FOUS30 KWBC 060830
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
430 AM EDT Wed May 6 2026

Day 1
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...

On-going convection at the start of the Day 1 period will linger
over portions of Arkansas. northern Mississippi and adjacent
portions of Tennessee as a cold front progresses into a most and
unstable atmosphere. Given the alignment of the storm motion and
the boundary...some training will continue with localized rainfall
totals of 1 to 2 inches before convection wanes. WPC Mesoscale
Precipitation Discussion was issued covering this area valid
through 1320Z.

The high-resolution guidance continued to struggle at eh 06/00Z
production cycle and continued with their earlier idea of bimodal
distribution to the heavy rainfall while coarser scale models
tended to have a more uniform distribution of rainfall but with
different orientations. Both the Latest HREF/RRFS guidance showed
some 15+ percent neighborhood probabilities of 24 hr QPF exceeding
10 year ARIs over portions of Mississippi and Alabama. This led to
a southward expansion of the Slight Risk area. Elsewhere...rainfall
amounts of 1 to 2 inches in an hour should be reachable within the
Slight Risk area but the signals as to where this happens are not
as strong. With increasing input from the convective allowing
models...further increases in expected rainfall amounts and better
agreement are possible which might result in an upgrade with future updates.

Bann


Day 2
Valid 12Z Thu May 07 2026 - 12Z Fri May 08 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
TEXAS EASTWARD TO GULF COAST REGION AND SOUTHEAST UNITED STATES...

Abundant moisture along a stalled frontal boundary on Thursday
will support additional thunderstorm formation along the front.
Rapidly weakening forcing at the surface and aloft will greatly
diminish convective coverage and restrict the parameters favorable
for heavy to excessive rainfall along the Gulf Coast and into
central Georgia and South Carolina. Given differences in the way
numerical guidance has in terms of how fast the front is
progressing...there was some continued adjustments to the placement
of the Marginal risk area.

South TX Brush Country...

An upper low with an associated surface boundary approaching the
region should lead to increasing chances for showers and
thunderstorms. Expectations are that most of the convection in this
time frame will remain west of the international border but there
are enough models showing some storms making east of the Rio Grande
River with isolated heavier amounts and inferred rainfall rates
that could lead to isolated flooding concerns during the late day/evening.

Bann


Day 3
Valid 12Z Fri May 08 2026 - 12Z Sat May 09 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE LOWER- AND CENTRAL TEXAS COAST ON FRIDAY...

Attention shifts to the Lower Texas coast for a risk of excessive
rainfall as shortwave energy nears the region from the southern
Great Basin and northern Mexico. Low level flow backs in response
to the approaching shortwave which results in precipitable water
values to exceed 2 inches along the immediate coastline. This
occurs at the same time flow aloft is expected to become
increasingly difluent and when the CAPE is approaching 1000 J per
kg. This should result in growing coverage of convection that will
be capable of producing rainfall rates sufficiently high to result
in isolated instances of flash flooding.

Bann

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE GULF COAST AND SOUTHEAST UNITED STATES...

The risk of excessive rainfall will be focused along the low-level
boundary that builds into the region on Day 2 and stalls along a
west to east axis. Precipitable water values in excessive of 1.5
inches should be pooling along the boundary on Friday...with higher precipitable water values returning northward later in the day on
Friday and through Friday night/early Saturday morning.

Southern stream shortwave energy become southerly during the day
and increases.

The Marginal risk area is conditional in the sense that a Slight
could be needed depending on observed rainfall on Day 2, the
degree of overlap with Day 3 QPF and the amount of urbanization.

Bann
$$
--- SBBSecho 3.28-Linux
* Origin: Capitol City Online (618:250/10)

FOUS30 KWBC 070810
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
410 AM EDT Thu May 7 2026

Day 1
Valid 12Z Thu May 07 2026 - 12Z Fri May 08 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM SOUTHERN
ALABAMA AND THE FLORIDA PANHANDLE TO SOUTHERN GEORGIA...

...Gulf Coast/Southeast...
While the overall coverage and intensity will likely be
diminishing, showers and storms will remain ongoing with the
potential for additional heavy amounts and flash flooding concerns
beyond 12Z this morning. A Marginal Risk was maintained across
portions of southern Alabama, the Florida Panhandle, and southern
Georgia. A 40-50 kt southwesterly low level jet ahead of an
approaching front will continue to support PWs around 2 inches,
which along with favorable upper jet forcing will likely support
the continuation of some storms with heavy rainfall rates well into
the morning. Both the HREF and RRFS indicate that localized
additional amounts of 1-2+ inches are likely. This is expected to
occur mostly, if not entirely, within the first 6 hours of the
period before the deepest moisture and the better forcing moves downstream.

...Rio Grande Valley...
The Marginal Risk has been removed. While a weak surface low and
approaching shortwave trough will support convective development
over the mountains of Mexico, the majority of the models indicate
that the bulk of the heavy rainfall will remain south of the
international border. While an isolated heavy total remains
possible, and the threat for flash flooding across South Texas is
non-zero, the coverage is no longer expected to meet Marginal Risk criteria.

Pereira


Day 2
Valid 12Z Fri May 08 2026 - 12Z Sat May 09 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM SOUTH TEXAS
GULF COAST THROUGH THE LOWER MISSISSIPPI VALLEY...

