221
FXUS21 KWNC 241813
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 24 2025
SYNOPSIS: WHILE STRONG MID-LEVEL HIGH PRESSURE IS LIKELY TO KEEP MUCH OF THE
CONTIGUOUS U.S. (CONUS) UNSEASONABLY WARM FOR EARLY FALL, MID-LEVEL LOW
PRESSURE UPSTREAM OVER THE NORTHEASTERN PACIFIC IS EXPECTED TO BRING MORE
UNSETTLED WEATHER ACROSS WESTERN NORTH AMERICA WITH HEAVY PRECIPITATION
POSSIBLE OVER SOUTHEAST ALASKA DURING THE WEEK-2 PERIOD. THE TROPICAL ATLANTIC
REMAINS ACTIVE, WITH THE NATIONAL HURRICANE CENTER MONITORING THE POTENTIAL FOR
TWO TROPICAL SYSTEMS TO DEVELOP OVER THE WESTERN ATLANTIC WITHIN THE NEXT 7
DAYS. ALTHOUGH IT REMAINS UNCLEAR AS TO THE EXACT TRACK AND INTENSITY OF EACH
OF THESE TROPICAL SYSTEMS, HEAVY PRECIPITATION AND HIGH WINDS IN CONJUNCTION
WITH A NEARBY FRONTAL BOUNDARY CANNOT BE RULED OUT FOR PORTIONS OF THE EAST
COAST EARLY IN THE PERIOD.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION ALONG PORTIONS OF THE EAST COAST, THU-FRI,
OCT 2-3.
SLIGHT RISK OF HIGH WINDS FOR PARTS OF THE SOUTHEAST, APPALACHIANS,
MID-ATLANTIC, AND THE NORTHEAST, THU-FRI, OCT 2-3.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE ALASKA PANHANDLE, FRI-TUE, OCT 3-7.
DETAILED SUMMARY
FOR SATURDAY SEPTEMBER 27 - WEDNESDAY OCTOBER 01:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY OCTOBER 02 - WEDNESDAY OCTOBER 08: BOTH THE 0Z GEFS AND ECMWF
500-HPA MEAN HEIGHT FORECASTS ARE IN GOOD AGREEMENT FAVORING AN AMPLIFIED RIDGE
CENTERED TO THE SOUTH OF HUDSON BAY IN CANADA, WITH A PAIR OF MEAN LONGWAVE
TROUGHS OVER THE NORTHEASTERN PACIFIC AND THE NORTHWESTERN ATLANTIC TOWARDS THE
MIDDLE OF NEXT WEEK. WHILE THESE MID-LEVEL FEATURES CONTINUE TO RESEMBLE AN
OMEGA BLOCK PATTERN WITH STAYING POWER, DYNAMICAL MODELS DEPICT AN EASTWARD
SHIFT OF THESE FEATURES EARLY IN THE PERIOD, IMPLYING SOME PROGRESSION OF THE
PATTERN COMPARED TO PREVIOUS MODEL RUNS. PERHAPS MORE CRITICALLY, BOTH THE MEAN
CANADIAN RIDGE AND UPSTREAM TROUGHING APPEARS MORE AMPLIFIED IN THE LATEST
GUIDANCE, WHICH INCREASES OUTLOOK CONFIDENCE FOR UNSEASONABLY WARM TEMPERATURES
THROUGHOUT MUCH OF THE CONUS AS WELL AS ENHANCED ONSHORE FLOW TO PROMOTE HIGHER
PRECIPITATION AMOUNTS ACROSS MUCH OF THE WESTERN CONUS AND SOUTHEASTERN ALASKA.
DOWNSTREAM OF THE RIDGE, THERE IS ALSO BETTER MODEL SUPPORT FOR POTENTIALLY
HEAVY PRECIPITATION AND EPISODES OF HIGH WINDS ASSOCIATED WITH THE INTERACTION
BETWEEN A MID-LATITUDE FRONTAL SYSTEM AND TROPICAL ACTIVITY IN THE WESTERN
ATLANTIC LATE IN WEEK-1 AND HEADING INTO WEEK-2.
WITH NEAR TO ABOVE-NORMAL TEMPERATURES FAVORED IN THE RAW TOOLS FOR NEARLY THE
ENTIRE CONUS, PROBABILISTIC EXTREMES TOOLS (PETS) FROM THE ECMWF AND GEFS
LIKEWISE REFLECT THIS POTENTIAL INDICATING INCREASED CHANCES FOR DAYTIME
TEMPERATURES EXCEEDING THE 85TH PERCENTILE OVER MANY PARTS OF THE U.S. THESE
TOOLS SHOW THE WARMEST TEMPERATURE SIGNALS LOCATED ACROSS THE UPPER MIDWEST IN
PROXIMITY OF THE ANOMALOUS RIDGE CENTER, HOWEVER ACTUAL TEMPERATURES ARE LIKELY
TO BE BELOW 90 DEGREES F OVER THIS PART OF THE COUNTRY. AND ALTHOUGH
TEMPERATURES ARE LIKELY TO BE WARMER FURTHER SOUTH ACROSS THE SOUTHERN TIER,
GUIDANCE REMAINS UNSUPPORTIVE OF ACTUAL TEMPERATURES EXCEEDING HAZARD CRITERIA,
PRECLUDING ANY TEMPERATURE RELATED HAZARDS.
