778
FXUS21 KWNC 261906
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 26 2024
SYNOPSIS: FOLLOWING ABOVE-NORMAL TEMPERATURES ACROSS THE EAST TO END 2024, A
PATTERN CHANGE IS FORECAST DURING EARLY JANUARY WITH A TRANSITION TO
BELOW-NORMAL TEMPERATURES. FORECAST CONFIDENCE IS LOWER TODAY DUE TO DIVERGING
MODEL SOLUTIONS. THE GFS ENSEMBLE MEAN (GEFS) FAVORS ARCTIC HIGH PRESSURE
SHIFTING SOUTH FROM CANADA WITH WIDESPREAD BELOW-NORMAL TEMPERATURES FROM THE
GREAT PLAINS TO THE EAST COAST AND ALSO AN INCREASED RISK OF A WINTER STORM
ACROSS THE EASTERN U.S. DURING EARLY TO MID-JANUARY. HOWEVER, THE ECMWF
ENSEMBLE MEAN (ECENS) WOULD FAVOR A MORE LIMITED COVERAGE OF BELOW-NORMAL
TEMPERATURES TO ONLY THE EAST AND AN INCREASED CHANCE OF HAZARDOUS WEATHER FOR
THE WEST COAST.
HAZARDS
SLIGHT RISK OF HEAVY HEAVY SNOW DOWNWIND OF LAKES ERIE AND ONTARIO, FRI, JAN 3.
SLIGHT RISK OF HIGH WINDS FOR THE NORTHEAST, FRI, JAN 3.
SLIGHT RISK OF HEAVY SNOW FOR THE NORTHERN AND CENTRAL ROCKIES ALONG WITH THE
NORTHERN AND CENTRAL GREAT PLAINS, FRI-MON, JAN 3-6.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR PORTIONS OF THE FLORIDA
PANHANDLE AND FLORIDA PENINSULA, SAT-MON, JAN 4-6.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR PARTS OF THE NORTH-CENTRAL
U.S., SUN-THU, JAN 5-9.
DETAILED SUMMARY
FOR SUNDAY DECEMBER 29 - THURSDAY JANUARY 02:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY JANUARY 03 - THURSDAY JANUARY 09: ON JANUARY 3RD, A STRONG LOW
PRESSURE SYSTEM IS FORECAST TO BE CENTERED OVER SOUTHEASTERN CANADA. A SLIGHT
RISK OF HIGH WINDS IS POSTED FOR THE NORTHEAST GIVEN THE PREDICTED STRENGTH OF
THE LOW PRESSURE SYSTEM AND A TIGHT PRESSURE GRADIENT. COLD AIR ADVECTION IS
EXPECTED TO PROMOTE LAKE-EFFECT SNOW JANUARY 3RD THUS A SLIGHT RISK OF HEAVY
SNOW IS DESIGNATED FOR AREAS DOWNWIND OF LAKES ERIE AND ONTARIO.
FROM JANUARY 4-6, THE GFS AND ECMWF ENSEMBLE MEANS DEPICT SURFACE HIGH PRESSURE
BECOMING CENTERED OVER THE SOUTHEAST WHICH COULD LEAD TO SUBFREEZING
TEMPERATURES FOR THE FLORIDA PANHANDLE AND PORTIONS OF THE FLORIDA PENINSULA,
INCLUDING THE CITRUS GROWING AREAS OF CENTRAL FLORIDA. A SLIGHT RISK OF MUCH
BELOW-NORMAL TEMPERATURES IS POSTED WHERE THE GEFS AND ECENS PROBABILISTIC
EXTREMES TOOLS (PETS) DEPICT MINIMUM TEMPERATURES HAVING MORE THAN A 20 PERCENT
CHANCE OF FALLING BELOW FREEZING. IF PROBABILITIES INCREASE TO 40 PERCENT FOR A
HARD FREEZE (MINIMUM TEMPERATURES AT OR BELOW 28 DEGREES F), THEN A MODERATE
RISK WILL LIKELY BE POSTED ON FRIDAY.
