780
FXUS21 KWNC 281853
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST NOVEMBER 28 2024
SYNOPSIS: A REINFORCING SHOT OF COLD AIR IS LIKELY TO MOVE INTO THE EASTERN
CONTIGUOUS U.S. (CONUS) NEAR THE START OF THE WEEK-2 PERIOD WITH DEEPENING
MID-LEVEL LOW-PRESSURE. THE ADDITIONAL COLD AIR ADVECTION INTO THE NORTHEASTERN
CONUS MAY CONTINUE TO PROMOTE LAKE EFFECT SNOW OFF THE GREAT LAKES. ONSHORE
FLOW INTO WESTERN NORTH AMERICA EARLY IN WEEK-2 MAY IMPACT PORTIONS OF THE
NORTHWEST BRINGING CHANCES FOR HEAVY PRECIPITATION. WHILE IN SOUTHEASTERN
ALASKA, REPEATED CHANCES FOR HEAVY PRECIPITATION ARE POSSIBLE THROUGHOUT
WEEK-2.
HAZARDS
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR INTERIOR NEW ENGLAND,
SAT-TUE, DEC 7-10.
SLIGHT RISK OF HEAVY SNOW FOR FAVORED LAKE EFFECT SNOW BELTS AND ALONG THE
ALLEGHENY FRONT, FRI-MON, DEC 6-9.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF WESTERN WASHINGTON, FRI-SUN,
DEC 6-8.
SLIGHT RISK OF HEAVY SNOW FOR PORTIONS OF THE NORTHERN CASCADES AND NORTHERN
ROCKIES, FRI-SUN, DEC 6-8.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS SOUTH-CENTRAL AND SOUTHEAST
MAINLAND ALASKA AND SOUTHEAST ALASKA, FRI-THU, DEC 6-12.
DETAILED SUMMARY
FOR SUNDAY DECEMBER 01 - THURSDAY DECEMBER 05:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY DECEMBER 06 - THURSDAY DECEMBER 12: NEGATIVE 500-HPA HEIGHT
ANOMALIES AND TROUGHING CONTINUE TO BE FORECAST FOR THE EASTERN CONUS DURING
MUCH OF THE WEEK-1 AND 2 PERIOD. THIS TROUGH WILL BE REINFORCED WITH ANOTHER
ROUND OF NEGATIVE HEIGHT ANOMALIES MOVING SOUTH FROM THE ARCTIC AT THE START OF
WEEK-2 AND BRING ENHANCED CHANCES FOR MUCH BELOW-NORMAL TEMPERATURES TO
PORTIONS OF THE NORTHEAST. MINIMUM TEMPERATURES FROM THE RAW ECENS ARE FORECAST
TO BE IN THE SINGLE DIGITS. SIMILARLY, THE GEFS PROBABILISTIC EXTREMES TOOL
(PET) INDICATES 20-40% CHANCES FOR TEMPERATURES TO FALL INTO SINGLE DIGITS AND
BELOW THE 15TH CLIMATOLOGICAL PERCENTILE. THEREFORE, A SLIGHT RISK OF MUCH
BELOW-NORMAL TEMPERATURES IS POSTED FOR DEC 7-10 ACROSS THE INTERIOR PORTIONS
OF NEW ENGLAND.
THE BROAD MID-LEVEL TROUGH ACROSS THE NORTHEASTERN CONUS CONTINUES TO BRING
CHANCES FOR LAKE EFFECT SNOW OFF THE GREAT LAKES. WHILE, THE ENVIRONMENT DOES
NOT APPEAR TO BE AS FAVORABLE FOR HEAVY LAKE EFFECT INTO WEEK-2 AS IN THE
COMING WEEK, THERE CONTINUES TO BE SOME SIGNALS FOR SHORTWAVE TROUGHS TO MOVE
THROUGH THE REGION THAT MAY PROMOTE ADDITIONAL SNOW CHANCES. A SLIGHT RISK OF
HEAVY SNOW IS POSTED FOR DOWNWIND OF THE GREAT LAKES AND ACROSS THE ALLEGHENY
FRONT FOR DEC 6-9.
ALONG THE WEST COAST, ONSHORE FLOW AND HEAVY PRECIPITATION IS FORECAST DURING
WEEK-1 TO IMPACT PORTIONS OF BRITISH COLUMBIA. BY THE BEGINNING OF WEEK-2 THE
PRECIPITATION CHANCES MAY SHIFT SOUTH INTO PORTIONS OF THE NORTHWEST. THE ECENS
PET INDICATES AT LEAST A 20% CHANCE OF 3-DAY PRECIPITATION AMOUNTS EXCEEDING
THE 85TH CLIMATOLOGICAL PERCENTILE AND 2 INCHES. THIS IS SUPPORTED BY THE
INTEGRATED WATER VAPOR (IVT) TRANSPORT WHICH FORECAST STRONG CHANCES FOR MORE
THAN 250 KG/M/S INTO PORTIONS OF WESTERN WASHINGTON. MEANWHILE, THE GEFS PET
INDICATES AT LEAST A 20% CHANCE OF 3 DAY SNOW WATER EQUIVALENT (SWE) TO EXCEED
THE 85TH PERCENTILE AND 0.5 INCHES ACROSS PORTIONS OF THE NORTHERN ROCKIES.
THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED FOR COASTAL PORTIONS
OF WESTERN WASHINGTON FOR DEC 6-8. ASSOCIATED SLIGHT RISKS OF HEAVY SNOW ARE
FORECAST PARTS OF THE NORTHERN CASCADES AND NORTHERN ROCKIES FOR THE SAME
PERIOD.
IN THE SOUTH-CENTRAL CONUS SOME TOOLS SHOW ENHANCED CHANCES FOR HEAVY
PRECIPITATION DURING WEEK-2. AT THIS TIME THERE IS CONSIDERABLE UNCERTAINTY
ABOUT THIS POTENTIAL, AND EVEN THE MOST AGGRESSIVE TOOLS ARE NOT REMARKABLY
WETTER THAN HAZARDS THRESHOLDS, SO FOR NOW, NO HAZARD IS POSTED.
GUIDANCE REMAINS FAIRLY ROBUST WITH THE POTENTIAL FOR A SERIES OF STRONG LOW
PRESSURE SYSTEMS TO TRACK ACROSS OR NEAR THE GULF OF ALASKA. THE TIMING,
STRENGTH, AND TRACK OF INDIVIDUAL STORM SYSTEMS IS HIGHLY UNCERTAIN, BUT A
LARGE-SCALE PATTERN FAVORABLE FOR PERIODS OF STORMY WEATHER IS EXPECTED ALONG
PARTS OF THE SOUTHERN TIER OF ALASKA THROUGHOUT WEEK-2. FOR THIS REASON, A
SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED FOR SOUTH-CENTRAL AND SOUTHEASTERN
ALASKA FOR THE ENTIRETY OF THE PERIOD. IN ADDITION, STRONG WINDS WILL BE
POSSIBLE AT TIMES ACROSS THE ENTIRE SOUTHERN TIER OF THE STATE, INCLUDING PARTS
OF THE ALEUTIANS. RIGHT NOW, HOWEVER, IT APPEARS THAT DANGEROUSLY HIGH WINDS
WILL PRIMARILY AFFECT OFFSHORE AREAS, SO NO HIGH WIND HAZARD IS POSTED, BUT
THIS SITUATION WILL NEED TO BE CLOSELY MONITORED FOR SIGNS THAT STRONGER WINDS
MAY OCCUR INLAND.
FORECASTER: RYAN BOLT
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