926
FXUS21 KWNC 291940
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST NOVEMBER 29 2025
SYNOPSIS: DYNAMICAL MODELS ARE IN GOOD AGREEMENT REGARDING ANOMALOUS MID-LEVEL
LOW PRESSURE ACROSS THE EASTERN CONTIGUOUS U.S. (CONUS) AT THE OUTSET OF
WEEK-2. ENHANCED CHANCES OF HEAVY SNOW AND BELOW-NORMAL TEMPERATURES ARE
FAVORED TO PERSIST ACROSS PARTS OF THE GREAT LAKES AND NORTHEAST. HOWEVER,
DIVERGING MODEL SOLUTIONS REGARDING THE AMPLIFICATION OF THE MID-LEVEL PATTERN
REDUCES CONFIDENCE TOWARD THE MIDDLE OF THE PERIOD. MID-LEVEL HIGH (LOW)
PRESSURE FORECAST ACROSS THE WEST COAST OF THE CONUS (ALASKA) FAVORS A TIGHT
PRESSURE GRADIENT AND ENHANCED ONSHORE FLOW ACROSS MUCH OF WESTERN NORTH
AMERICA. WHILE PRECIPITATION SIGNALS IN THE MODEL GUIDANCE ARE MARGINAL, THERE
IS AN INCREASED CHANCE FOR HEAVY SNOW ACROSS THE NORTHERN CASCADES AND NORTHERN
ROCKIES, ALONG WITH ENHANCED WIND SPEEDS OVER SOUTHEAST ALASKA.
HAZARDS
SLIGHT RISK OF HEAVY SNOW ACROSS THE NORTHERN CASCADES, SUN-WED, DEC 7-10.
SLIGHT RISK OF HEAVY SNOW ACROSS THE NORTHERN ROCKIES, SUN-WED, DEC 7-10.
SLIGHT RISK OF HEAVY SNOW ACROSS THE UPPER PENINSULA OF MICHIGAN AND WESTERN
PORTIONS OF LOWER MICHIGAN, SUN-TUE, DEC 7-9.
SLIGHT RISK OF HEAVY SNOW ACROSS PORTIONS OF THE INTERIOR NORTHEAST AND
MID-ATLANTIC, AND CENTRAL APPALACHIANS, SUN-TUE, DEC 7-9.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE UPPER
MISSISSIPPI VALLEY AND WESTERN GREAT LAKES, SUN-TUE, DEC 7-9.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF UPSTATE NEW
YORK AND NORTHERN NEW ENGLAND, SUN-TUE, DEC 7-9.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE LOWER MISSISSIPPI
VALLEY, TENNESSEE VALLEY, AND SOUTHEAST, SUN-MON, DEC 7-8.
SLIGHT RISK OF HIGH WINDS ACROSS SOUTHEASTERN ALASKA, SUN-THU, DEC 7-11.
DETAILED SUMMARY
FOR TUESDAY DECEMBER 02 - SATURDAY DECEMBER 06:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SUNDAY DECEMBER 07 - SATURDAY DECEMBER 13: A DEEP 500-HPA TROUGH IS
FORECAST ACROSS THE EASTERN U.S. AT THE BEGINNING OF WEEK-2. THE 0Z ECMWF AND
CANADIAN ENSEMBLES ARE MORE AMPLIFIED WITH THIS FEATURE COMPARED TO THE 0Z
GEFS, AND THE GEFS IS ALSO QUICK TO DE-AMPLIFY THE TROUGH BY THE SECOND HALF OF
THE PERIOD. THE TROUGH FAVORS A PERSISTENCE OF CYCLONIC FLOW AND PULSES OF
NORTHERN STREAM ENERGY ACROSS THE NORTH-CENTRAL AND NORTHEASTERN CONUS
RESULTING IN PERIODIC CHANCES OF HEAVY SNOW, BOTH DIRECTLY ASSOCIATED WITH THE
SHORTWAVE ENERGY, AND LAKE EFFECT SNOW. THEREFORE, SLIGHT RISKS OF HEAVY SNOW
ARE POSTED ACROSS PORTIONS OF UPPER MICHIGAN AND WESTERN PORTIONS OF LOWER
MICHIGAN, ALONG WITH THE INTERIOR NORTHEAST, MID-ATLANTIC, AND EXTENDING ALONG
THE ALLEGHENY FRONT, DEC 7-9. THE UNCALIBRATED 0Z ECMWF ENSEMBLE DEPICTS AT
LEAST A 20 PERCENT CHANCE 3-DAY SNOWFALL TOTALS EXCEED 4-INCHES OVER MOST OF
THESE HIGHLIGHTED AREAS.
