FOUS30 KWBC 030033
QPFERD
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
833 PM EDT Fri Oct 2 2026
Day 1
Valid 01Z Sat Oct 03 2026 - 12Z Sat Oct 03 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL TEXAS...
01Z Update...
Few changes needed with this outlook. The potential for excessive
rainfall remains greatest within a plume of deeper moisture
extending from southwest to northeast. Concern is not so much
about additional blockbuster amounts but where additional rainfall
overlaps with hydrologically sensitive areas. Probabilities from
the HREF and the RRFS both indicate some potential across the
central portion of the state for one hour rainfall amounts in
excess of 0.50 inches where the corresponding flash flood guidance
was low. Maintained the Slight Risk area there. Also maintained the
Marginal Risk area extending into the Mid-South where the
HREF/RRFS and several cams suggest an uptick in rates later
tonight. It should be noted that rainfall rates have not
materialized in this area that were advertised by the same
guidance.
Bann
16z Update: The latest changes to the Excessive Rainfall Outlook
included trimming the Slight Risk out of southern Oklahoma to
account for lower rainfall rates currently over the region and the
latest model guidance indicating small probabilities for exceeding
flash flood guidance and 24 hr QPF 2 inch probabilities. The
higher end Slight Risk ERO outlook across central and southern
Texas looks to remain on track. A moist environment with low level
convergence nearby a front in the region has allowed for slowly
propagating, efficient rain producing showers and thunderstorms to
persist near Dallas to the Rio Grande region. In particular, the
I-35 corridor near Dallas-Fort Worth to San Antonio will remain a
focal point for flash flooding as a couple of additional inches of
rain has fallen this morning over areas with flash flood guidance
less than half an inch per hour. An additional rainfall of 1-3
inches is possible today over this region.
Other changes to the forecast included trimming eastern and
northern portions of the Tennessee and Ohio Valley Marginal Risk
where rainfall generally remains stratiform primarily from lower
instability across the region. Across the Gulf Coast, the Marginal
Risk was expanded eastward across the I-10 corridor to encompass
the Jacksonville metro on account of model guidance showing 2-3+
inches of rainfall in thunderstorms that form in a tropical air
mass with the addition of diurnal heating.
Wilder
...Previous Discussion...
..Texas..
An expansive front is in place from Mexico through Texas and into
the Midwest to the Northeast this morning. The southern end of the
front draped across Texas and Oklahoma will become a slow-moving
warm front, gradually drifting northwestward through the day.
Southeast of the front, southeasterly flow of very moist, tropical
air will run into the front. Northwest of the front, northeasterly
flow down the front will keep conditions much drier and more
stable. This clash of air masses will keep the front, and act as a
potent forcing mechanism for showers and thunderstorms. 2-4 inches
of rain fell along the I-35 corridor yesterday. The return of the
front will drop an additional 1-3 inches along much of the I-35
corridor today. Between the urban centers from San Antonio, Austin,
and up to the Metroplex, and very saturated soils in those cities
and everywhere in between, the additional rain is likely to cause
additional instances of flash flooding. Instability will
fortunately be limited, which should prevent any storms from
producing high instantaneous rates of rainfall. However, the slow-
moving front will still allow the storms to train along it.
A small higher-end Slight was issued from Austin through the
Metroplex, to account for urban concerns mostly. The inherited
Slight risk was expanded northeastward to include the southeast
corner of Oklahoma, which picked up 1-3 inches of rain yesterday.
Topography in that area against the Ozarks could lead to locally
higher totals in this flood-prone area.
Along the Gulf Coast, the inherited Marginal was shifted west, away
from the Big Bend of Florida, which is difficult to flood, and
including the New Orleans and Baton Rouge metros, which are flood-
prone. Guidance suggests most of the heaviest rainfall will remain
offshore, but enough activity may affect the immediate coast to
begin moistening up the soils today.
Wegman
Day 2
Valid 12Z Sat Oct 03 2026 - 12Z Sun Oct 04 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL
GULF COAST AND SOUTHERN COASTAL TEXAS...
..20z Update..
Southern Coastal Texas: A Slight Risk ERO was introduced across
southern coastal Texas from areas north of Corpus Christi
southwards to Brownsville. Synoptically, a slow moving frontal
boundary will be present across the region and focus surface
convergence to enhance thunderstorm coverage. Moreover, a mid-level
wave traversing the Gulf will increase moisture transport and
frictional convergence along the southern Texas coastline that may produce locally heavy precipitation. Some of the precipitation could
overlap with areas that have received heavy rainfall over the past
few days and have saturated soils, which was also taken into
consideration for the introduction of a Slight Risk. Overall, QPF
amounts of 2-4 inches are reasonable, particularly close to the
coast line and locally higher amounts may be realized as indicated
by the latest HREF 24 hr QPF 50-70% probabilities of exceeding 5
inches.
