013
FXUS21 KWNC 142021
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST NOVEMBER 14 2023
SYNOPSIS: INITIALLY STRONG MID-LEVEL LOW PRESSURE OVER THE CENTRAL CONTIGUOUS
U.S. (CONUS) WEAKENS QUICKLY AND MOVES EASTWARD DURING THE FORECAST PERIOD.
LINGERING AVAILABLE MOISTURE FROM ONSHORE FLOW INTO THE PACIFIC NORTHWEST
DURING WEEK-1 COUPLED WITH COLDER AIR MOVING IN FROM CANADA BRINGS A CHANCE FOR
HEAVY SNOW FOR THE NORTHERN ROCKIES AND HIGH PLAINS. SURFACE LOW PRESSURE IS
FORECAST TO MOVE THROUGH THE EASTERN CONUS EARLY IN WEEK-2, WITH ELEVATED
POTENTIAL FOR LINGERING EPISODES OF HIGH WINDS BEHIND THIS SYSTEM STRETCHING
FROM THE UPPER MIDWEST AND NORTHEAST, POSSIBLY PERSISTING INTO THE THANKSGIVING
HOLIDAY.
HAZARDS
SLIGHT RISK FOR HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHERN AND CENTRAL
APPALACHIANS, TENNESSEE AND OHIO VALLEYS, MID-ATLANTIC, AND NORTHEAST U.S.,
WED, NOV 22.
SLIGHT RISK FOR HIGH WINDS FOR PORTIONS OF THE GREAT LAKES, OHIO VALLEY,
CENTRAL APPALACHIANS, MID-ATLANTIC, AND NORTHEAST U.S., WED-THU, NOV 22-23.
SLIGHT RISK FOR HEAVY SNOW FOR PORTIONS OF THE NORTHERN ROCKIES AND NORTHERN
PLAINS, WED-THU, NOV 22-23.
DETAILED SUMMARY
FOR FRIDAY NOVEMBER 17 - TUESDAY NOVEMBER 21:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY NOVEMBER 22 - TUESDAY NOVEMBER 28: SURFACE LOW PRESSURE FORECAST
OFF THE COAST OF BRITISH COLUMBIA AT THE END OF WEEK-1 FAVORS ENHANCED ONSHORE
FLOW INTO THE NORTHWESTERN CONUS. WHILE THIS WILL BRING A ROUND OF WIND AND
RAIN TO THE WEST COAST, HAZARD THRESHOLDS ARE NOT ANTICIPATED TO BE EXCEEDED.
HOWEVER, A SLIGHT RISKS FOR HEAVY SNOW IS POSTED ACROSS THE NORTHERN ROCKIES
AND PORTIONS OF THE NORTHERN PLAINS FOR NOV 22-23 WHERE THE GEFS SNOW WATER
EQUIVALENT (SWE) PET INDICATES AT LEAST A 20 PERCENT CHANCE OF SWE EXCEEDING
THE 85TH CLIMATOLOGICAL PERCENTILE AND A HALF-INCH OVER SOME AREAS, AND THE
UNCALIBRATED ECMWF DEPICTS AT LEAST A 20 PERCENT CHANCE OF SNOWFALL EXCEEDING
4-INCHES.
THE 0Z ECMWF, GEFS, AND CANADIAN ENSEMBLES INDICATE THE POTENTIAL FOR SURFACE
LOW PRESSURE TO MOVE THROUGH THE EASTERN CONUS EARLY IN THE PERIOD, IN THE DAYS
LEADING UP TO THANKSGIVING. BOTH THE ECMWF AND GEFS PETS DEPICT 3-DAY
PRECIPITATION TOTALS HAVING AT LEAST A 20 PERCENT CHANCE OF EXCEEDING THE 85TH
CLIMATOLOGICAL PERCENTILE AND 1-INCH ACROSS PARTS OF THE EAST. THERE IS SOME
DISAGREEMENT AMONG MODELS WITH REGARD TO LOCATION AND SEVERITY OF POTENTIAL
PRECIPITATION, BUT THERE IS ENOUGH CONSENSUS TO KEEP A SLIGHT RISK OF HEAVY
PRECIPITATION HIGHLIGHTED ACROSS MUCH OF THE EASTERN THIRD OF THE CONUS FROM
THE TENNESSEE VALLEY AND CAROLINAS NORTHWARD THROUGH THE NORTHEAST FOR NOV 22.
DEPENDING ON THE STRENGTH OF THE SYSTEM, EPISODES OF HIGH WINDS ARE POSSIBLE
FROM THE UPPER MIDWEST TO THE NORTHEAST IN ITS WAKE, WITH THE ECMWF PET
INDICATING AT LEAST A 20 PERCENT CHANCE WIND SPEEDS EXCEED THE 85TH PERCENTILE
AND 20-MPH. THEREFORE, A SLIGHT RISK OF HIGH WINDS IS POSTED ACROSS THESE AREAS
FROM NOV 22-23, WHICH INCLUDES THE THANKSGIVING HOLIDAY.
STRONG RIDGING OVER ALASKA FAVORS ANOMALOUSLY WARM TEMPERATURES ACROSS MUCH OF
THE MAINLAND AND ALEUTIANS, WITH THE CONSOLIDATED GEFS AND ECMWF REFORECAST
TOOL DEPICTING THE HIGHEST MEAN WEEK-2 TEMPERATURE DEPARTURES ACROSS THE NORTH
SLOPE (AT LEAST 12 DEG F). RECENT MODEL RUNS INDICATE THE POSSIBILITY OF
TEMPERATURES ABOVE FREEZING FOR SOUTHWESTERN ALASKA, BRINGING THE POSSIBILITY
OF PREMATURE RIVER THAWING AND ASSOCIATED ICE JAMMING AND FLOODING. NO HAZARD
IS POSTED FOR NOW, BUT THE SITUATION WILL CONTINUE TO BE CLOSELY MONITORED.
FORECASTER: DANNY BARANDIARAN
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