere that generally has 1.5 inch
precipitable water or greater extending as far north as Ohio by the
overnight hours. The southeastward adjustment of the Marginal Risk
area still looks good and spans the placement of the 2 inch
contour shown by a handful of ARW-core and NMM-core ensemble
members. So few changes were needed and were not made due to a
fundamental shift in forecast reasoning.

Bann


Day 2
Valid 12Z Wed May 06 2026 - 12Z Thu May 07 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE INTERIOR SOUTHEAST UNITED STATES...

Maintained the slight southward shift of the previously issued Slight
Risk area introduced a couple of days ago. The coverage and
rainfall intensity should be increasing on Wednesday as a large
scale trough over the northern Plains continues to amplify and
result in a 140 kt to 160 kt upper level jet over the Tennessee
Valley during the latter part of the period. The resulting upper
divergence, steepening mid-level lapse rates and increasing
moisture and instability should result in convection capable of
producing heavy rainfall rates and embedded areas of rainfall
amounts of 3 to 5 inches as suggested by the latest run of the
RRFS. There is a fairly wide spread in the north/south placement of
that heavier axis. As a result...the Slight area was expanded
somewhat and tended to cover the greatest overlap of higher QPF and
exceedance probabilities. Thinking is that there are some
probabilities supportive of a higher-end slight risk embedded
within the broader Slight. The continued amplification of the upper
trough should keep the convection moving southward with time
during the overnight hours.

Bann


Day 3
Valid 12Z Thu May 07 2026 - 12Z Fri May 08 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE GULF COAST REGION TO THE SOUTHEASTERN UNITED STATES...

Showers and thunderstorms along and ahead of a surface cold front
will be lingering into Thursday from parts of the Gulf coast region northeastward into parts of Georgia and South Carolina. At this point...rainfall rates look to be decreasing as the better upper
level dynamics pull off to the northeast and low level flow becomes
directed along...rather than normal...to the front. Maintained a
Marginal Risk area where there could be overlap with areas somewhat
higher soil moisture content from recent rainfall. Overall the
rainfall looks to be more beneficial than not.

Bann
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 101800
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
200 PM EDT Sun May 10 2026

Day 1
Valid 16Z Sun May 10 2026 - 12Z Mon May 11 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
CENTRAL AND NORTH TEXAS...

...16Z Update...

The Slight Risk area was expanded a bit with this update, mostly
towards the south but also to include the rest of the DFW
Metroplex. Clusters of storms are expected to develop this
afternoon, likely as a continuation of the showers and storms
ongoing currently over Oklahoma, but developing further south into
Texas. Much of the convective activity is expected to congeal south
and west of the Metroplex, but urban concerns and some expected
development over the Metroplex still heighten the flash flooding
risk into the lower-end Slight category. Meanwhile, while
convection will be more numerous and strong further south and west,
less urban development may help to mitigate the flash flooding
threat a bit. By late evening, around 03Z/10pm CDT or so, the
convection is expected to have organized into a mostly single line
of storms that will progressively shift southeast towards the Gulf.
This should greatly mitigate the flash flooding threat by that
point and beyond. Thus, the flash flooding threat is greatest in
the late afternoon and evening while the storms are still
organizing and therefore have more chaotic and slow forward motions.

Wegman

...Previous Discussion...

The overall forecast philosophy for the new Day 1 period remains
largely consistent with the previous thinking, though an upgrade to
a Slight Risk has been introduced for portions of Central and
North Texas. While some uncertainty remains regarding the exact
evolution of the convective elements, a growing signal for higher-
end rainfall totals is becoming evident in the latest guidance.

Totals of 2-4 inches are increasingly likely across portions of
Central and North Texas by the late afternoon and evening,
supported by a moist, unstable airmass and strong ascent. Deepening
moisture is expected to pool along a composite surface boundary,
with PWs climbing to around 1.5 inches near the intersection of the
cold front and dryline. This moisture is expected to interact with
strong low level convergence and increasing upper level divergence
as a shortwave trough moves east, generating numerous storms
capable of producing heavy rainfall rates.

