421
FXUS02 KWBC 251726
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1225 PM EST SAT NOV 25 2023
VALID 12Z TUE NOV 28 2023 - 12Z SAT DEC 02 2023
..OVERVIEW
AN UPPER LOW OVER/NEAR HUDSON BAY WILL ALLOW FOR GENERAL TROUGHING
WITH SOME EMBEDDED SHORTWAVES TUES-THURS ACROSS THE GREAT LAKES
AND NORTHEAST. THIS PATTERN WOULD SUPPORT A MULTI-DAY PERIOD OF
ENHANCED LAKE EFFECT SNOWS, ONGOING FROM THE END OF THE SHORT
RANGE PERIOD, LOCALLY HEAVY AT TIMES. AN INITIAL RIDGE OVER THE
WEST ON TUESDAY SHOULD BE REPLACED BY MEAN TROUGHING AS A CLOSED
LOW DROPS INTO THE SOUTHWEST WITH A REINFORCING AMPLIFIED
SHORTWAVE/ADDITIONAL EMBEDDED LOW FRIDAY-SATURDAY. THIS SHOULD
PROMOTE RIDGE BUILDING DOWNSTREAM ACROSS THE SOUTHEAST AND
EVENTUALLY THE EAST COAST BY NEXT WEEKEND. MUCH OF NEXT WEEK
SHOULD BE RELATIVELY QUIET AND DRY, WITH THE EXCEPTION OF THE
GREAT LAKES AND INCREASED MOISTURE AND PRECIPITATION MOVING INTO
THE SOUTH-CENTRAL U.S. BY LATE IN THE WEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE OPERATIONAL GUIDANCE IS IN REASONABLE AGREEMENT REGARDING THE
EVOLUTION OF THE SYNOPTIC PATTERN ACROSS THE LOWER 48 THROUGH DAY
5. THE ENSEMBLES CAPTURE THE DAYS 6 AND 7 PATTERN WELL. THE MAIN
AREA OF UNCERTAINTY IS THE DESCENDING TROUGH FROM BRITISH COLUMBIA
ON DAY 5. A GENERAL MODEL BLEND CONSISTING OF THE 00Z
ECMWF/CMC/UKMET AND 06Z GFS WAS USED FOR DAYS 3-5, THEN A MAJORITY
ENSEMBLE MEAN (00Z CMCE/ECE AND 06Z GEFS) BLEND WAS USED FOR DAYS
6 AND 7.
..WEATHER/HAZARDS HIGHLIGHTS
FAVORABLE WESTERLY COLD FLOW OVER THE STILL RELATIVELY WARM GREAT
LAKES WILL CONTINUE TO PROMOTE A MULTI-DAY PERIOD OF ACCUMULATING
LAKE EFFECT SNOW ESPECIALLY DOWNWIND OF LAKES ERIE AND ONTARIO,
WITH THE BEST CHANCE FOR POSSIBLY HEAVY TOTALS ON TUESDAY. MODELS
SHOW AGREEMENT ON A FAVORABLE LAKE EFFECT EVENT MONDAY INTO
TUESDAY (AND POSSIBLE ADDITIONAL BEYOND), BUT GIVEN THE SMALL
SCALE OF THE HEAVY SNOWBANDS, MINOR SHIFTS IN LOCATION OF THE
BANDS WOULD PROVIDE CONSIDERABLY DIFFERENT CONDITIONS AND
ACCUMULATIONS OVER SLIGHTLY DIFFERENT AREAS. ELSEWHERE ACROSS THE
COUNTRY, CONDITIONS LOOK MOSTLY DRY THROUGH NEXT WEEK THOUGH SOME
LIGHT PRECIPITATION MAY ACCOMPANY A SHORTWAVE INTO THE WEST AROUND
MIDWEEK. PRECIPITATION CHANCES ALONG THE GULF COAST REGION TO
PERHAPS AS FAR NORTH AS THE MIDDLE MISSISSIPPI VALLEY LOOK TO
INCREASE AGAIN BY LATE WEEK AS A WARM FRONT LIFTS NORTHWARD
THROUGH THE GULF OF MEXICO BRINGING POSSIBLY AT LEAST LOCALLY
HEAVY RAINFALL.
MUCH OF THE SOUTH-CENTRAL TO EASTERN U.S. SHOULD SEE NEAR TO BELOW
NORMAL TEMPERATURES THROUGH THE FIRST HALF OF NEXT WEEK WITH
DECENT COVERAGE OF HIGHS AND LOWS 10-15F BELOW CLIMATOLOGY. THE
WEST-CENTRAL U.S. SHOULD BE MODERATING BACK TOWARD NORMAL MID WEEK
WITH THE INTERIOR WEST COOLING BACK DOWN DURING THE LATTER HALF OF
THE WEEK DUE TO TROUGHING ALOFT. AN EXCEPTION TO THE BELOW AVERAGE
TEMPERATURES MAY BE ACROSS THE NORTHERN PLAINS, WHERE BY TUESDAY
AND BEYOND LOWS IN THE 20S AND HIGHS IN THE 40S ARE EXPECTED,
WHICH ARE AROUND 5-15F ABOVE NORMAL. ABOVE AVERAGE TEMPERATURES
SHOULD SPREAD INTO THE MISSISSIPPI VALLEY/MIDWEST AND THE GULF
COAST AROUND NEXT FRIDAY-SATURDAY AS UPPER RIDGING BUILDS OVER THE
REGION.
KEBEDE/SANTORELLI
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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES ARE AT:
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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