ALONG WITH THE POTENTIAL FOR SNOW, IS THE POSSIBILITY OF MUCH BELOW-NORMAL
TEMPERATURES. THE ECMWF PROBABILISTIC EXTREMES TOOL (PET) DEPICTS PARTS OF THE
UPPER MISSISSIPPI VALLEY, GREAT LAKES, AND NORTHEAST HAVING A 30-50 PERCENT
CHANCE MINIMUM TEMPERATURES DROP BELOW THE 10TH CLIMATOLOGICAL PERCENTILE. THIS
WOULD CORRESPOND TO ELEVATED CHANCES OF SUBZERO TEMPERATURES OVER PORTIONS OF
THE UPPER MISSISSIPPI VALLEY AND THE INTERIOR NORTHEAST, WITH NEGATIVE TEENS
POSSIBLE ACROSS NORTHERN MINNESOTA AND NORTH DAKOTA. TAKING WIND CHILL INTO
ACCOUNT, SOME OF THESE AREAS MAY REACH NWS COLD ADVISORY CRITERIA SUPPORTING A
SLIGHT RISK FOR MUCH BELOW NORMAL TEMPERATURES, DEC 7-9. THIS IS MAINLY BASED
ON THE ECMWF ENSEMBLE GUIDANCE, AS THE GEFS IS NOTABLY WARMER WITH A MORE
LIMITED SIGNAL FOR HAZARDOUS COLD IN ITS CORRESPONDING PET GIVEN QUICKER
WEAKENING OF THE TROUGH IN THE EAST. WHILE THE ECMWF WOULD SUPPORT A LONGER
DURATION OF THE MUCH BELOW NORMAL TEMPERATURE HAZARD, THE LESS AMPLIFIED GEFS
FURTHER REDUCES CONFIDENCE LATER IN WEEK-2.
THE 0Z GEFS, ECWMF, AND CANADIAN ENSEMBLES DEPICT ANOTHER SOUTHERN STREAM
SYSTEM AROUND THE BEGINNING OF WEEK-2, WITH ASSOCIATED PRECIPITATION EXTENDING
FROM THE LOWER MISSISSIPPI VALLEY TO THE SOUTHERN MID-ATLANTIC AND SOUTHEAST
COASTS. THE GEFS AND ECMWF PETS BOTH INDICATE SOME AREAS HAVING AT LEAST A 20
PERCENT CHANCE 3-DAY PRECIPITATION TOTALS EXCEED THE 85TH CLIMATOLOGICAL
PERCENTILE AND 1-INCH. THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION IS
POSTED ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY, TENNESSEE VALLEY, AND
SOUTHEAST, DEC 7-8, CORRESPONDING WITH THE STRONGEST 24-HOUR PRECIPITATION
SIGNALS IN THE UNCALIBRATED GUIDANCE. GIVEN THAT MANY OF THESE AREAS ARE UNDER
DROUGHT CONDITIONS, ANY PRECIPITATION MAY END UP BEING BENEFICIAL RATHER THAN
HAZARDOUS.
RIDGING IS FORECAST ALONG THE WEST COAST OF THE CONUS DURING WEEK-2, WITH
TROUGHING ACROSS ALASKA. THIS RESULTS IN A STRONG MID-LEVEL PRESSURE GRADIENT
OVER THE WEST COAST, AND THE GEFS AND ECMWF PETS INDICATE AN ELEVATED SIGNAL
FOR ENHANCED PRECIPITATION ACROSS THE PACIFIC NORTHWEST DURING THE PERIOD.
HOWEVER, THE CHANCES FOR INTEGRATED VAPOR TRANSPORT (IVT) TO EXCEED 250 KG/M/S
ARE LOW THROUGH ABOUT DAY-10 (DEC 9) AND 24-HOUR PRECIPITATION TOTALS IN THE 0Z
GEFS AND ECMWF ENSEMBLES ARE GENERALLY UNDER 1-INCH. THEREFORE, NO RELATED
PRECIPITATION HAZARD IS POSTED AT THIS TIME, BUT THIS WILL CONTINUE TO BE
MONITORED. THE BIGGER CONCERN IS LIKELY INCREASED CHANCES FOR HEAVY SNOW ACROSS
THE NORTHERN CASCADES AND NORTHERN ROCKIES WHERE THE GEFS AND ECMWF ENSEMBLES
DEPICT ENHANCED PROBABILITIES FOR 3-DAY SNOWFALL TOTALS EXCEEDING 12-INCHES
SUPPORTING SLIGHT RISKS FOR HEAVY SNOW OVER THESE AREAS, DEC 7-10.
BELOW-NORMAL TEMPERATURES ARE LIKELY ACROSS ALASKA ASSOCIATED WITH TROUGHING
OVER THE STATE, ALTHOUGH NWS COLD ADVISORY CRITERIA IS UNLIKELY TO BE REACHED.
PERIODS OF HEAVY PRECIPITATION AND HIGH WINDS ARE LIKELY ACROSS SOUTHEAST
ALASKA DUE TO ENHANCED ONSHORE FLOW. WHILE PRECIPITATION TOTALS IN THE PETS AND
UNCALIBRATED GUIDANCE DO NOT REACH HAZARDS THRESHOLDS, THE ECMWF PET DEPICTS
PARTS OF THE REGION HAVING AT LEAST A 20 PERCENT CHANCE WIND SPEEDS EXCEED
40-MPH ASSOCIATED WITH MEAN SURFACE LOW PRESSURE OVER THE GULF OF ALASKA.
THEREFORE, A SLIGHT RISK FOR HIGH WINDS IS POSTED ACROSS SOUTHEASTERN ALASKA,
DEC 7-11.
FORECASTER: THOMAS COLLOW
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