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FXUS21 KWNC 251924
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SEPTEMBER 25 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 CURRENTLY MONITORING TWO
TROPICAL SYSTEMS OVER THE WESTERN ATLANTIC (TROPICAL STORM HUMBERTO AND
DISTURBANCE AL94). 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 NEAR THE SOUTHEAST COAST CANNOT
BE RULED OUT FOR MUCH OF THE EAST COAST EARLY IN THE PERIOD.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION ALONG THE SOUTHEAST COAST, FRI-SAT, OCT 3-4.
SLIGHT RISK OF HIGH WINDS FOR MUCH OF THE MIDDLE AND SOUTHERN ATLANTIC STATES,
FRI-SAT, OCT 3-4.
SLIGHT RISK OF HEAVY PRECIPITATION FOR SOUTHEAST ALASKA, FRI-TUE, OCT 3-7.
RAPID ONSET DROUGHT (ROD) POSSIBLE FOR PARTS OF TEXAS AND LOUISIANA.
DETAILED SUMMARY
FOR SUNDAY SEPTEMBER 28 - THURSDAY OCTOBER 02:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY OCTOBER 03 - THURSDAY OCTOBER 09: BOTH THE 0Z GEFS AND ECMWF 500-HPA
MEAN HEIGHT FORECASTS ARE IN GOOD AGREEMENT FAVORING AN AMPLIFIED ANOMALOUS
RIDGE CENTERED TO THE SOUTHEAST OF HUDSON BAY IN CANADA, WITH A PAIR OF MEAN
LONGWAVE TROUGHS OVER THE NORTHEASTERN PACIFIC AND THE NORTHWESTERN ATLANTIC
TOWARDS THE END 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. OUTLOOK CONFIDENCE FOR
UNSEASONABLY WARM TEMPERATURES IS INCREASED 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 THE POSSIBILITY OF 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 ABOVE-NORMAL TEMPERATURES FAVORED IN THE RAW TOOLS FOR MOST OF THE 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 FARTHER 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 PRECIPITATION AMOUNTS TO EXCEED THE 85TH HISTORICAL
PERCENTILE AND 1.0-1.5 INCHES OVER THE PACIFIC NORTHWEST, WITH 2-3 INCH AMOUNTS
INDICATED ACROSS SOUTHEAST ALASKA. FOR THE PACIFIC NORTHWEST, THESE PREDICTED
PRECIPITATION TOTALS FALL SHORT OF HAZARDOUS THRESHOLDS FOR THIS TIME OF YEAR,
BUT FOR SOUTHEAST ALASKA, A SLIGHT RISK OF HEAVY PRECIPITATION REMAINS POSTED,
VALID OCT 3-7. 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 SYSTEMS (AL94 AND TROPICAL STORM UMBERTO) IN THE WESTERN
ATLANTIC. THE FIRST SYSTEM, AL94, IS CURRENTLY (2PM EDT SEPT 25) A DISORGANIZED
CLUSTER OF SHOWERS AND THUNDERSTORMS IN THE VICINITY OF HISPANIOLA. A LOW
PRESSURE CENTER IS FORECAST TO FORM WITHIN THIS TROPICAL WAVE AS IT MOVES
TOWARDS THE SOUTHEASTERN BAHAMAS, WITH NHC ESTIMATING A 90% CHANCE OF TROPICAL
CYCLONE DEVELOPMENT WITHIN THE NEXT 7 DAYS. THE SECOND SYSTEM, TROPICAL STORM
HUMBERTO, IS CURRENTLY (2PM AST) 465 MILES EAST-NORTHEAST OF THE NORTHERN
LEEWARD ISLANDS AND IS EXPECTED TO BECOME A HURRICANE IN A DAY OR SO. MOST
MODEL SOLUTIONS AT THIS TIME RECURVE HUMBERTO WELL EAST OF THE ATLANTIC COAST,
PROBABLY NEAR 70W LONGITUDE. DETERMINISTIC AND ENSEMBLE MEAN MODELS (FROM THE
GEFS AND ECENS) PRESENT A WIDE ARRAY OF POTENTIAL SCENARIOS. ENSEMBLE GUIDANCE
DEPICTS WIDELY DIVERGING TRACKS IN THE POTENTIAL LOW PRESSURE CENTER AS THE
SYSTEM HEADS TOWARDS THE CAROLINAS. THE MOST RECENT DETERMINISTIC GFS RUN (12Z)
IS FASTER OVERALL COMPARED TO THE EARLIER 0Z AND 6Z RUNS. ANOTHER COMPLICATING
FACTOR IS THE PREDICTED PRESENCE OF A STATIONARY FRONT JUST OFF THE CAROLINA
COAST, WHICH COULD INFLUENCE THE PATH AND/OR STRENGTH OF AL94. THE FINAL MAJOR
SOURCE OF UNCERTAINTY IS RELATED TO THE SO-CALLED “FUJIWHARA EFFECT”, WHERE TWO
REASONABLY CLOSE TROPICAL SYSTEMS CAN INTERACT WITH, AND DUMBBELL AROUND EACH
OTHER, WITH THE LARGER SYSTEM BEING THE PRIMARY DRIVER OF THIS EFFECT. THIS
COULD HAVE A SIGNIFICANT IMPACT ON THE TRACK OF EITHER SYSTEM. STRONG MEAN
SURFACE HIGH PRESSURE OVER THE NORTHEAST LATE IN WEEK-1 IS EXPECTED TO MAINTAIN
MOIST, NORTHEASTERLY ONSHORE FLOW ALONG THE EASTERN SEABOARD FROM NEW JERSEY
SOUTHWARD TO FLORIDA. WITHIN THIS REGION, TWO HAZARDS ARE POSTED FOR OCT 3-4,
SINCE IT IS STILL UNCLEAR AS TO HOW LONG THE PHYSICAL INTERACTIONS BETWEEN THE
TROPICAL SYSTEMS AND THE STATIONARY FRONT WILL LAST BEYOND WEEK-1. THE FIRST
HAZARD AREA IS FOR A SLIGHT RISK OF HEAVY PRECIPITATION ALONG THE SOUTHEAST
COAST, FROM NEAR THE VIRGINIA TIDEWATER AREA TO SOUTHERN FLORIDA, WHERE 1-INCH
OF PRECIPITATION COULD FALL WITHIN A 3-DAY PERIOD. THE SECOND HAZARD POSTED IS
FOR A SLIGHT RISK OF HIGH WINDS (20 MPH, GUSTS TO 30 MPH) FOR MOST OF THE
MID-ATLANTIC AND SOUTHERN ATLANTIC STATES. FOR UPDATES ON THESE TWO TROPICAL
SYSTEMS, PLEASE CONTINUE TO CHECK WITH THE NATIONAL HURRICANE CENTER AT:
WWW.NHC.NOAA.GOV
ACROSS A LARGE PORTION 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
HISTORICAL DISTRIBUTION. ABOVE-NORMAL TEMPERATURES PREDICTED FOR THE NEXT TWO
WEEKS, AND GENERALLY LIGHT OR NO PRECIPITATION INDICATES THE POTENTIAL FOR
RAPID ONSET DROUGHT (ROD) ACROSS THIS REGION.
FORECASTER: ANTHONY ARTUSA
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