186
FXUS21 KWNC 261826
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 26 2025
SYNOPSIS: THE MAJOR STORY LEADING UP TO THE WEEK-2 PERIOD IS THE DEVELOPMENT OF
A TROPICAL DISTURBANCE OVER THE WESTERN ATLANTIC (AL94), AND ITS POTENTIAL TO
BRING SIGNIFICANT RAINFALL AND FLOODING TO PORTIONS OF THE MID-ATLANTIC,
SOUTHEAST, AND SOUTHERN APPALACHIANS DURING WEEK-1. HOWEVER, THE FORECAST IS
COMPLEX GIVEN THAT SOME LEVEL OF INTERACTION WITH THE CIRCULATION OF HURRICANE
HUMBERTO MAY RESULT IN THE SYSTEM BEING PULLED OUT TO SEA OR MEANDERING CLOSER
TO THE COAST, WHICH COULD HELP MITIGATE IMPACTS FURTHER INLAND. FOR THE
REMAINDER OF THE CONTIGUOUS U.S. (CONUS), WEEK-2 IS RATHER UNEVENTFUL, WITH
BROAD MID-LEVEL HIGH PRESSURE FAVORING ABOVE-NORMAL, BUT NOT HAZARDOUS
TEMPERATURES.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE COASTAL MID-ATLANTIC
AND SOUTHEAST, SAT-MON, OCT 4-6.
SLIGHT RISK OF HIGH WINDS ACROSS PORTIONS OF THE COASTAL MID-ATLANTIC AND
SOUTHEAST, SAT-MON, OCT 4-6.
FLOODING POSSIBLE ACROSS PORTIONS OF THE MID-ATLANTIC, SOUTHEAST, AND SOUTHERN
APPALACHIANS.
RAPID ONSET DROUGHT (ROD) POSSIBLE FOR PARTS OF TEXAS AND LOUISIANA.
DETAILED SUMMARY
FOR MONDAY SEPTEMBER 29 - FRIDAY OCTOBER 03:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY OCTOBER 04 - FRIDAY OCTOBER 10: THE WEATHER ACROSS THE SOUTHEAST
AND EAST COAST OF THE U.S. EARLY IN WEEK-2 IS LARGELY DEPENDENT ON THE
EVOLUTION OF TROPICAL DISTURBANCE AL94, CURRENTLY NEAR HISPANIOLA. THE NATIONAL
HURRICANE CENTER (NHC) DESIGNATES THIS SYSTEM AS HAVING AN 90 PERCENT CHANCE OF
DEVELOPING INTO A TROPICAL CYCLONE DURING THE NEXT 48-HOURS, WHILE TRACKING TO
THE NORTH OR NORTH-NORTHWEST. THE FORECAST BECOMES EXTREMELY COMPLICATED GIVEN
THE ENLARGING CIRCULATION OF HURRICANE HUMBERTO OVER THE WESTERN ATLANTIC. AS
THE TWO SYSTEMS MOVE CLOSER IN PROXIMITY TO EACH OTHER, SOME LEVEL OF
INTERACTION IS POSSIBLE (FUJIWHARA EFFECT), WHICH MAY INTRODUCE A SOUTHERLY OR
EASTERLY COMPONENT INTO THE MOTION OF 94L AND PREVENT IT FROM REACHING THE
COAST. HOWEVER, A GROWING NUMBER OF ENSEMBLE SOLUTIONS INCLUDING THOSE FROM THE
0Z ECENS AND GEFS ARE SUPPORTIVE OF A FASTER 94L TAKING A MORE INLAND TRACK.
THIS WOULD RESULT IN A MAJOR HEAVY RAIN AND FLOODING EVENT OVER PORTIONS OF THE
MID-ATLANTIC, SOUTHEAST, AND SOUTHERN APPALACHIANS AS THE SYSTEM WOULD MEANDER
ACROSS THE SOUTHEAST DUE TO A STRONG AREA OF SURFACE HIGH PRESSURE TO THE
NORTH. THE WEATHER PREDICTION CENTER (WPC) IS CURRENTLY PREDICTING WEEK-1
RAINFALL TOTALS IN EXCESS OF 4-INCHES OVER PORTIONS OF THE CAROLINAS AND INTO
SOUTHERN VIRGINIA WHICH COULD TRIGGER RIVER AND FLASH FLOODING, WITH HIGHER
ELEVATION INLAND AREAS ALSO BEING AT RISK. IF THIS SCENARIO UNFOLDS, THE
FLOODING WOULD LIKELY LINGER INTO WEEK-2, JUSTIFYING INCLUSION OF FLOODING
POSSIBLE IN THE WEEK-2 HAZARDS OUTLOOK.
BY THE OUTSET OF WEEK-2, THE SURFACE HIGH PRESSURE OVER THE NORTHEAST IS
FORECAST TO WEAKEN. THIS MAY RESULT IN THE REMNANT LOW OF AL94 TRACKING
NORTHWARD, BRINGING ENHANCED RAINFALL INTO PARTS OF THE NORTHERN MID-ATLANTIC
AND NORTHEAST AS IT INTERACTS WITH A STATIONARY FRONTAL BOUNDARY ALONG THE
COAST. THE ECENS PROBABILISTIC EXTREMES TOOL (PET) DEPICTS PROBABILITIES OF AT
LEAST 20 PERCENT FOR 3-DAY PRECIPITATION EXCEEDING THE 85TH CLIMATOLOGICAL
PERCENTILE AND 1-INCH EXTENDING UP THE EAST COAST INTO SOUTHERN NEW ENGLAND
DURING WEEK-2, WITH BOTH THE DETERMINISTIC 0Z GFS AND 0Z ECMWF DEPICTING A
NORTHWARD TRACKING SYSTEM EARLY IN WEEK-2. HOWEVER, THE GEFS PET SHOWS VERY
LITTLE SIGNAL FOR HEAVY PRECIPITATION BEYOND WEEK-1, WITH MANY INDIVIDUAL 0Z
GEFS ENSEMBLE MEMBERS DISSIPATING THE SYSTEM PRIOR TO THE START OF THE PERIOD.
