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FXUS21 KWNC 132029
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST NOVEMBER 13 2024
SYNOPSIS: MULTIPLE MODEL ENSEMBLES DEPICT STRONG MID-LEVEL LOW PRESSURE OVER
THE CENTRAL CONTIGUOUS U.S. (CONUS) AT THE OUTSET OF WEEK-2, WHICH HAS THE
POTENTIAL TO BRING HEAVY RAIN, SNOW AND STRONG WINDS TO PORTIONS OF THE CENTRAL
AND EASTERN CONUS AS WELL AS A SHOT OF COLD AIR TO PORTIONS OF THE CENTRAL AND
SOUTHERN CONUS. PARTS OF THE SOUTHERN PLAINS COULD EXPERIENCE THE FIRST FREEZE
OF THE SEASON. STRONG SURFACE HIGH PRESSURE OVER THE GREAT BASIN FAVORS THE
DEVELOPMENT OF SANTA ANA WINDS FOR SOUTHERN CALIFORNIA. A POTENTIAL TROPICAL
CYCLONE (TC) IS FAVORED TO TRACK OVER THE SOUTHEAST GULF OF MEXICO LATE IN
WEEK-1 AND INTO WEEK-2 INCREASING CHANCES FOR HEAVY PRECIPITATION AND HIGH
WINDS ACROSS THE FLORIDA PENINSULA.
HAZARDS
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR PORTIONS OF THE SOUTHERN
PLAINS AND LOWER MISSISSIPPI VALLEY, THU-FRI, NOV 21-22.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR MUCH OF THE SOUTHERN PLAINS
AND LOWER MISSISSIPPI VALLEY, THU-SAT, NOV 21-23.
MODERATE RISK OF HEAVY SNOW FOR PORTIONS OF THE GREAT LAKES PRONE TO
LAKE-EFFECT SNOW, THU-SAT, NOV 21-23.
SLIGHT RISK OF HEAVY SNOW FOR MUCH OF THE GREAT LAKES, AS WELL AS PORTIONS OF
THE OHIO VALLEY, CENTRAL APPALACHIANS, AND NORTHEAST U.S., THU-SUN, NOV 21-24.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE NORTHEAST, THU-SAT, NOV
21-23.
MODERATE RISK OF HIGH WINDS FOR MUCH OF THE GREAT LAKES, OHIO AND TENNESSEE
VALLEYS, AS WELL AS PORTIONS OF THE MIDDLE AND UPPER MISSISSIPPI VALLEY,
CENTRAL APPALACHIANS, AND NORTHEAST U.S., THU-FRI, NOV 21-22.
SLIGHT RISK OF HIGH WINDS FOR MUCH OF THE EASTERN CONUS, THU-SAT, 21-23.
SLIGHT RISK OF HIGH WINDS FOR COASTAL PORTIONS OF SOUTHERN CALIFORNIA, THU, NOV
21.
SLIGHT RISK OF HIGH WINDS FOR THE FLORIDA PENINSULA, THU, NOV 21.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE FLORIDA PENINSULA, THU, NOV 21.
DETAILED SUMMARY
FOR SATURDAY NOVEMBER 16 - WEDNESDAY NOVEMBER 20:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY NOVEMBER 21 - WEDNESDAY NOVEMBER 27: ENSEMBLE SOLUTIONS FROM THE
GEFS AND ECENS BOTH DEPICT A FAIRLY AMPLIFIED HIGH FREQUENCY WAVETRAIN
EXTENDING FROM THE BERING SEA ACROSS THE NORTH PACIFIC AND NORTH AMERICA AND
INTO THE NORTH ATLANTIC, WITH ONE OF THE TROUGHS MOVING OVER THE CENTRAL CONUS
AT THE OUTSET OF WEEK-2. GIVEN THE HIGH WAVE NUMBER, THIS FEATURE IS FAVORED TO
MOVE EASTWARD QUICKLY AND DEAMPLIFY, SETTLING OVER THE GREAT LAKES AS THE JET
STREAM REORGANIZES INTO A LOWER FREQUENCY STATE. WHILE THE GEFS AND ECENS
DIFFER WITH REGARD TO THE LOCATION OF THE TROUGH AT THE BEGINNING OF THE
FORECAST PERIOD, THEY BOTH INDICATE A SIMILAR POTENTIAL FOR IMPACTFUL WEATHER
AS A RESULT OF THIS STORM SYSTEM.
