855
FXUS21 KWNC 122015
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST NOVEMBER 12 2024
SYNOPSIS: MODEL ENSEMBLES DEPICT A 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 SNOW AND STRONG WINDS TO PORTIONS OF THE CENTRAL CONUS
AS WELL AS A SHOT OF COLD AIR TO PORTIONS OF THE CENTRAL AND SOUTHERN CONUS,
POTENTIALLY BRINGING THE FIRST FREEZE OF THE SEASON TO PARTS OF THE SOUTHERN
PLAINS. STRONG SURFACE HIGH PRESSURE OVER THE GREAT BASIN FAVORS THE
DEVELOPMENT OF SANTA ANA WINDS FOR SOUTHERN CALIFORNIA. MOISTURE TRANSPORT FROM
THE TROPICS LEADS TO THE POTENTIAL FOR HEAVY PRECIPITATION FOR THE FLORIDA
PENINSULA.
HAZARDS
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR PORTIONS OF CENTRAL
OKLAHOMA, AND WESTERN, CENTRAL, AND NORTHERN TEXAS, WED-THU, NOV 20-21.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR MUCH OF THE SOUTHERN PLAINS,
WED-FRI, NOV 20-22.
SLIGHT RISK OF HEAVY SNOW FOR PORTIONS OF THE CENTRAL AND NORTHERN PLAINS AND
ALONG THE FRONT RANGE OF THE ROCKIES, WED-FRI, NOV 20-22.
MODERATE RISK FOR HIGH WINDS FOR PORTIONS OF THE CENTRAL AND NORTHERN PLAINS,
WED-FRI, NOV 20-22.
SLIGHT RISK OF HIGH WINDS FOR MUCH OF THE GREAT PLAINS, MIDDLE AND UPPER
MISSISSIPPI VALLEY, AND GREAT LAKES, WED-FRI, NOV 20-22.
SLIGHT RISK OF HIGH WINDS FOR COASTAL PORTIONS OF SOUTHERN CALIFORNIA, WED-THU,
NOV 20-21.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE FLORIDA PENINSULA, WED-FRI, NOV
20-22.
DETAILED SUMMARY
FOR FRIDAY NOVEMBER 15 - TUESDAY NOVEMBER 19:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY NOVEMBER 20 - TUESDAY NOVEMBER 26: 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 LOCATED 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
ACROSS THE CENTRAL ROCKIES AND INTO THE CENTRAL AND NORTHERN PLAINS AS THE LOW
PRESSURE CENTER MOVES EASTWARD DURING WEEK-2. ADDITIONALLY, THE UNCALIBRATED
ECENS INDICATES WIDESPREAD PROBABILITIES OF AT LEAST 20% FOR EXCEEDING 4 INCHES
OF SNOW ACCUMULATION OVER PORTIONS OF THE NORTHERN PLAINS, WITH THE POTENTIAL
FOR 6 INCHES OR GREATER FOR PORTIONS OF THE CENTRAL ROCKIES AND ADJACENT PLAINS
FOR NOV 20-22. THEREFORE A SLIGHT RISK FOR HEAVY SNOW IS POSTED FOR THE REGIONS
LISTED ABOVE FOR NOV 20-22.
THE GFS DETERMINISTIC RUNS DESCRIBED ABOVE ALSO DEPICT STRONG SURFACE PRESSURE
GRADIENTS OVER MUCH OF THE GREAT PLAINS AND INTO THE GREAT LAKES EARLY IN THE
FORECAST PERIOD. THIS IS LESS WELL-SUPPORTED BY THE PROBABILISTIC EXTREMES
TOOLS (PETS) FOR THE ECMWF AND GEFS, WHICH BOTH HAVE A WEAKER SIGNAL FOR STRONG
WIND OVER THE GREAT PLAINS RELATIVE TO YESTERDAY, BUT GIVEN CONTINUED SUPPORT
FROM DETERMINISTIC RUNS A SLIGHT RISK (20-40 PERCENT CHANCE) FOR HIGH WINDS
REMAINS FOR MUCH OF THE GREAT PLAINS, THE MIDDLE AND UPPER MISSISSIPPI VALLEY,
AND GREAT LAKES REGIONS FOR NOV 20-22. FURTHERMORE, A MODERATE RISK (40-60
PERCENT CHANCE) FOR HIGH WINDS IS POSTED FOR PORTIONS OF THE CENTRAL AND
NORTHERN PLAINS FOR NOV 20-22 WHERE MODEL GUIDANCE HAS CONSISTENTLY PLACED VERY
TIGHT SURFACE PRESSURE GRADIENTS. LATE IN WEEK-2 MODEL SOLUTIONS ARE HINTING AT
AN EASTWARD SHIFT IN THESE ENHANCED WINDS, SETTING UP FAVORABLE CONDITIONS FOR
LAKE-ENHANCED PRECIPITATION FOR THE GREAT LAKES REGION, A CONCERN GIVEN
NEAR-RECORD WARM WATER TEMPERATURES THERE. NO HAZARD IS POSTED AT THIS TIME BUT
THE SITUATION WILL BE CLOSELY MONITORED IN THE COMING DAYS.
ANOMALOUSLY COLD AIR IS FAVORED TO BE ASSOCIATED WITH THE UPPER LEVEL TROUGH
OVER THE WESTERN CONUS, BRINGING POTENTIALLY IMPACTFUL MINIMUM TEMPERATURES TO
PORTIONS OF THE CENTRAL CONUS. 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, WITH WIDESPREAD POTENTIAL FOR TEMPERATURES
BELOW FREEZING FOR NORTH TEXAS AND CENTRAL OKLAHOMA, WARRANTING A MODERATE RISK
FOR MUCH BELOW-NORMAL TEMPERATURES FOR THE AREA DESCRIBED TO COVER NOV 20-21.
ADDITIONALLY, BOTH PETS INDICATE THE POTENTIAL FOR FROST CONDITIONS ALL THE WAY
TO THE U.S.-MEXICO BORDER, THEREFORE A SLIGHT RISK FOR MUCH BELOW-NORMAL
TEMPERATURES IS POSTED FOR THE REMAINDER OF THE SOUTHERN PLAINS FOR NOV 20-22.
A SURFACE HIGH PRESSURE SYSTEM OVER THE GREAT BASIN ASSOCIATED WITH THE SURGE
OF COLD AIR OVER THE PLAINS ALSO SETS 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 20-22,
CONSISTENT WITH MODEL DEPICTIONS OF THE EVOLUTION OF PRESSURE GRADIENTS ALONG
THE COAST.
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 BEHAVIOR,
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 20-22.
FORECASTER: DANNY BARANDIARAN
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