028
FXUS21 KWNC 011930
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 01 2025
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 FOR THE GREAT LAKES REGION AS WELL AS PORTIONS OF THE
SOUTHERN PLAINS ACROSS TO THE MID-ATLANTIC REGION. 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 MUCH OF THE SOUTHEASTERN U.S.
AND PORTIONS OF THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS, THU-SAT, JAN 9-11.
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR THE SOUTHEASTERN U.S.,
TENNESSEE AND OHIO VALLEYS, AND THE APPALACHIANS, AS WELL AS MUCH OF THE
MID-ATLANTIC, AND LOWER AND MIDDLE MISSISSIPPI VALLEY, AND PORTIONS OF THE
GREAT LAKES, AND CENTRAL AND SOUTHERN PLAINS, THU-SUN, JAN 9-12.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR MUCH OF THE CENTRAL AND
EASTERN CONUS WITH THE EXCEPTION OF THE WESTERN GREAT PLAINS AND THE NORTHEAST
U.S., THU-TUE, JAN 9-14.
SLIGHT RISK OF HEAVY SNOW DOWNWIND OF LAKES ERIE AND ONTARIO AND ALONG THE
ALLEGHENY FRONT, THU-MON, JAN 9-13.
SLIGHT RISK OF HEAVY SNOW FOR MUCH OF THE TENNESSEE VALLEY AS WELL AS PORTIONS
OF THE MID-ATLANTIC, SOUTHEASTERN U.S., LOWER AND MIDDLE MISSISSIPPI VALLEY,
AND SOUTHERN PLAINS, THU-FRI, JAN 9-10.
SLIGHT RISK OF HEAVY SNOW FOR PORTIONS OF THE NORTHERN AND CENTRAL PLAINS,
THU-MON, JAN 9-13.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE NORTHERN AND CENTRAL PLAINS,
THU-MON, JAN 9-13.
SLIGHT RISK OF HEAVY PRECIPITATION FOR MUCH OF THE SOUTHERN AND SOUTHEASTERN
COAST OF ALASKA, THU-MON, JAN 9-13.
SLIGHT RISK OF HIGH WINDS FOR THE SOUTHERN AND SOUTHEASTERN COAST OF ALASKA,
THU-MON, JAN 9-13.
DETAILED SUMMARY
FOR SATURDAY JANUARY 04 - WEDNESDAY JANUARY 08:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY JANUARY 09 - WEDNESDAY JANUARY 15: MODEL ENSEMBLES CONTINUE TO BE
IN VERY GOOD AGREEMENT REGARDING DEPICTION OF A DEEP 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. TODAY’S
MODEL GUIDANCE FAVORS A WEAKENING OF THE BLOCKING RIDGES LATER IN WEEK-2 AND A
GRADUAL MODERATION OF THE INTRUDING ARCTIC AIRMASS. NONETHELESS, THIS IS LIKELY
TO BE A VERY IMPACTFUL SURGE OF ARCTIC AIR NEAR THE PEAK OF WINTER FOR MUCH OF
THE CENTRAL AND EASTERN CONUS. THE ECMWF AND GEFS PROBABILISTIC EXTREMES TOOLS
(PETS) BOTH INDICATE AT LEAST A 20% CHANCE OF LOW TEMPERATURES FALLING BELOW
THE 15TH PERCENTILE FOR JAN 9-14 FOR MOST OF THE CONUS EAST OF 100W EXCEPT FOR
THE NORTHEAST U.S., AS WELL AS A WIDESPREAD COVERAGE OF GREATER THAN 40%
PROBABILITIES FOR JAN 9-12 OVER NEARLY THE SAME AREAS AS LISTED ABOVE (WITH THE
