498
FXUS21 KWNC 252011
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST NOVEMBER 25 2024
SYNOPSIS: MULTIPLE MODELS CONTINUE TO SHOW SURFACE HIGH PRESSURE ADVANCING
SOUTHEASTWARD FROM THE CANADIAN PRAIRIES ACROSS MOST OF THE CENTRAL AND EASTERN
CONTIGUOUS U.S. (CONUS), WHICH INCREASES THE CHANCES FOR MUCH BELOW NORMAL
TEMPERATURES FOR PORTIONS OF THIS AREA. THE COLD AIR OVERRUNNING THE UNUSUALLY
WARM GREAT LAKES IS EXPECTED TO CONTRIBUTE TOWARDS THE GENERATION OF
LAKE-ENHANCED SNOW SHOWERS AND SQUALLS OVER THE CLIMATOLOGICALLY FAVORED AREAS
DOWNWIND OF THE LAKES. THERE ARE INCREASED CHANCES FOR FIRST FREEZES ACROSS THE
SOUTHERN TIER OF THE CONUS, WHICH MAY REACH AS FAR SOUTH AS THE ORLANDO AREA IN
CENTRAL FLORIDA. FOR MOST OF THE EASTERN CONUS, SIGNIFICANT UNCERTAINTY
CONTINUES AMONG THE MODEL GUIDANCE, ESPECIALLY WITH RESPECT TO THE LOCATION,
TIMING, AND TRACK OF INDIVIDUAL LOW PRESSURE SYSTEMS WITHIN THE WEEK-2 PERIOD.
THIS MAKES IT VERY DIFFICULT TO SPECIFY DETAILS OF WEATHER-RELATED HAZARDS.
HAZARDS
HIGH RISK OF MUCH BELOW NORMAL TEMPERATURES ACROSS MUCH OF ALABAMA AND GEORGIA,
EXTENDING INTO THE FLORIDA PANHANDLE, TUE, DEC 3.
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES ACROSS MOST OF THE SOUTHEAST,
TENNESSEE VALLEY, AND SOUTHERN MID-ATLANTIC REGION, TUE-WED, DEC 3-4.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FROM EASTERN PARTS OF THE LOWER
AND MIDDLE MISSISSIPPI VALLEY EASTWARD TO THE ATLANTIC COAST, FROM SOUTHERN NEW
ENGLAND TO CENTRAL FLORIDA, TUE-MON, DEC 3-9.
SLIGHT RISK OF PERIODS OF HEAVY LAKE-ENHANCED SNOWFALL ACROSS THE
CLIMATOLOGICALLY FAVORED SNOWBELT AREAS DOWNWIND OF THE GREAT LAKES, POSSIBLY
AS FAR SOUTH AS THE SMOKY MOUNTAINS IN EASTERN TENNESSEE, TUE-SAT, DEC 3-7.
SLIGHT RISK OF HIGH WINDS FROM ABOUT THE NORTHERN HALF OF THE MISSISSIPPI
VALLEY EASTWARD ACROSS THE GREAT LAKES AND OHIO VALLEY TO THE EAST COAST FROM
MAINE TO VIRGINIA, TUE-MON, DEC 3-9.
DETAILED SUMMARY
FOR THURSDAY NOVEMBER 28 - MONDAY DECEMBER 02:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY DECEMBER 03 - MONDAY DECEMBER 09: THE GEFS AND ECENS ENSEMBLE MEANS
INDICATE A BROAD TROUGH STRETCHING ACROSS THE EASTERN ONE-THIRD TO ONE-HALF OF
THE CONUS DURING WEEK-2. THERE CONTINUES TO BE SIGNIFICANT UNCERTAINTY AMONG
THE VARIOUS DETERMINISTIC AND ENSEMBLE MEAN MODELS REGARDING THE DEVELOPMENT
AND EXPECTED EVOLUTION OF LOW PRESSURE SYSTEMS AND RELATED IMPACTFUL WEATHER
ACROSS THE CENTRAL AND EASTERN CONUS.
