483
FXUS21 KWNC 311909
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 31 2024
SYNOPSIS: MULTIPLE MODEL ENSEMBLES DEPICT DEEP MID-LEVEL LOW PRESSURE OVER THE
EASTERN CONTIGUOUS U.S. (CONUS) THROUGHOUT THE WEEK-2 PERIOD, AS WELL AS STRONG
MID-LEVEL HIGH PRESSURE OVER THE WESTERN CONUS AND GREENLAND, SETTING UP A
BLOCKING PATTERN THAT IS FAVORED TO FUNNEL ARCTIC AIR INTO THE LOWER 48 EAST OF
THE ROCKIES WITH HIGH CHANCES FOR HAZARDOUS COLD CONDITIONS, AS WELL AS THE
POTENTIAL FOR HEAVY SNOW, PARTICULARLY IN THE GREAT LAKES REGION DUE TO
CONDITIONS FAVORABLE FOR LAKE-EFFECT SNOW. STRONG SURFACE LOW PRESSURE OVER THE
BERING SEA IS FAVORED TO PRODUCE HIGH WINDS AND HEAVY PRECIPITATION FOR THE
SOUTHERN COAST OF ALASKA.
HAZARDS
HIGH RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR THE SOUTHERN APPALACHIANS AND
TENNESSEE VALLEY AS WELL AS MUCH OF THE SOUTHEASTERN U.S. AND PORTIONS OF THE
OHIO VALLEY, MID-ATLANTIC, AND LOWER AND MIDDLE MISSISSIPPI VALLEYS, THU-SUN,
JAN 9-12.
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR MANY AREAS EAST OF THE
ROCKIES EXCLUDING PARTS OF THE NORTHEAST U.S., WED-MON, JAN 8-13.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR THE CONUS EAST OF THE ROCKIES
WITH THE EXCEPTION OF THE LOWER RIO GRANDE VALLEY AND THE NORTHEAST U.S.,
WED-TUE, JAN 8-14.
MODERATE RISK OF HEAVY SNOW FOR PORTIONS OF THE CENTRAL APPALACHIANS AND GREAT
LAKES, WED-SUN, JAN 8-12.
SLIGHT RISK OF HEAVY SNOW FOR THE OHIO VALLEY, APPALACHIANS, AND GREAT LAKES,
AS WELL AS PORTIONS OF THE TENNESSEE VALLEY AND UPPER MISSISSIPPI VALLEY, AND
NON-COASTAL PORTIONS OF THE NORTHEAST U.S. AND MID-ATLANTIC, WED-SUN, JAN 8-12.
SLIGHT RISK OF HEAVY SNOW FOR MUCH OF THE TENNESSEE VALLEY AS WELL AS PORTIONS
OF THE SOUTHEASTERN U.S., LOWER AND MIDDLE MISSISSIPPI VALLEY, AND SOUTHERN
PLAINS, WED-FRI, JAN 8-10.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE NORTHERN AND CENTRAL PLAINS,
WED-SUN, JAN 8-12.
SLIGHT RISK OF HEAVY PRECIPITATION FOR MUCH OF THE SOUTHERN AND SOUTHEASTERN
COAST OF ALASKA, WED-SUN, JAN 8-12.
SLIGHT RISK OF HIGH WINDS FOR THE SOUTHERN AND SOUTHEASTERN COAST OF ALASKA,
WED-SUN, JAN 8-12.
DETAILED SUMMARY
FOR FRIDAY JANUARY 03 - TUESDAY JANUARY 07:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY JANUARY 08 - TUESDAY JANUARY 14: MODEL ENSEMBLES ARE IN VERY GOOD
AGREEMENT REGARDING DEPICTION OF A DEEPENING TROUGH OVER THE EASTERN CONUS
DURING THE WEEK-2 PERIOD, AS WELL AS AMPLIFIED RIDGING OVER GREENLAND AND THE
WEST COAST, RESULTING IN A LONG FETCH OF NORTHERLY WINDS FROM THE CANADIAN
ARCTIC THROUGH MUCH OF THE CENTRAL AND EASTERN CONUS LEADING TO HIGH POTENTIAL
FOR HAZARDOUS COLD ACROSS MUCH OF THE LOWER 48 EAST OF THE ROCKIES. AT THE
OUTSET OF WEEK-2 MODEL GUIDANCE INDICATES NEARLY UNIVERSAL SUB-FREEZING
TEMPERATURES FOR MUCH OF THE CENTRAL AND EASTERN CONUS WITH THE ONLY EXCEPTIONS
BEING SOUTHERN PORTIONS OF BOTH TEXAS AND THE FLORIDA PENINSULA. AS WEEK-2
PROGRESSES, MODELS FAVOR A CONTINUED SPREAD OF COLD AIR INTO THE SOUTHEAST U.S.
