362
FXUS21 KWNC 151916
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST NOVEMBER 15 2023
SYNOPSIS: INITIALLY STRONG MID-LEVEL LOW PRESSURE OVER THE EASTERN CONTIGUOUS
U.S. (CONUS) WEAKENS QUICKLY AND MOVES EASTWARD DURING THE FORECAST PERIOD.
UPSLOPE FLOW PAIRED WITH REASONABLE ACCESS TO MOISTURE FROM LOWER LATITUDES AND
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 THROUGH THE NORTHEAST, PERSISTING THROUGH THE THANKSGIVING HOLIDAY.
HAZARDS
SLIGHT RISK FOR HIGH WINDS FOR PORTIONS OF THE GREAT LAKES, OHIO VALLEY,
CENTRAL APPALACHIANS, MID-ATLANTIC, AND NORTHEAST U.S., THU-FRI, NOV 23-24.
SLIGHT RISK FOR HEAVY SNOW FOR PORTIONS OF THE NORTHERN AND CENTRAL ROCKIES AND
ADJACENT HIGH PLAINS, THU-SAT, NOV 23-25.
DETAILED SUMMARY
FOR SATURDAY NOVEMBER 18 - WEDNESDAY NOVEMBER 22:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY NOVEMBER 23 - WEDNESDAY NOVEMBER 29: SURFACE LOW PRESSURE FORECAST
NEAR THE FOUR CORNERS REGION COUPLED WITH HIGH PRESSURE MOVING INTO THE GREAT
PLAINS SETS UP EASTERLY TO SOUTHEASTERLY FLOW ALONG THE EASTERN SLOPE OF THE
ROCKIES, WHICH IS FAVORABLE FOR ENHANCING POTENTIAL SNOWFALL. THIS, PAIRED WITH
COLDER AIR MOVING IN ALONG THE ROCKIES FAVORS POTENTIALLY HEAVY SNOW EARLY IN
THE FORECAST PERIOD. A SLIGHT RISK FOR HEAVY SNOW IS POSTED ACROSS THE NORTHERN
AND CENTRAL ROCKIES AND PORTIONS OF THE NORTHERN AND CENTRAL PLAINS FOR NOV
23-25 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. ANY POTENTIAL HAZARDS RELATED TO PRECIPITATION ARE
MOST LIKELY TO OCCUR DURING THE WEEK-1 PERIOD, BUT EPISODES OF HIGH WINDS ARE
POSSIBLE FROM THE UPPER MIDWEST TO THE NORTHEAST IN ITS WAKE. THE ECMWF PET
INDICATES AT LEAST A 20 PERCENT CHANCE WIND SPEEDS EXCEED THE 85TH PERCENTILE
AND 20-MPH, AND BOTH THE GEFS AND ECMWF RAW OUTPUT SHOW A FAIRLY TIGHT SURFACE
PRESSURE GRADIENT OVER THE NORTHEAST U.S. AT THE ONSET OF WEEK-2. THEREFORE, A
SLIGHT RISK OF HIGH WINDS IS POSTED ACROSS THESE AREAS FROM NOV 23-24, 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.
ADDITIONALLY, THE ABNORMALLY WARM TEMPERATURES BRING WITH THEM THE POSSIBILITY
OF A RAIN-ON-SNOW EVENT. NO HAZARD IS POSTED FOR NOW, BUT THE SITUATION WILL
CONTINUE TO BE CLOSELY MONITORED.
FORECASTER: DANNY BARANDIARAN
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