Further raising the concern for heavy amounts and potential flash
flooding will be cell training. Storms developing along the
boundary and ahead of the approaching wave may track over some
areas repeatedly, leading to localized excessive totals. Both the
HREF and RRFS indicate the potential for this setup, showing their
highest probabilities for QPF exceeding 2 inches extending from
parts of Central into North Texas, including southern sections of
the DFW Metro. Therefore, the Slight Risk was introduced to reflect
increasing confidence for scattered flash floods within this area.

Elsewhere, the Marginal Risk was expanded a bit, but remains
centered across much of the same region, reflecting the potential
for convective storms and heavy rainfall rates, though with less
organization or lower confidence in the potential for heavy
accumulations in comparison to the upgraded Slight Risk area.

Pereira


Day 2
Valid 12Z Mon May 11 2026 - 12Z Tue May 12 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL
GULF COAST...

...18Z Update...

A Marginal Risk of excessive rainfall was introduced for the
central Gulf Coast with this update. A strong cold front pushing
south out of the interior U.S. will interact with still sufficient
Gulf moisture (PWATs between 1.5 and 1.75 inches) along the coast
to force a renewed round of convection ahead of the front, which
may also interact with the sea breeze. Corfidi vectors suggest
storm movement will be fast towards the east, so backbuilding
potential appears low. However, this area was hard-hit with heavy
rain totaling over 3 inches in several areas of southeast
Louisiana, with totals up to 2 inches across much of the rest of
the Marginal Risk area just yesterday. Thus, while the area will be
recovering today through tomorrow morning, expect that any heavy
rainfall of meaningful duration may still lead to an instance of
flash flooding or 2, especially in the urban areas within the
Marginal Risk.

Wegman


Day 3
Valid 12Z Tue May 12 2026 - 12Z Wed May 13 2026

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

Wegman
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 110808
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
408 AM EDT Mon May 11 2026

Day 1
Valid 12Z Mon May 11 2026 - 12Z Tue May 12 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL
GULF COAST...

Renewed convection expected along the Gulf coast as a strong cold
front pushes south into the Gulf. Sea breeze and pooling PW values
of 1.5 to 2.0 inches will help enhance rainfall along the central
Gulf Coast. Recent rainfall has increased soil saturation for
parts of the region which in turn reduces the amounts needed for
isolated instances of flash flooding. The latest guidance has areal
averages of 1 to 3 inches with very local maximums of 4+ inches.
The environment will be conducive for progressive storm motion
which may limit the threat for flooding problems, however isolated
flash flooding with be possible especially over sensitive soils. A
Marginal Risk remains in effect from eastern Texas to the Florida
Panhandle.

Campbell


Day 2
Valid 12Z Tue May 12 2026 - 12Z Wed May 13 2026

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

Campbell


Day 3
Valid 12Z Wed May 13 2026 - 12Z Thu May 14 2026

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

Campbell
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)

FOUS30 KWBC 120811
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
411 AM EDT Tue May 12 2026

Day 1
Valid 12Z Tue May 12 2026 - 12Z Wed May 13 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR ALONG THE
I-95 CORRIDOR IN FLORIDA...

Heavy rainfall possible along the eastern coast of Florida during
this period as a cold front advances southward through the state.
Onshore flow along with pooled PW values in excess of 1.75 inches
will help fuel enhanced rainfall initially. Diurnal seabreeze=20
effects will interact further with the cold front, with a=20
convergence axis expected along the east coast of Florida.
HREF neighborhood probabilities suggest a high likelihood (over=20
90%) of QPF exceeding 3 inches, and a moderate chance (around=20
60-80%) over the urban center of Jacksonville. Due to ongoing=20
drought conditions, most of the rainfall will be beneficial which=20
will result in a low-end marginal threat for much of the eastern=20
coastline of Florida.

Campbell


Day 2
Valid 12Z Thu May 14 2026 - 12Z Fri May 15 2026

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

Campbell


Day 3
Valid 12Z Thu May 14 2026 - 12Z Fri May 15 2026

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

Campbell
$$
--- MultiMail/DOS
* Origin: Project Scorpio TEST (618:250/6)