WITH THE GREATEST POTENTIAL FOR HAZARDOUS COLD TO OCCUR DURING THE MIDDLE OF
WEEK-2. THE ECMWF AND GEFS PROBABILISTIC EXTREMES TOOLS (PETS) BOTH INDICATE AT
LEAST A 20% CHANCE OF LOW TEMPERATURES FALLING BELOW THE 15TH PERCENTILE
THROUGHOUT WEEK-2 FOR MOST OF THE CONUS EAST OF THE ROCKIES EXCEPT FOR THE
NORTHEAST U.S., AS WELL AS A WIDESPREAD COVERAGE OF GREATER THAN 40%
PROBABILITIES FOR THE EARLY AND MIDDLE PORTION OF WEEK-2 FOR NEARLY THE SAME
AREAS AS LISTED ABOVE (WITH THE EXCEPTION OF MUCH OF THE SOUTHERN PLAINS).
ADDITIONALLY, A HIGH RISK (AT LEAST A 60% CHANCE) OF MUCH BELOW-NORMAL
TEMPERATURES IS POSTED FOR THE SOUTHERN APPALACHIANS AND TENNESSEE VALLEY AS
WELL AS MUCH OF THE SOUTHEASTERN U.S. AND PORTIONS OF THE OHIO VALLEY,
MID-ATLANTIC, AND LOWER AND MIDDLE MISSISSIPPI VALLEYS FOR JAN 9-12, WHERE THE
PETS SHOW THE STRONGEST SIGNAL FOR REACHING HAZARDOUS TEMPERATURES IN
PERCENTILE SPACE AND WHERE WELL-BELOW FREEZING TEMPERATURES ARE VERY LIKELY.
THE POTENTIAL FOR A HARD FREEZE EXTENDS WELL INTO THE FLORIDA PENINSULA, WHICH
COULD NEGATIVELY IMPACT CITRUS PRODUCTION IN THE STATE. IN ADDITION TO THE VERY
COLD TEMPERATURES MULTIPLE MODELS SHOW A BROAD AREA WITH POSSIBLY TIGHT
PRESSURE GRADIENT OVER MUCH OF THE EASTERN CONUS THROUGHOUT THE WEEK, WHICH
COULD RESULT IN WIDESPREAD BREEZY CONDITIONS AND VERY LOW WIND CHILLS. TODAY’S
ECMWF AND CMCE PETS INDICATE THAT WINDS SPEEDS HAVE AT LEAST A 20% CHANCE OF
EXCEEDING THE 85TH PERCENTILE OVER PORTIONS OF THE NORTHERN AND CENTRAL PLAINS,
THEREFORE A SLIGHT RISK FOR HIGH WINDS IS POSTED FOR JAN 8-12, DURING WHICH THE
PETS ARE IN STRONGEST AGREEMENT.