Central Gulf Coast: No major changes were made to the forecast
expectation of tropical moisture to surge into the central Gulf
Coast and result in locally heavy rainfall and scattered instances
of flash flooding. A mid-level wave moving northward across the
Gulf will increase moisture transport from coastal Louisiana to
the Florida Panhandle and advect anomalously high PWATS over 2.5
inches that will fuel tropical rains. The latest QPF forecast has
3-5 inches with localized maximum of 5-7 inches for the 24 hour
period on Saturday with a tight gradient of the highest QPF along
and south of I-10. Flash flooding impacts will be greater near the
coastline and mainly realized over locations that see the higher
end rainfall totals. In terms of changes, the Slight Risk was
trimmed closer to the central Gulf Coast coastline and the Slight
Risk was removed from the eastern Texas coastline as models showed
the highest QPF remaining offshore.
Carolinas: An approaching cold front and a surge of PWATS above 2
inches will focus a swath of heavier precipitation across South
Carolina into eastern North Carolina. The forecast calls for an
average of 2-3 inches of rain with a maxima of 3-5 inches possible
as indicated by CAMS. The greatest confidence for the higher QPF
amounts are over southeastern North Carolina where there are 50-70% probabilities for 24 hr QPF exceeding 5 inches. However, these
same areas are exceptionally dry and have 3 hour flash flood
guidance exceedance values nearing 5 inches. Instability is also
forecast to be around 1000 J/Kg or less in the Carolinas, which
will also limit the coverage of 2+ inch hourly rainfall rates. All
said, this a higher end Marginal Risk with some scattered instances
of flash flooding possible, but the underlying hydrology of the
area precluded a Slight Risk at the time.
Wilder
...Previous Discussion...
Broad southerly flow off the Gulf will pump increasing amounts of
deep tropical moisture northward into the central Gulf Coast on
Saturday. PWATs will continue to climb from previous days, likely
exceeding 2.5 inches across portions of the central Gulf coast.
Extensive cloud cover due to the extreme amounts of atmospheric
moisture and the early October sun should generally limit
instability except along the immediate coast, where the greatest
threat lies. Due to numerous urban areas along the coast, the
Slight was largely maintained. While it's uncertain which areas
will see the most rainfall, everywhere from Houston through
Pensacola have some threat for prolonged heavy rainfall on
Saturday. The Slight was expanded west to include the Houston
metro, in coordination with HGX/Houston, TX forecast office. Even
there the greatest threats will be along the coast, with the lower
threats north and west of Houston. A similar scenario is in place
for New Orleans, Biloxi, Mobile, and Pensacola. For those latter
cities, their locations along the coast will make them more prone
to potential heavy rainfall Saturday afternoon. The Slight risk
balances the second consecutive day of heavy rain and urban threats
with very high amounts of available moisture against prior dry
soils and very high FFGs due to sandy and flat, swampy areas that
are highly flood-resistant.
Across the Carolinas, a slow southward-moving cold front will run
into the same highly moist air mass. There will likely be an area
of enhanced rainfall, generally stretching from 50 miles or so on
either side of the NC/SC border. Very dry soils going in should
generally preclude all but isolated flash flooding outside of any
urban areas, such as Charlotte and Greenville/Spartanburg. A lack
of instability will also prevent much heavy rain from occurring, in
favor of a long-duration light to moderate rainfall event.
Wegman
Day 3
Valid 12Z Sun Oct 04 2026 - 12Z Mon Oct 05 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE SOUTHEAST AND ALONG THE SOUTHERN TEXAS COASTLINE ...
..20z Update..
Coastal Southern Texas: A Slight Risk of Excessive Rainfall was
introduced for day 3, Sunday, across south coastal Texas. The
Slight Risk is confined within Brownsville's CWA. Similarly to the
day 2 period, a mid-level trough will be slowly traversing the
northern Gulf, which will provide enhanced northeasterly flow and
accompanied moisture transport off the Gulf into coastal zones.
There is also a lingering stationary/coastal front progged near
coastal Texas that will only further concentrate locally heavy
showers and thunderstorms with an over-running pattern (isentropic
lift). QPF totals of 3-4 inches close to the coastline are in
rather good agreement in regards to the official WPC,NBM, and
ensemble QPF. This rainfall will be on top of potentially heavy
rainfall from the day 2 period, leading to increased chances of
localized flash flooding.
Southeast: The Slight Risk ERO across the Southeast remains on
track as of this afternoon. An area of disturbed weather in the
Gulf will begin to trek inland across the Southeast and bring
locally heavy rainfall to northern Florida, portions of southern
and central Alabama and Georgia, and northeast into the Carolinas.
A cold front dropping down into the Southeast will also interact
with northward streaming tropical moisture to enhance higher
rainfall totals around 2-3 inches. This QPF will overlap with
Saturday's rainfall to produce 2 day totals of 3-5 inches from
central Alabama to the Carolinas. Saturated soils will increase
the chances for scattered instances of flash flooding on Sunday
across the Southeast. The same logic applies along the northern
Gulf Coast from Louisiana to the Florida Panhandle where
compounding rainfall totals of 4-8 inches, locally as high as 10,
from Saturday and Sunday may enhance flooding potential. The
greatest impacts from flash flooding remain likely closer to the
Gulf Coast and northwards to central Alabama, Georgia, and the
coastal Carolinas. Model guidance also showed a southward shift of
the heaviest QPF and instability overlap. Therfore,the Slight Risk
was trimmed out of the northern portions of these states and
across the upper Tennessee Valley.