The synoptic pattern on Friday will characterized by the return of
deep moisture as a previously stalled front, lingering along the
Gulf Coast begins to lift northward as a warm front. PWs are
forecast to climb above 1.75 inches from South Texas through the
lower Mississippi Valley, providing an ample reservoir for heavy
rainfall. This moisture, along with an upper level low moving into
West Texas and downstream shortwave energy/upper jet forcing, are
expected to support numerous showers and storms with the potential
for heavy rates. However, while the environment is expected to be
favorable for numerous showers and storms to develop, confidence in
the placement of the heaviest rainfall has diminished with this
cycle, with significant model spread regarding where the most
intense convective clusters will organize. Therefore, the Slight
Risk that was previously carried from southeastern Texas through
the lower Mississippi Valley has been removed for now. The
reintroduction of a Slight Risk may be warranted in future updates, particularly farther southwest across South Texas closer to the
ejecting upper low/shortwave, but predictability is too low to
maintain the higher category. For now, will maintain a broad
Marginal Risk extending from South Texas to southern Mississippi.

Pereira


Day 3
Valid 12Z Sat May 09 2026 - 12Z Sun May 10 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF
THE LOWER MISSISSIPPI VALLEY AND THE CENTRAL GULF COAST...

The previously noted upper level low moving across southern Texas
on Day 2 will continue to eject east, moving along the central Gulf
Coast into the Southeast -- deamplifying as it becomes embedded
within the base of a broad upper trough centered over the central-
eastern U.S. Deep moisture remaining ahead of this wave and along a
slow-moving boundary will continue to fuel shower and storm
development capable of producing heavy rainfall. Similar to Day 2,
confidence was lacking for any upgrades beyond a Marginal Risk.
However, should the models start to move into better agreement, an
upgrade may be warranted in future updates -- especially if the
guidance begins to show a growing signal for heavy amounts across
areas impacted by recent heavy rains.

Pereira
$$
--- SBBSecho 3.28-Linux
* Origin: Capitol City Online (618:250/10)

FOUS30 KWBC 080800
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Fri May 8 2026

Day 1
Valid 12Z Fri May 08 2026 - 12Z Sat May 09 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
SOUTHEASTERN LOUISIANA AND SOUTHERN MISSISSIPPI...

...Lower Mississippi Valley/Central Gulf Coast...
A robust moisture pool is expected to deepen along the central Gulf
Coast today as southwesterly winds amplify ahead of energy moving
out of eastern Texas and the northwestern Gulf. This flow will
support PWs climbing to around 2 inches along a slow-moving front,
or more than 2.5 std dev above normal. The majority of the CAMs
are in good agreement indicating a corridor of training convection
developing by the afternoon across southeastern Louisiana and
southern Mississippi. Given the high moisture content and potential
for training, localized totals of 2-3+ inches are possible. High
hourly rates within these training storms will pose a risk for
flash flooding, particularly in low-lying and urban areas, with
the highest potential impact centered along the I-10 corridor. The
introduced Slight Risk area reflects high neighborhood
probabilities shown by both the HREF and RRFS for amounts exceeding 2 inches.

...South Texas...
Farther west, a well-defined mid-to-upper level shortwave/low
moving through northern Mexico into West Texas will provide
increasing ascent. Moist southerly flow interacting with this
feature and upslope into the Sierra Madre Oriental will support
storms developing over northeastern Mexico. While much of this
activity may remain south of the international border, there are
some hi-res members that show some of these convective clusters
moving into South Texas. Though model spread is higher in this
region, both the HREF and RRFS indicate that localized totals
exceeding 2 inches are possible. Therefore, a Marginal Risk was
maintained to account for this potential.

Pereira


Day 2
Valid 12Z Sat May 09 2026 - 12Z Sun May 10 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE CENTRAL
GULF COAST INTO THE SOUTHEAST...

The previously noted shortwave moving into West Texas on Day 1 is
forecast to move eastward along the central Gulf Coast on Saturday.
While lingering deep moisture will remain in place, the synoptic
signal for organized and widespread heavy rainfall becomes
significantly more diffuse. Current model guidance lacks a
concentrated signal for high-end totals, suggesting a more isolated
or low-end flash flood threat. Given the environment and the
potential for antecedent conditions driven the previous day's heavy
rains, the current Marginal Risk was maintained for this cycle. But
should model trends continue to show a lack of organization, this
area may be discontinued in future updates.

Pereira


Day 3
Valid 12Z Sun May 10 2026 - 12Z Mon May 11 2026

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS
OF NORTHEASTERN TEXAS, SOUTHEASTERN OKLAHOMA, SOUTHERN ARKANSAS,
AND NORTHERN LOUISIANA...

Shortwave energy diving into the base of broader scale trough will
drive a cold front southward across the region. Southerly flow
ahead of the boundary will boost PWs to over 1.5 inches. This
moisture, combined with favorable upper jet forcing, will support
storms developing along and ahead of the front. While model spread
is currently too high to support a higher risk area and the signal
for widespread heavy totals remains muted, locally intense rates
along with some areas of repeating cells could result in isolated
flash flooding.

Pereira
$$
--- SBBSecho 3.28-Linux
* Origin: Capitol City Online (618:250/10)