IN ADDITION TO THE ANTICIPATED BITTER COLD, NORTHERLY WINDS FROM CANADA AND
SURFACE LOW PRESSURE OVER THE CANADIAN MARITIMES FAVORS INCREASED CHANCES FOR
HEAVY SNOW FOR MUCH OF THE EASTERN CONUS THROUGH THE MIDDLE OF WEEK-2. THE
INCREASED RISK FOR HEAVY SNOW EVEN EXTENDSINTO THE LOWER MISSISSIPPI VALLEY AND
SOUTHERN PLAINS EARLY IN THE FORECAST PERIOD AS A COLD FRONT MOVING OVER THE
GREAT PLAINS CAN TAP INTO MOISTURE OFF THE GULF OF MEXICO. ECMWF ENSEMBLE
SNOWFALL TOTALS EXCEED 1.5 INCHES OVER THE DALLAS METRO REGION, EXTENDING INTO
ARKANSAS AND THE TENNESSEE VALLEY EARLY IN WEEK-2. WHILE SIGNIFICANT
ACCUMULATIONS ARE NOT EXPECTED, THESE REGIONS ARE OFTEN ILL-EQUIPPED TO HANDLE
SNOWY CONDITIONS, RESULTING IN POTENTIALLY HIGHER IMPACTS WITH LOWER SNOWFALL
TOTALS. IT SHOULD BE NOTED THAT THIS SOUTHERN AREA HIGHLIGHTED FOR THE RISK OF
HEAVY SNOW COULD EXPERIENCE A VARIETY OF MIXED PRECIPITATION TYPES INSTEAD OF
ALL SNOW. REGARDLESS OF PRECIPITATION TYPE, A SLIGHT RISK OF HEAVY SNOW IS
POSTED FOR PORTIONS OF THE SOUTHERN PLAINS, TENNESSEE VALLEY, AND LOWER AND
MIDDLE MISSISSIPPI VALLEY FOR JAN 8-10. GREATER SNOW ACCUMULATIONS ARE FAVORED
FOR THE NORTHEASTERN CONUS, PARTICULARLY FOR AREAS OF THE GREAT LAKES FAVORED
FOR LAKE-EFFECT SNOW. WHILE THERE IS NOT MUCH SIGNAL FROM THE GEFS PET FOR HIGH
SNOW WATER EQUIVALENT TOTALS, MODEL ENSEMBLE TOTALS FOR SNOWFALL FROM THE ECMWF
ARE QUITE BULLISH NEAR THE GREAT LAKES AND OVER THE APPALACHIANS FROM JAN 8-12,
AFTER WHICH SNOWFALL TOTALS TAPER OFF BELOW HAZARDOUS THRESHOLDS. A MODERATE
RISK OF HEAVY SNOW IS POSTED FOR THE UPPER PENINSULA AND WESTERN SHORE OF
MICHIGAN, AS WELL AS THE SOUTHERN SHORES OF LAKES ERIE AND ONTARIO AND THE
ALLEGHENY FRONT FOR JAN 8-12, AND A SLIGHT RISK OF HEAVY SNOW IS POSTED FOR THE
OHIO VALLEY, APPALACHIANS, AND GREAT LAKES, AS WELL AS PORTIONS OF THE
TENNESSEE VALLEY AND UPPER MISSISSIPPI VALLEY, AND NON-COASTAL PORTIONS OF THE
NORTHEAST U.S. AND MID-ATLANTIC FOR THE SAME PERIOD.
AMPLIFIED RIDGING OVER THE WEST COAST AND STRONG SURFACE LOW PRESSURE OVER THE
BERING SEA THROUGHOUT WEEK-2 FAVORS STRONG MOIST ONSHORE FLOW INTO THE SOUTHERN
COAST OF ALASKA. THE ECMWF AND GEFS PETS BOTH INDICATE A 20% CHANCE OF 3-DAY
RAINFALL TO EXCEED THE 85TH PERCENTILE AND 2-3 INCHES FOR MUCH OF THE ALASKAN
COAST FROM THE KENAI PENINSULA EAST ALONG THE COAST AND DOWN THROUGH THE
PANHANDLE. MODEL OUTPUT ALSO INDICATES THE POTENTIAL FOR WINDS EXCEEDING 40MPH
ALONG THE SAME STRETCH OF ALASKAN COAST, ALTHOUGH THE SIGNAL FOR BOTH HEAVY
PRECIPITATION AND HIGH WINDS TAILS OFF TOWARDS THE END OF THE WEEK-2 PERIOD.
THEREFORE, SLIGHT RISKS OF HEAVY PRECIPITATION AND HIGH WINDS ARE POSTED FOR
JAN 8-12 FOR THE AREAS HIGHLIGHTED ABOVE.
FORECASTER: DANNY BARANDIARAN
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