541
FXUS21 KWNC 302057
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 30 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-SAT,
JAN 9-11.
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR MANY AREAS EAST OF THE
ROCKIES EXCLUDING PARTS OF THE NORTHEAST AND SOUTHERN FLORIDA, TUE-SUN, JAN
7-12.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR THE CONUS EAST OF THE ROCKIES
WITH THE EXCEPTION OF THE LOWER RIO GRANGE VALLEY, TUE-MON, JAN 7-13.
MODERATE RISK OF HEAVY SNOW FOR PORTIONS OF THE CENTRAL APPALACHIANS AND GREAT
LAKES, TUE-SAT, JAN 7-11.
SLIGHT RISK OF HEAVY SNOW FOR THE OHIO VALLEY AND NORTHEAST U.S. AS WELL AS
MUCH OF THE MID-ATLANTIC, APPALACHIANS, GREAT LAKES, AND PORTIONS OF THE
TENNESSEE VALLEY AND UPPER MISSISSIPPI VALLEY, TUE-SAT, JAN 7-11.
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, TUE-THU, JAN 7-9.
SLIGHT RISK OF HEAVY PRECIPITATION FOR MUCH OF THE SOUTHERN AND SOUTHEASTERN
COAST OF ALASKA, TUE-SAT, JAN 7-11.
SLIGHT RISK OF HIGH WINDS FOR THE SOUTHERN AND SOUTHEASTERN COAST OF ALASKA,
TUE-SAT, JAN 7-11.
DETAILED SUMMARY
FOR THURSDAY JANUARY 02 - MONDAY JANUARY 06:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY JANUARY 07 - MONDAY JANUARY 13: 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, RUSTLING 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, AS WELL AS
WIDESPREAD 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 THE
NORTHEAST U.S. AND 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 9-11, WHERE THE PETS SHOW THE STRONGEST SIGNAL FOR
REACHING HAZARDOUS TEMPERATURES IN PERCENTILE SPACE AND WHERE BELOW-FREEZING
TEMPERATURES ARE VERY LIKELY. THIS 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,
RESULTING IN WIND CHILLS POTENTIALLY MUCH COLDER THAN ACTUAL AIR TEMPERATURES.
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,
EXTENDING EVEN INTO 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 HIGHER
IMPACTS WITH LOWER SNOWFALL TOTALS. 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 7-11,
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
CENTRAL APPALACHIANS FOR JAN 7-11, AND A SLIGHT RISK OF HEAVY SNOW IS POSTED
FOR THE OHIO VALLEY AND NORTHEAST U.S. AS WELL AS MUCH OF THE MID-ATLANTIC,
APPALACHIANS, AND GREAT LAKES AND PORTIONS OF THE TENNESSEE VALLEY AND UPPER
MISSISSIPPI VALLEY FOR THE SAME PERIOD. FINALLY, A SLIGHT RISK OF HEAVY SNOW IS
POSTED FOR PORTIONS OF THE SOUTHERN PLAINS, TENNESSEE VALLEY, AND LOWER AND
MIDDLE MISSISSIPPI VALLEY FOR JAN 7-9. 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.
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 ALASKAN COAST EXTENDING AS FAR WEST AS THE ALASKAN PENINSULA,
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 7-11 FOR THE AREAS HIGHLIGHTED
ABOVE.
FORECASTER: DANNY BARANDIARAN
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