198
FXUS02 KWBC 011847
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
147 PM EST SUN DEC 1 2024
VALID 12Z WED DEC 04 2024 - 12Z SUN DEC 08 2024
...ANOTHER BLAST OF ARCTIC COLD IN THE CENTRAL AND EASTERN U.S.
LATER THIS WEEK...
..HEAVY LAKE EFFECT SNOW TO CONTINUE THROUGH WEDNESDAY
..OVERVIEW
MEAN UPPER LEVEL TROUGHING OVER THE CENTRAL AND EASTERN U.S. WILL
DOMINATE THE WEATHER PATTERN THROUGH THIS WEEK INTO NEXT WEEKEND,
AND WEATHER SYSTEMS WILL BE DRIVEN BY SHORTWAVE TROUGHS ROTATING
AROUND THE BROAD UPPER LEVEL TROUGH. A COUPLE COLD FRONTS WILL PUSH
SOUTH ACROSS THE EASTERN TWO-THIRDS OF THE NATION THIS WEEK AND
WILL BRING ANOTHER BLAST OF COLD ARCTIC AIR. THIS PATTERN WILL ALSO
FAVOR LAKE EFFECT SNOW IN THE GREAT LAKES, BUT THE HEAVIEST SHOULD
COME TO AN END MID TO LATER THIS WEEK. ELSEWHERE, HIGH PRESSURE
WILL PERSIST IN THE WEST BEFORE A FRONTAL SYSTEM APPROACHES NEXT
WEEKEND, AND MOIST RETURN FLOW FROM THE GULF WILL SUPPORT DAILY
RAIN CHANCES ALONG THE GULF COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS SHOW FAIRLY GOOD AGREEMENT THROUGH MUCH OF THE PERIOD ON
THE OVERALL LARGE SCALE FLOW. CONFIDENCE HAS INCREASED IN A BIT
FASTER PROGRESSION OF THE COLD FRONT THROUGH THE EAST LATE THIS
WEEK, USHERING IN ANOTHER ROUND OF ARCTIC AIR FOR PARTS OF THE
NORTHERN PLAINS, MIDWEST, AND INTO THE EAST. THE NEXT SHORTWAVE
INTO THE NORTH-CENTRAL U.S. ON FRIDAY SHOULD BE WEAKER BUT DOES
SHOW SOME UNCERTAINTY IN TERMS OF TIMING. THE CMC WAS NOTABLY
FASTER WITH THIS AND WAS NOT USED IN THE BLEND BEYOND DAY 4. OUT
WEST, THE GUIDANCE SHOWS THE RIDGE SHIFTING EAST NEXT WEEKEND, BUT
SOME UNCERTAINTY IN THE TIMING OF A COLD FRONT INTO THE NORTHWEST.
THE WPC FORECAST BLEND WAS ANCHORED BY THE ECMWF THROUGH THE FIRST
HALF OF THE PERIOD, WITH SMALLER CONTRIBUTIONS FROM THE
GFS/UKMET/CMC. AFTER DAY 5, BEGAN INCREASING USAGE OF THE ENSEMBLE
MEANS THROUGH DAY 7 TO ACCOUNT FOR INCREASING UNCERTAINTY.
..WEATHER/HAZARDS HIGHLIGHTS
LAKE EFFECT SNOW IS FORECAST TO CONTINUE THIS WEEK AS A CLIPPER
LOW PRESSURE SYSTEM MOVES ACROSS THE REGION WEDNESDAY AND THURSDAY
FOLLOWED BY STRONG WEST-NORTHWESTERLY WINDS. SIGNIFICANT SNOW
ACCUMULATIONS WILL BE POSSIBLE IN FAVORED DOWNWIND LOCATIONS, AND
TRAVEL CONDITIONS WILL LIKELY BE HAZARDOUS, ESPECIALLY EARLIER IN
THE PERIOD. SNOW WILL ALSO BE POSSIBLE ELSEWHERE IN THE NORTHEAST
AS THE CLIPPER SYSTEM MOVES THROUGH, ESPECIALLY IN THE HIGHER
TERRAIN OF THE APPALACHIANS. CONDITIONS SHOULD IMPROVE BRIEFLY LATE
THIS WEEK, BUT ANOTHER LOW PRESSURE SYSTEM WILL BRING ANOTHER
CHANCE FOR WINTRY PRECIPITATION TO THE REGION NEXT WEEKEND.
THE REST OF THE NATION WILL BE MAINLY DRY THIS WEEK WITH A COUPLE
EXCEPTIONS. MOIST RETURN FLOW FROM THE GULF WILL RESULT IN DAILY
RAIN CHANCES ALONG THE GULF COAST AND INTO PORTIONS OF THE SOUTH.
THERE WILL LIKELY BE ENOUGH INSTABILITY TO SUPPORT LOCALLY HEAVY
RAINFALL ON WEDNESDAY IN PORTIONS OF SOUTHEAST TEXAS AND LOUISIANA,
AND THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR THESE
AREAS. THE RISK OF HEAVY RAINFALL WILL DECREASE THURSDAY THROUGH
THE END OF THE WEEK AS INSTABILITY DECREASES AND PRECIPITATION
BECOMES MORE SPREAD OUT ACROSS THE GULF COAST REGION AS FRONTS MOVE
THROUGH. PRECIPITATION CHANCES WILL ALSO RETURN TO THE NORTHWEST
LATE THIS WEEK INTO NEXT WEEKEND AS A PACIFIC FRONTAL SYSTEM
APPROACHES AND PUSHES INLAND.
TEMPERATURES WILL DROP BELOW NORMAL FOR PARTS OF THE NORTH-CENTRAL
TO EASTERN U.S. THIS WEEK AS A COLD FRONT USHERS IN ANOTHER BLAST
OF ARCTIC AIR. DAYTIME HIGHS FROM THE UPPER MIDWEST INTO THE EAST
COULD BE 10-20 DEGREES BELOW NORMAL. ELSEWHERE, TEMPERATURES WILL
BE MILD FOR THIS TIME OF YEAR, GENERALLY NEAR TO SLIGHTLY ABOVE
AVERAGE WITH THIS MILDER AIR GRADUALLY EXPANDING EAST WITH TIME.
SANTORELLI/DOLAN
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC MEDIUM
RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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