GIVEN THE UNCERTAINTIES DURING WEEK-1, THERE IS EVEN LESS CONFIDENCE DURING
WEEK-2. IN ADDITION TO THE FLOODING POSSIBLE AREA, A SLIGHT RISK OF HEAVY
PRECIPITATION IS POSTED ALONG THE EASTERN SEABOARD FROM NORTHEAST FLORIDA
THROUGH SOUTHERN NEW JERSEY, OCT 4-6, TO ACCOUNT FOR AT LEAST SOME POSSIBILITY
AL94 OR ITS REMNANTS PERSIST INTO THE PERIOD. THE STRONG GRADIENT BETWEEN THE
SURFACE HIGH TO THE NORTH AND RELATIVELY LOWER PRESSURES OVER THE SOUTHEAST
ALSO SUPPORTS A SLIGHT RISK OF HIGH WINDS ALONG THE SOUTHEAST AND MID-ATLANTIC
COASTS, OCT 4-6. THE ECENS PET DEPICTS A 20-40 PERCENT CHANCE WIND SPEEDS
EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE AND 25-MPH.
INTERESTS ACROSS THE MID-ATLANTIC AND SOUTHEAST, AND FURTHER INLAND ACROSS THE
SOUTHERN APPALACHIANS, SHOULD MONITOR UPDATES FROM NHC, WPC, AND THEIR LOCAL
WEATHER FORECAST OFFICES (WFOS) REGARDING THE CONTINUED EVOLUTION AND IMPACTS
FROM AL94 DURING THE NEXT WEEK.
THE 0Z ECENS AND GEFS INDICATE BROADLY POSITIVE 500-HPA HEIGHT ANOMALIES OVER
MUCH OF THE CONUS DURING WEEK-2 TIED TO INITIAL RIDGING OVER EASTERN CANADA,
FOLLOWED BY ADDITIONAL RIDGING DEVELOPING ACROSS THE CENTRAL CONUS TOWARD THE
MIDDLE OF THE PERIOD. THIS PATTERN SUPPORTS ABOVE-NORMAL TEMPERATURES OVER MUCH
OF THE CONUS, WITH THE LARGEST POSITIVE TEMPERATURE ANOMALIES (UP TO +10 DEG F)
FAVORED ACROSS THE UPPER MIDWEST. WHILE THIS WOULD BE CONSIDERED UNSEASONABLY
WARM BY FALL STANDARDS, IT IS NOT HAZARDOUS WITH TEMPERATURES GENERALLY IN THE
60S AND 70S DEG F. ALTHOUGH TEMPERATURES ARE LIKELY TO BE WARMER FARTHER SOUTH
ACROSS THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY (80S TO LOW 90S DEG F),
HEAT RISK GUIDANCE IS UNSUPPORTIVE OF HEAT INDICES EXCEEDING HAZARD CRITERIA,
PRECLUDING ANY TEMPERATURE RELATED HAZARDS.
SURFACE LOW PRESSURE IS PROJECTED TO TRACK THROUGH THE BERING SEA INTO THE GULF
OF ALASKA DURING WEEK-2 LEADING TO ENHANCED ONSHORE FLOW AND POTENTIALLY HEAVY
PRECIPITATION ACROSS SOUTHEAST ALASKA. HOWEVER, 24-HOUR TOTALS IN THE
UNCALIBRATED 0Z GEFS AND ECENS ARE GENERALLY UNDER 1-INCH, AND THERE IS NO
SIGNAL FOR HAZARDOUS PRECIPITATION IN THE PETS. THEREFORE, NO RELATED
PRECIPITATION HAZARD IS POSTED ACROSS SOUTHEAST ALASKA IN TODAY’S OUTLOOK,
ALTHOUGH MUDSLIDES WILL CONTINUE TO REMAIN A CONCERN OVER SOME AREAS. THE
ENHANCED PRECIPITATION MAY EXTEND INTO THE PACIFIC NORTHWEST BY THE MIDDLE OF
THE PERIOD, WITH A CORRESPONDING SLIGHT UPTICK IN THE SIGNAL IN THE PETS.
HOWEVER, AMOUNTS ARE PREDICTED TO REMAIN BELOW HAZARDS THRESHOLDS.
ACROSS PORTIONS OF TEXAS AND SOUTHWESTERN LOUISIANA, PRECIPITATION DEFICITS OF
SEVERAL INCHES HAVE ACCUMULATED DURING THE PAST 30-DAYS. PERCENT-OF-NORMAL
PRECIPITATION (PNP) FALLS WITHIN THE TWO LOWEST QUARTILES (1ST THROUGH 25TH
PERCENTILES AND 26TH THROUGH 50TH PERCENTILES) OF THE CLIMATOLOGICAL
DISTRIBUTION. ABOVE-NORMAL TEMPERATURES PREDICTED FOR THE NEXT TWO WEEKS, AND
GENERALLY LITTLE OR NO PRECIPITATION INCREASES THE POTENTIAL FOR RAPID ONSET
DROUGHT (ROD) ACROSS THIS REGION.
FORECASTER: THOMAS COLLOW
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