115
FOUS30 KWBC 021556
QPFERD
EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1156 AM EDT FRI OCT 2 2026
DAY 1
VALID 16Z FRI OCT 02 2026 - 12Z SAT OCT 03 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL TEXAS...
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...
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 MUCH OF THE
SOUTHEAST...
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...
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://WWW.WPC.NCEP.NOAA.GOV/QPF/94EPOINTS.TXT
DAY 2 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/98EPOINTS.TXT
DAY 3 THREAT AREA: HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/99EPOINTS.TXT
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