Wilder
...Previous Discussion...
A progressive cold front pushing southeast from the Ohio Valley
will run into an extremely moisture-rich air mass that will start
the day entrenched across much of the Southeast. The result between
the strong forcing of the front and a highly moist air mass will be
large areas of heavy rain across much of the Southeast on Sunday.
As on previous days, instability will still work to temper rainfall
rates in any individual storms, but due to the ample moisture in
place, a longer duration rain is expected as the storms ride
northeastward along the front. Numerous urban areas from Atlanta,
Charlotte, Birmingham, and New Orleans may all be impacted by heavy
rain on Sunday. With Saturday likely having moistened up most of
the soils across the Southeast, the heavier rain totals expected on
Sunday are likely to cause widely scattered instances of flash
flooding over much of the Southeast, especially in the southern
Appalachians, urban areas, and other flood-prone low-lying areas.
For these reasons, the Slight Risk was expanded greatly across much
of the Southeast, to include all of Alabama, Georgia, and South
Carolina. While localized areas with higher risks are possible,
those will be largely dependent on the rainfall footprints of prior
days, so due to uncertainty, the highest threat level will remain
at a Slight for this update.
On the northern end, to include the DMV, a lack of instability may
preclude the rates or duration of rainfall needed to cause isolated
flash flooding. With some uncertainty as to where the front will be
on Sunday, the area is in a low-confidence Marginal, which will
likely be trimmed southward with time.
Wegman
Day 4 and Day 5
Valid 12Z Mon Oct 05 2026 - 12Z Wed Oct 07 2026
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER THE LOWER
TEXAS COAST AND PARTS OF THE SOUTHEAST..
2030Z Update...The pattern is much more quiet than the days leading
into the period with a cold front over part of the Southeast US and
Gulf coast region providing the focus for any excessive rainfall
potential. Did expand the northern boundary of the Marginal on Day
4 in the Southeast a bit in deference to the the placement of the
highest QPF contours of both the EC ECens and GEFS. No changes of
note were made to Day 5.
Bann
Previous Excessive Rainfall Discussion...
For Day 4 (12Z Mon-12Z Tue) -- Continued the Marginal Risk over the
Lower TX Coast inherited from yesterday's Day 5 ERO. This is where
the surface front would more likely get hung up, as both the 00Z
ECMWF and GFS show stretched mid-level vort lobes lingering across
South TX along a strong NW-SE PW gradient (with PWs remaining
between 2-2.25" until very late in the period (late Mon night). At
this time, the guidance shows a very compact area of heavier rain
(higher deterministic and probabilistic QPF) onshore from the Gulf,
basically along the Lower TX Coast and into eastern portions of
the Rio Grande Valley.
Farther east (Eastern Gulf Coast/Southern GA-North FL), was able to
cut back on the Marginal Risk area north and west of Tallahassee,
based on the latest guidance trends, including the 3-5" 24hr
rainfall probabilities per the GEFS/ECENS/CMC. Given the projected
mid/upper level height falls into the Southeast on Day 4 per the
latest models (588dm H5 heights through Central FL), feel the
surface front and ensuing more stable, drier airmass (strong
negative PW advection) behind it will be more progressive than
previous forecast expectations.
On Day 5 (12Z Tue-12Z Wed) -- Marginal Risk area slips a little
farther south into North-Central FL and far southeast GA, where the
surface front more than likely will begin to stall and become
quasi-stationary. The axis of highest PWs (2-2.5") and mid-level
shortwave energy will be draped along and south of the front, as
will some (albeit weak) deep-layer instability. Deep west/west-
southwesterly flow will enhanced the risk for training cells coming
off the eastern Gulf, as all the global ensembles (GEFS/ECENS/CMC)
have at least some members noting rainfall exceeding 3-5" within
the 24hr period.
Hurley
Day 1 threat area:
https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt__;!!DZ3fjg!-opfc2cx1cr36luzxB4inozdKTJ7XouDvLIhLwG8Y9YodFDoC73dAsgC_lTuTT-jN0rclrsVwyHrH0euxD9glTQRMsA$
Day 2 threat area:
https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt__;!!DZ3fjg!-opfc2cx1cr36luzxB4inozdKTJ7XouDvLIhLwG8Y9YodFDoC73dAsgC_lTuTT-jN0rclrsVwyHrH0euxD9gLm-IRb4$
Day 3 threat area:
https://urldefense.com/v3/__https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt__;!!DZ3fjg!-opfc2cx1cr36luzxB4inozdKTJ7XouDvLIhLwG8Y9YodFDoC73dAsgC_lTuTT-jN0rclrsVwyHrH0euxD9gyvzrDNE$
$$
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