488
FXUS02 KWBC 231918
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
218 PM EST SUN NOV 23 2025
VALID 12Z WED NOV 26 2025 - 12Z SUN NOV 30 2025
..GENERAL OVERVIEW
A STRONG LOW PRESSURE SYSTEM CROSSING THE NORTHERN GREAT LAKES
MID-WEEK IS EXPECTED TO MOVE OVER QUEBEC, WITH A TRAILING COLD
FRONT THAT SHOULD EXIT THE EAST COAST BY THANKSGIVING MORNING. A
PLEASANTLY MILD AIRMASS AHEAD OF THE BOUNDARY WILL BE REPLACED BY
MUCH COLDER CONDITIONS BY THE END OF THE WEEK, WITH A SPRAWLING
CANADIAN SURFACE HIGH ENVELOPING AREAS FROM THE NORTHERN PLAINS TO
THE SOUTHEAST STATES. LAKE EFFECT SNOWS ARE FORECAST FROM MICHIGAN
TO NEW YORK STATE THROUGH THE END OF THE WORK WEEK, AND LOCALLY
HEAVY SNOW TOTALS WILL BE POSSIBLE. AN UPPER LEVEL TROUGH WILL
AMPLIFY OVER THE WESTERN U.S. NEXT WEEKEND, WHICH WILL LIKELY SPUR
SURFACE CYCLOGENESIS ACROSS THE WESTERN HIGH PLAINS WHILE A MORE
ZONAL FLOW PATTERN DEVELOPS OVER THE EASTERN HALF OF THE NATION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
OVERALL, THERE IS PRETTY GOOD MODEL AGREEMENT ON THE LARGE SCALE
PATTERN, BUT THERE IS STILL SIGNIFICANT UNCERTAINTY SURROUNDING THE
EVOLUTION OF UPPER LEVEL TROUGHING THAT WILL DEVELOP OVER THE WEST
LATE THIS WEEK. THIS UNCERTAINTY STEMS FROM LARGE UPSTREAM
DIFFERENCES OVER THE NORTH PACIFIC, WHICH ARE ALSO MAKING THE
MODELS STRUGGLE TO RESOLVE INDIVIDUAL SURFACE LOW PRESSURE SYSTEMS
THAT WILL IMPACT THE WEST THROUGHOUT THE WEEK. THE GFS/GEFS SEEMED
TO BE AN OUTLIER WITH THIS CYCLE, TRENDING FASTER AND LESS
AMPLIFIED WITH THE UPPER TROUGH THAN THE ECMWF/ECENS AND CMC/CMCE.
AT THE BEGINNING OF THE PERIOD, AGREEMENT WAS GOOD ENOUGH THAT A
GENERAL MODEL BLEND OF THE LATEST GFS/ECMWF/CMC PROVIDED A GOOD
STARTING POINT FOR THE FORECAST. BY THURSDAY, THE GFS BEGAN TO
DIVERGE IN THE WEST, AND THE BLEND LEANED MORE TOWARDS AN ECMWF/CMC
SOLUTION. FOR FRIDAY THROUGH SUNDAY, AN ECMWF/CMC SOLUTION WAS
STILL FAVORED AND ENSEMBLE MEANS FROM THE ECENS/CMCE WERE ADDED IN
INCREASING AMOUNTS TO SMOOTH OUT MODEL DIFFERENCES. THIS
MAINTAINED GOOD CONTINUITY WITH THE PREVIOUS FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
IN TERMS OF THE EXCESSIVE RAINFALL OUTLOOKS (EROS), THE DAY
4/WEDNESDAY ERO MAINTAINS THE MARGINAL RISK AREA ACROSS PORTIONS OF
NORTHWESTERN OREGON AND WESTERN WASHINGTON WHERE AN ATMOSPHERIC
RIVER ADVECTS COPIOUS MOISTURE TOWARDS THE TERRAIN, WITH SOME 2 TO
3 INCH RAINFALL TOTALS LIKELY. THERE WILL PROBABLY BE ABATEMENT IN
THE RAINFALL INTENSITY GOING INTO DAY 5/THANKSGIVING DAY, AND NO
RISK AREAS ARE CURRENTLY WARRANTED NATIONWIDE.
MEANWHILE, SNOW CHANCES WILL INCREASE FOR THE NORTH-CENTRAL U.S.
AND GREAT LAKES REGION WEDNESDAY THROUGH FRIDAY. MOISTURE MOVING
INLAND FROM THE NORTHWEST TO THE NORTHERN PLAINS WILL FALL AS
WINTRY PRECIPITATION, WITH SNOW CHANCES FROM THE NORTHERN PLAINS
TO THE UPPER MIDWEST AND HEAVY SNOW LIKELY IN THE NORTHERN
ROCKIES. HEAVY SNOW WILL ALSO BE POSSIBLE DOWNWIND OF THE GREAT
LAKES AS A BITTERLY COLD AIR MASS MOVES OVER THE RELATIVELY WARMER
LAKES ON THE BACKSIDE OF THE STRONG LOW PRESSURE SYSTEM MOVING INTO
CANADA. THE HIGHEST SNOW TOTALS WILL LIKELY BE IN THE MICHIGAN
UPPER PENINSULA WHERE 6-12+ INCHES WILL BE POSSIBLE.
LOOKING AHEAD TO SATURDAY, DEPENDING ON THE LEVEL OF MOISTURE
RETURN AHEAD OF THE DEVELOPING STORM SYSTEM OVER THE PLAINS,
SHOWERS AND THUNDERSTORMS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY FROM THE TEXAS/LOUISIANA GULF COAST TO THE MID/LOWER
MISSISSIPPI VALLEY. MODELS ARE SHOWING A CONSISTENT SIGNAL FOR
HEAVY RAIN IN THIS REGION, WHICH WILL CONTINUE TO BE MONITORED FOR
FLASH FLOOD POTENTIAL. ADDITIONALLY, MOISTURE OVER-RUNNING THE
ARCTIC AIRMASS OVER THE NORTHERN PLAINS COULD LEAD TO MORE
WIDESPREAD SNOWFALL CHANCES FROM WYOMING AND COLORADO TO THE UPPER
MIDWEST AND GREAT LAKES ON SATURDAY AND SUNDAY. HEAVY SNOW WILL BE
LIKELY FOR THE HIGHER TERRAIN OF THE CENTRAL ROCKIES.
IN TERMS OF TEMPERATURES, A MILD DAY FOR THIS TIME OF YEAR CAN BE
EXPECTED ON WEDNESDAY FROM FLORIDA TO THE NORTHEAST U.S. WITH HIGHS
RUNNING ABOUT 10-15 DEGREES ABOVE AVERAGE, BUT THIS WILL BE SHORT-
LIVED AS A STRONG COLD FRONT HERALDS THE ARRIVAL OF A DECEMBER-
LIKE AIRMASS TO THE REGION, DROPPING TEMPERATURES ABOUT 20 DEGREES
FOR MANY AREAS BY FRIDAY. A MUCH COLDER ARCTIC AIRMASS THEN OOZES
SOUTHWARD ACROSS MONTANA AND MUCH OF THE DAKOTAS BY NEXT WEEKEND,
WITH SOME SUBZERO OVERNIGHT LOWS WITHIN THE REALM OF POSSIBILITY
NEAR THE CANADIAN BORDER, WHILST TEMPERATURES REMAIN WARM ACROSS
SOUTHERN TEXAS.
DOLAN/HAMRICK
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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