EXCEPTION OF THE UPPER MISSISSIPPI VALLEY AND GREAT LAKES). ADDITIONALLY, A
HIGH RISK (AT LEAST A 60% CHANCE) OF MUCH BELOW-NORMAL TEMPERATURES IS POSTED
FOR MUCH OF THE SOUTHEASTERN U.S. AS WELL AS PORTIONS OF THE SOUTHERN
APPALACHIANS, AND TENNESSEE AND LOWER MISSISSIPPI VALLEYS FOR JAN 9-11, 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 9-13, 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 PORTIONS OF THE CENTRAL AND EASTERN CONUS THROUGH THE MIDDLE OF
WEEK-2. THE INCREASED RISK FOR HEAVY SNOW EVEN EXTENDS INTO THE SOUTHERN TIER
EARLY IN THE FORECAST PERIOD AS A SURFACE LOW IS FAVORED TO TRACK FROM THE
SOUTHERN PLAINS TO THE MID-ATLANTIC, TAPPING INTO MOISTURE OFF THE GULF OF
MEXICO. ECMWF RAW ENSEMBLE SNOWFALL TOTALS HAVE CONSISTENTLY INDICATED MEAN
ACCUMULATIONS NEAR 2”, AND SEVERAL RECENT DETERMINISTIC GFS RUNS DEPICT HEAVY
SNOWFALL ASSOCIATED WITH THE TRACKING SURFACE LOW. 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 ALSO EXPERIENCE A VARIETY OF MIXED PRECIPITATION TYPES INSTEAD
OF ALL SNOW. REGARDLESS OF PRECIPITATION TYPE, A SLIGHT RISK OF HEAVY SNOW IS
POSTED FOR MUCH OF THE TENNESSEE VALLEY AS WELL AS PORTIONS OF THE
MID-ATLANTIC, SOUTHEASTERN U.S., LOWER AND MIDDLE MISSISSIPPI VALLEY, AND
SOUTHERN PLAINS FOR JAN 9-10. GREATER SNOW ACCUMULATIONS ARE FAVORED FURTHER
NORTH WITH FAVORABLE LAKE-EFFECT SNOW CONDITIONS DOWNWIND OF LAKES ERIE AND
ONTARIO. THE GEFS PET INDICATES A 20% CHANCE OF 3-DAY ACCUMULATED SNOW WATER
EQUIVALENT (SWE) EXCEEDING THE 85TH PERCENTILE, AND MODEL ENSEMBLE TOTALS FOR
SNOWFALL FROM THE ECMWF CONTINUE TO DEPICT ENHANCED SNOWFALL NEAR THE GREAT
LAKES AND OVER THE APPALACHIANS FROM JAN 9-13, AFTER WHICH SNOWFALL TOTALS
TAPER OFF BELOW HAZARDOUS THRESHOLDS. THE MODERATE RISKS OF HEAVY SNOW POSTED
YESTERDAY HAVE BEEN REMOVED DUE TO A COMBINATION OF SOME OF THE ANTICIPATED
HEAVY SNOW SHIFTING INTO THE WEEK-1 PERIOD, AS WELL AS LOWER SNOWFALL TOTALS
INDICATED BY ECMWF ENSEMBLES RELATIVE TO PREVIOUS DAYS. A SLIGHT RISK OF HEAVY
SNOW HAS BEEN POSTED FOR PORTIONS OF THE CENTRAL AND NORTHERN PLAINS FOR JAN
9-13, WITH PASSING SHORTWAVE TROUGHS WITHIN NORTHWEST FLOW ALOFT FAVORED TO
PRODUCE SEVERAL ROUNDS OF SNOWFALL. WHILE LARGE ACCUMULATIONS ARE NOT
ANTICIPATED, WHEN COMBINED WITH THE RISK OF HIGH WINDS HIGHLIGHTED ABOVE THE
POTENTIAL FOR BLIZZARD CONDITIONS WARRANTS INCLUDING THIS HAZARD IN TODAY’S
OUTLOOK.
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 9-13 FOR THE AREAS HIGHLIGHTED ABOVE.
FORECASTER: DANNY BARANDIARAN
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