HIGH LATITUDE BLOCKING WITH A PREDICTED NEGATIVE ARCTIC OSCILLATION ALONG WITH
CROSS POLAR FLOW FAVOR A TRANSITION TO COLDER TEMPERATURES ACROSS THE EASTERN
U.S. DURING EARLY JANUARY. HOWEVER, THE GEFS AND ECENS DIVERGE ON WHERE AN
UPSTREAM 500-HPA RIDGE AXIS BECOMES ESTABLISHED EARLY IN WEEK-2. BY DAY 11
(JANUARY 6), THE GEFS DEPICTS A FULL-LATITUDE RIDGE EXTENDING FROM OFFSHORE OF
THE WEST COAST NORTH TO ALASKA WITH THE ECENS SHIFTING THAT RIDGE INLAND OVER
THE WEST. THIS DIFFERENT PLACEMENT IN THE 500-HPA RIDGE AXIS RESULTS IN LOW
FORECAST CONFIDENCE ON HOW EXPANSIVE THE ANOMALOUS COLD IS ACROSS THE CENTRAL
AND EASTERN U.S. THE GEFS SOLUTION WAS SLIGHTLY PREFERRED DUE TO ITS BETTER
CONSISTENCY WITH PRIOR MODEL RUNS. THEREFORE, A SLIGHT RISK OF MUCH
BELOW-NORMAL TEMPERATURES IS MAINTAINED TODAY FOR PORTIONS OF THE NORTH-CENTRAL
U.S. WHERE THERE IS A 20 PERCENT CHANCE OF MINIMUM TEMPERATURES FALLING BELOW
THE 15TH PERCENTILE AND CLOSE TO COLD ADVISORY LEVELS.
EARLY IN WEEK-2, THE GEFS AND CMCE DEPICT A SHORTWAVE TROUGH TRACKING EASTWARD
ACROSS THE NORTHERN TO CENTRAL ROCKIES WHICH COULD LEAD TO A PERIOD OF HEAVY
SNOW. THIS SHORTWAVE TROUGH MAY RESULT IN SURFACE LOW DEVELOPMENT ACROSS THE
NORTHERN OR CENTRAL GREAT PLAINS. BASED ON THESE MODEL SOLUTIONS ALONG WITH
SUPPORT FROM THE GEFS PET, A SLIGHT RISK OF HEAVY SNOW (JANUARY 3-6) IS
MAINTAINED FROM THE NORTHERN AND CENTRAL ROCKIES EAST TO THE NORTHERN AND
CENTRAL GREAT PLAINS.
THE ECENS WITH ITS SOLUTION OF A RIDGE AXIS INLAND AND A DEEP MID-LEVEL TROUGH
OVER THE NORTH PACIFIC WOULD SUPPORT AN INCREASED CHANCE OF HEAVY PRECIPITATION
AND HIGH-ELEVATION SNOW FOR THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA LATER
IN WEEK-2. SINCE THE GEFS FAVORS A RIDGE AXIS CLOSER TO THE WEST COAST AND A
MUCH DRIER WEEK-2 PERIOD, NO PRECIPITATION OR SNOW HAZARDS ARE POSTED FOR
NORTHERN CALIFORNIA AND THE PACIFIC NORTHWEST AT THIS TIME.
ENHANCED ONSHORE FLOW FAVORS ABOVE-NORMAL PRECIPITATION THROUGHOUT SOUTHERN
ALASKA. HOWEVER, DUE TO PRECIPITATION AMOUNTS NOT EXPECTED TO REACH HAZARDOUS
THRESHOLDS AND THE LATEST MODEL SOLUTIONS HAVING TRENDED SLIGHTLY DRIER, AN
ASSOCIATED HAZARD IS NOT DESIGNATED AT THIS TIME.
FORECASTER: BRAD PUGH
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