SEVERAL RECENT DETERMINISTIC GFS RUNS DEPICT A SURFACE LOW FORMING IN THE LEE
OF THE ROCKIES LATE IN WEEK-1, GENERATING PERIODS OF POTENTIALLY HEAVY SNOW AND
STRONG WINDS ACROSS THE CENTRAL ROCKIES AND INTO THE CENTRAL AND NORTHERN
PLAINS BEFORE THE DEEP LOW PRESSURE CENTER MOVES EASTWARD INTO THE GREAT LAKES
REGION BY WEEK-2. ENSEMBLE AND DETERMINISTIC MODEL SOLUTIONS ARE CONVERGING
TOWARDS AN OCCLUDED LOW PRESSURE SYSTEM OVER ONTARIO, RESULTING IN A PROLONGED
PERIOD OF WESTERLY TO NORTHWESTERLY SURFACE FLOW OVER THE GREAT LAKES, WHICH
ARE AT OR NEAR RECORD HIGH SURFACE TEMPERATURES. COLD AIR ALOFT RESULTS IN VERY
STEEP LAPSE RATES, FURTHER CONTRIBUTING TO FAVORABLE LAKE-EFFECT SNOW
CONDITIONS. CONSENSUS AMONG MODELS IS FOR THIS FAVORABLE SETUP TO BE AT ITS
STRONGEST FOR NOV 21-23, THEREFORE A MODERATE RISK FOR HEAVY SNOW IS POSTED FOR
PORTIONS OF THE GREAT LAKES MOST PRONE TO LAKE-EFFECT SNOW, WHILE A BROADER
SLIGHT RISK OF HEAVY SNOW IS POSTED FOR THE GREAT LAKES, MUCH OF THE OHIO
VALLEY, AND PORTIONS OF THE CENTRAL APPALACHIANS AND NORTHEAST U.S. FOR NOV
21-24. FINALLY, FURTHER AHEAD OF THE LOW PRESSURE MODELS DEPICT ENHANCED
PRECIPITATION OVER PORTIONS OF THE NORTHEAST U.S., WITH ECMWF RAW PROBABILISTIC
GUIDANCE INDICATING AT LEAST A 20% CHANCE OF 3-DAY PRECIPITATION ACCUMULATIONS
EXCEEDING 1 INCH NORTH AND EAST OF NEW YORK CITY, THEREFORE A SLIGHT RISK OF
HEAVY PRECIPITATION IS POSTED FOR PORTIONS OF THE NORTHEAST U.S. FOR NOV. 21-23.
THE GFS DETERMINISTIC RUNS DESCRIBED ABOVE ALSO DEPICT STRONG SURFACE PRESSURE
GRADIENTS OVER MUCH OF THE EASTERN CONUS OVER THE FIRST HALF OF THE FORECAST
PERIOD. THIS IS LESS WELL-SUPPORTED BY THE PROBABILISTIC EXTREMES TOOLS (PETS)
FOR THE ECMWF AND GEFS, WHICH BOTH HAVE A WEAK SIGNAL FOR HIGH WINDS RELATIVE
TO SOLUTIONS EARLIER IN THE WEEK BUT GIVEN CONTINUED SUPPORT FROM DETERMINISTIC
AND ENSEMBLE RUNS, A SLIGHT RISK (20-40 PERCENT CHANCE) FOR HIGH WINDS REMAINS
FOR MUCH OF THE EASTERN CONUS FOR NOV 21-23. FURTHERMORE, A MODERATE RISK
(40-60 PERCENT CHANCE) FOR HIGH WINDS IS POSTED FOR MUCH OF THE GREAT LAKES,
OHIO AND TENNESSEE VALLEYS, AS WELL AS PORTIONS OF THE MIDDLE AND UPPER
MISSISSIPPI VALLEY, CENTRAL APPALACHIANS, AND NORTHEAST U.S., FOR NOV 21-22,
WHERE MODEL GUIDANCE HAS CONSISTENTLY PLACED VERY TIGHT SURFACE PRESSURE
GRADIENTS.