SEVERAL HIGH PRESSURE CENTERS AND RELATED COLD AIR MASSES INITIALLY OVER
WEST-CENTRAL CANADA ARE PREDICTED TO ADVANCE SOUTHEASTWARD ACROSS MOST OF THE
CENTRAL AND EASTERN CONUS DURING WEEK-2. THERE IS A SLIGHT RISK (20-40% CHANCE)
OF MUCH BELOW NORMAL TEMPERATURES (15TH HISTORICAL PERCENTILE OR LOWER) POSTED
FROM EASTERN PARTS OF THE LOWER AND MIDDLE MISSISSIPPI VALLEY EASTWARD TO THE
ATLANTIC COAST, FROM SOUTHERN NEW ENGLAND TO CENTRAL FLORIDA, DEC 3-9. MINIMUM
OVERNIGHT TEMPERATURES ON DECEMBER 3RD MAY REACH 32 DEGREES F OR SLIGHTLY LOWER
AS FAR SOUTH AS ORLANDO, FL. ELEVATED PROBABILITIES FOR A HARD FREEZE (28 DEG F
OR COLDER) ARE DEPICTED IN THE GEFS AND ECENS PROBABILISTIC EXTREMES TOOLS
(PETS) AS FAR SOUTH AS THE FLORIDA PANHANDLE AND EXTREME NORTHERN PORTIONS OF
THE PENINSULA, SPARING ALL BUT PERHAPS THE NORTHERNMOST FRINGES OF THE FLORIDA
CITRUS BELT. A MODERATE RISK (40-60%) CHANCE OF MUCH BELOW NORMAL TEMPERATURES
IS POSTED FOR MUCH OF THE REGION DELINEATED BY THE SLIGHT RISK, AND IS VALID
DEC 3-4. A HIGH RISK (GREATER THAN 60% CHANCE) OF MUCH BELOW NORMAL
TEMPERATURES IS POSTED FOR MUCH OF ALABAMA, GEORGIA, AND THE FLORIDA PANHANDLE,
DEC 3. THIS REGION IS HIGHLY VULNERABLE TO ITS FIRST DAMAGING FREEZE OF THE
SEASON. WELL TO THE NORTH, ALONG THE NORTHERNMOST PORTIONS OF THE SLIGHT RISK
AREA OF MUCH BELOW NORMAL TEMPERATURES, THE PETS INDICATE MINIMUM TEMPERATURES
OF APPROXIMATELY +10 DEG F, AND WINDS OF AT LEAST 20 MPH. THE RESULTING WIND
CHILL VALUES ARE EXPECTED TO APPROACH THE NEW COLD CRITERIA FOR THIS AREA OF
ABOUT -5 DEG F.
COLD AIR STREAMING ACROSS THE UNUSUALLY WARM WATERS OF THE GREAT LAKES IS
LIKELY TO PROMOTE LAKE-ENHANCED SNOWFALL FOR THE CLIMATOLOGICAL DOWNWIND
SNOWBELT AREAS. PERIODS OF HEAVY SNOW (LOCALLY 6 INCHES OR MORE) WARRANT THE
POSTING OF A SLIGHT RISK FOR THESE AREAS, DEC 3-7. BLOWING AND DRIFTING SNOW
MAY DRASTICALLY REDUCE VISIBILITY WITHIN SNOWBANDS, POSING A SERIOUS DANGER TO
COMMUTERS. WITH THE PREDICTED DOMINANCE OF COLD, DRY AIR MASSES AND
NORTHWESTERLY FLOW EAST OF THE ROCKIES, THE BEST CHANCE FOR ANY RAIN IS NEAR
THE WESTERN GULF COAST DURING THE MIDDLE AND LATTER PORTIONS OF THE FORECAST
PERIOD. THE PETS ALSO SHOW PRECIPITATION NEAR THE NORTHEAST AND MID-ATLANTIC
COASTS DURING THE FORECAST PERIOD, BUT AMOUNTS ARE NOT EXPECTED TO REACH
HAZARDOUS CRITERIA AND THE EXACT PLACEMENT OF THE PRECIPITATION IS UNCERTAIN.
GIVEN THE LARGE UNCERTAINTY AMONG TODAY’S DETERMINISTIC AND ENSEMBLE MEAN
SOLUTIONS, NO HAZARDOUS (NON-SNOW) PRECIPITATION AREAS ARE DELINEATED DUE TO
REDUCED CONFIDENCE.
A SLIGHT RISK OF EPISODIC HIGH WINDS (AT LEAST 20-25 MPH) IS DEPICTED FROM
ABOUT THE NORTHERN HALF OF THE MISSISSIPPI VALLEY EASTWARD ACROSS THE GREAT
LAKES AND OHIO VALLEY TO THE EAST COAST FROM MAINE TO VIRGINIA, DEC 3-9. THIS
IS ASSOCIATED WITH THE EXPECTED PASSAGE OF SEVERAL LOW PRESSURE SYSTEMS DURING
THE PERIOD. THESE ARE MOST LIKELY TO BE CLIPPER-TYPE SYSTEMS THAT ORIGINATE
OVER THE CANADIAN PRAIRIES AND TRAVEL QUICKLY SOUTHEASTWARD, EMBEDDED DEEP
WITHIN COLD, DRY AIR MASSES. AS SUCH, THESE CLIPPER SYSTEMS OFTEN PRODUCE
FAIRLY LIGHT SNOWFALL ACCUMULATIONS, AS OPPOSED TO OTHER MID-LATITUDE SYSTEMS
THAT TEND TO TRAVEL ALONG THE SOUTHERN AND EASTERN BOUNDARIES OF ARCTIC AIR
MASSES AND HAVE ACCESS TO WARMER AND MORE MOIST AIR.
A SERIES OF SURFACE LOWS ARE PREDICTED TO FORM OVER THE GULF OF ALASKA, WHICH
MAY BRING UNSETTLED WEATHER TO SOUTH-CENTRAL AND SOUTHEASTERN PORTIONS OF THE
STATE. CONDITIONS ARE NOT ANTICIPATED TO SUPPORT WIDESPREAD HAZARDS AT THIS
TIME.
FORECASTER: ANTHONY ARTUSA
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