TIED TO THE ENHANCED ONSHORE FLOW OVER WESTERN NORTH AMERICA, THE PETS SHOW
INCREASED CHANCES FOR 3-DAY AMOUNTS EXCEEDING THE 85TH PERCENTILE AND 1 INCH
FROM SOUTHEASTERN ALASKA TO THE PACIFIC NORTHWEST. DESPITE AN UPTICK IN THE
RAW PRECIPITATION AMOUNTS EARLY IN WEEK-2 OVER THE PACIFIC NORTHWEST SINCE
YESTERDAY, ACTUAL AMOUNTS STILL LOOK TO REMAIN BELOW HAZARD THRESHOLDS, WITH
WPC WEEK-1 QPF AND INTEGRATED VAPOR TRANSPORT (IVT) TOOLS FEATURING THE
HEAVIEST TOTALS BECOMING MORE LIKELY TO OCCUR DURING THE WEEK-1 PERIOD.
THEREFORE, NO PRECIPITATION HAZARDS ARE POSTED FOR THIS PART OF THE COUNTRY,
HOWEVER A SLIGHT RISK OF HEAVY PRECIPITATION REMAINS POSTED FOR SOUTHEASTERN
ALASKA (OCT 3-7) WHERE THERE CONTINUES TO BE SUPPORT FOR HIGHER 3-DAY AMOUNTS
UPWARDS OF 2 INCHES. SINCE THE START OF SEPTEMBER, THIS PART OF ALASKA HAS
RECEIVED WELL ABOVE NORMAL PRECIPITATION TRIGGERING LANDSLIDES OVER THE
SOUTHEAST, AND ANY ADDITIONAL PRECIPITATION COULD WORSEN THE ANTECEDENT
SATURATED CONDITIONS. EPISODES OF HIGH WINDS ARE ALSO FAVORED, BUT TOOLS ARE
UNSUPPORTIVE OF WIND SPEEDS EXCEEDING HAZARDS CRITERIA ONSHORE OVER THE
SOUTHEAST.
IN THE TROPICS, THE NATIONAL HURRICANE CENTER (NHC) IS CURRENTLY KEEPING CLOSE
WATCH ON TWO TROPICAL DISTURBANCES (INVESTS 93L AND 94L) IN THE WESTERN
ATLANTIC, BOTH WITH GREATER THAN 80% CHANCES OF FORMATION DURING THE NEXT SEVEN
DAYS (AS OF 1:30PM EDT). SINCE EARLIER THIS WEEK, THE TRACKS OF THESE TWO
POTENTIAL SYSTEMS HAVE TRENDED WESTWARD CLOSER TO THE EASTERN SEABOARD, BUT
APPEAR TO CLASH WITH A MEAN FRONTAL BOUNDARY SITUATED JUST OFFSHORE OF THE
COASTAL CAROLINAS AND THE MID-ATLANTIC IN ADVANCE OF STRONG MEAN SURFACE HIGH
OVER THE NORTHEAST LATE IN WEEK1 AND EARLY WEEK-2. WHILE THE GEFS AND ECMWF
ENSEMBLES HAVE COME INTO BETTER AGREEMENT WITH THIS SYNOPTIC SETUP, THERE IS
STILL AMPLE UNCERTAINTY WITH THE EVENTUAL EVOLUTION OF THESE TWO TROPICAL LOWS
AND THE MID-LATITUDE FRONTAL ACTIVITY FAVORED. COMPLICATING THE SITUATION IS
THE POTENTIAL FOR FUJIWHARA INTERACTION BETWEEN THE TWO TROPICAL LOWS, WHERE
SOME SOLUTIONS SHOW INVEST 94L SHIFTING ITS TRACK TO THE EAST AFTER PASSING
JUST NORTH OF THE BAHAMAS, AND POSSIBLY BECOMING ABSORBED BY INVEST 93L (WHICH
IS LIKELY TO FORM EARLIER). EVEN IN THE ABSENCE OF NEARBY BAROCLINICITY, SUCH
DYNAMICS OF PAIRED TROPICAL LOWS ARE REALLY DIFFICULT TO PREDICT PRIOR TO THEIR
FORMATION. HOWEVER, IN CONSIDERATION OF THE WESTWARD TREND OF THE TROPICAL LOW
MEMBERS IN THE LATEST ENSEMBLES, BETTER AGREEMENT BETWEEN THE GEFS AND ECMWF IN
REGARDS TO THE POSITION OF THE MEAN FRONTAL BOUNDARY, AS WELL AS BETTER
AGREEMENT IN THE PETS FOR RAINFALL AMOUNTS EXCEEDING THE 85TH PERCENTILE AND 1
INCH, A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED FROM NORTHERN FLORIDA TO
THE DELMARVA REGION FOR OCT 2-3. ANY HEAVY PRECIPITATION ASSOCIATED WITH INFLUX
OF TROPICAL MOISTURE MAY TRIGGER LOCALIZED FLOODING WITHIN THE HIGHLIGHTED
REGION. ACCOMPANYING THIS HAZARD, A SLIGHT RISK OF HIGH WINDS REMAINS ISSUED
FOR THE SAME PERIOD, AND IS EXPANDED TO INCLUDE MORE OF THE EASTERN CONUS BASED
ON THE STRONGER WIND SIGNALS IN THE ECMWF PET. FOR UPDATES ON THESE TWO
POTENTIAL TROPICAL SYSTEMS, PLEASE CONTINUE TO CHECK WITH THE NATIONAL
HURRICANE CENTER AT: WWW.NHC.NOAA.GOV
FORECASTER: NICK NOVELLA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page