ANOMALOUSLY COLD AIR IS FAVORED TO BE ASSOCIATED WITH THE UPPER LEVEL TROUGH
OVER THE CENTRAL CONUS, BRINGING POTENTIALLY IMPACTFUL MINIMUM TEMPERATURES TO
PORTIONS OF THE SOUTHERN PLAINS. THE GEFS AND ECENS PETS BOTH INDICATE AT LEAST
20% PROBABILITIES OF MINIMUM TEMPERATURES FALLING BELOW THE 15TH PERCENTILE
OVER MUCH OF THE SOUTHERN PLAINS, AND AT LEAST 40% PROBABILITY OF SUB-FREEZING
TEMPERATURES FOR NORTH TEXAS, OKLAHOMA, AND ARKANSAS, WARRANTING A MODERATE
RISK FOR MUCH BELOW-NORMAL TEMPERATURES FOR THE AREA DESCRIBED TO COVER NOV
21-22. ADDITIONALLY, BOTH PETS INDICATE THE POTENTIAL FOR FROST CONDITIONS ALL
THE WAY TO THE U.S.-MEXICO BORDER AND EASTWARDS TOWARDS THE MISSISSIPPI RIVER,
THEREFORE A SLIGHT RISK FOR MUCH BELOW-NORMAL TEMPERATURES IS POSTED FOR THE
REMAINDER OF THE SOUTHERN PLAINS AND PORTIONS OF THE LOWER MISSISSIPPI VALLEY
FOR NOV 21-23.
A SURFACE HIGH PRESSURE SYSTEM OVER THE GREAT BASIN ASSOCIATED WITH THE SURGE
OF COLD AIR OVER THE GREAT PLAINS IS ANTICIPATED TO SET UP A STRONG PRESSURE
GRADIENT FAVORABLE FOR SANTA ANA WINDS LATE IN WEEK-1 AND INTO THE EARLY
PORTION OF WEEK-2. THERE ARE ACTIVE WILDFIRES IN THE AREA, SO A WIND EVENT SUCH
AS THIS MAY EXACERBATE ALREADY CHALLENGING CONDITIONS ON THE GROUND. A SLIGHT
RISK FOR HIGH WINDS IS POSTED FOR COASTAL SOUTHERN CALIFORNIA SOUTH OF SANTA
BARBARA FOR NOV 21, AFTER WHICH MODELS INDICATE A REDUCTION IN THE SURFACE
PRESSURE GRADIENT.
THE NATIONAL HURRICANE CENTER (NHC) IS CURRENTLY MONITORING THE WESTERN
CARIBBEAN FOR THE POTENTIAL OF TROPICAL CYCLONE (TC) FORMATION DURING THE NEXT
7 DAYS. REGARDLESS OF ANY POTENTIAL TC GENESIS OR SUBSEQUENT STORM FORMATION,
ENHANCED ATMOSPHERIC WATER CONTENT IS FORECAST TO BE WIDESPREAD OVER THE
CARIBBEAN AND SOUTHEASTERN GULF OF MEXICO. THE GEFS AND ECMWF PETS BOTH
INDICATE AT LEAST A 20% PROBABILITY OF 3-DAY PRECIPITATION TOTALS EXCEEDING THE
85TH PERCENTILE FOR PORTIONS OF THE SOUTHEAST U.S., WITH THE BEST AGREEMENT
OVER THE FLORIDA PENINSULA, WARRANTING A SLIGHT RISK FOR HEAVY PRECIPITATION
FOR NOV 21. A CO-LOCATED SLIGHT RISK OF HIGH WINDS IS ALSO POSTED FOR NOV 21,
CONSISTENT WITH MODEL SOLUTIONS TRENDING TOWARDS AN INTACT TC TRACKING ACROSS
FLORIDA.
FORECASTER: DANNY BARANDIARAN
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