380
FXUS02 KWBC 230743
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
343 AM EDT THU OCT 23 2025
VALID 12Z SUN OCT 26 2025 - 12Z THU OCT 30 2025
***HEAVY RAIN FOR THE GULF COAST SUNDAY AND SNOW INCREASES FOR THE
ROCKIES THROUGH EARLY NEXT WEEK***
..GENERAL OVERVIEW
A SPLIT UPPER LEVEL FLOW PATTERN WILL BE IN PLACE ACROSS THE
CONTINENTAL U.S. FOR THIS WEEKEND, WITH A SOUTHERN STREAM
SHORTWAVE CROSSING THE SOUTH-CENTRAL U.S., WITH HEAVY RAIN AND
SOME STRONG THUNDERSTORMS FROM MISSISSIPPI TO GEORGIA. MEANWHILE,
AN AMPLIFYING UPPER TROUGH OVER THE WESTERN U.S. THIS WEEKEND WILL
HERALD A PATTERN CHANGE TO THE REGION, WITH COLDER CONDITIONS AND
WIDESPREAD SNOW FOR THE HIGHER TERRAIN THROUGH MONDAY, AND PERIODS
OF LIGHT TO MODERATE RAIN FOR THE PACIFIC NORTHWEST COAST. THIS
WESTERN U.S. TROUGH WILL LIKELY SPUR SURFACE CYCLOGENESIS OVER THE
NORTHERN PLAINS THAT WILL RESULT IN ANOTHER ROUND OF SHOWERS AND
STORMS EARLY NEXT WEEK ACROSS THE UPPER MIDWEST. A SEPARATE LOW
PRESSURE SYSTEM IS LIKELY TO DEVELOP NEAR THE EAST COAST TOWARDS
THE MIDDLE OF THE WEEK ALONG A FRONTAL BOUNDARY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z MODEL GUIDANCE SUITE IS IN GOOD OVERALL AGREEMENT ACROSS
THE CONTINENTAL U.S. FOR THE WEEKEND, WITH MAINLY MINOR MESOSCALE
DIFFERENCES, SO A MULTI-DETERMINISTIC MODEL BLEND WAS USED THROUGH
THIS TIME PERIOD. THE 00Z CMC STARTS BECOMING NOTICEABLY MORE
AMPLIFIED WITH A SECOND UPPER TROUGH ACROSS THE NORTHERN ROCKIES BY
MONDAY MORNING, AND THEN EXTREMELY AMPLIFIED WITH THAT TROUGH
GOING INTO TUESDAY TO THE POINT OF BECOMING AN OUTLIER SOLUTION
FROM THAT TIME FORWARD, AS IT DEVELOPS AN INTENSE UPPER LOW OVER
THE CENTRAL PLAINS THAT IS NOT SUPPORTED BY ENSEMBLE OR AIFS
GUIDANCE, SO NO 00Z CMC IS RECOMMENDED BEYOND MONDAY. IT IS ALSO ON
THE NORTHWESTERN SIDE OF THE MODEL TRACK WITH THE FUTURE TRACK OF
WHAT IS CURRENTLY TROPICAL STORM MELISSA. HOWEVER, THE PREVIOUS 12Z
RUN WAS MUCH BETTER ALIGNED WITH THE OTHER GUIDANCE IN COMPARISON
ACROSS THE CONTINENTAL U.S. OUTSIDE OF THE TROPICS. IT IS ALSO
WORTH NOTING THAT THE NBM IS LIKELY TOO LIGHT WITH RAINFALL ACROSS
THE SOUTHEAST U.S. FOR EARLY NEXT WEEK, SO THE WPC QPF WAS HIGHER
GIVEN A HEAVIER TREND IN THE DETERMINISTIC GUIDANCE. BY THE END
OF THE FORECAST PERIOD, THE GFS AND ECMWF HAVE TRENDED STRONGER
WITH A POTENTIAL COASTAL LOW DEVELOPING OFF THE EAST COAST, WITH
THE GFS FARTHER NORTH AND SLOWER TO DEVELOP IT. THE ENSEMBLE MEANS
WERE INCREASED TO ABOUT HALF BY NEXT THURSDAY AMID THE INCREASED
UNCERTAINTY IN MODEL SPECIFICS.
..WEATHER/HAZARDS HIGHLIGHTS
IT REMAINS THE CASE THAT HEAVY RAINFALL CAN BE EXPECTED ACROSS
PORTIONS OF THE CENTRAL GULF COAST REGION GOING INTO SUNDAY AS THE
SOUTHERN STREAM SHORTWAVE TRACKS EAST ACROSS THE REGION. THERE IS A
GOOD MODEL SIGNAL FOR 1 TO 3 INCH QPF FROM SOUTHERN MISSISSIPPI TO
THE FLORIDA PANHANDLE, AND THEREFORE THE INHERITED MARGINAL RISK
AREA HAS BEEN MAINTAINED FOR THE DAY 4/SUNDAY TIME PERIOD WITH A
MODEST EXPANSION TO THE EAST TO INCLUDE WESTERN GEORGIA. FOR THE
DAY 5/MONDAY TIME PERIOD, THE SIGNAL FOR HEAVIER RAINFALL HAS
INCREASED FOR THE COASTAL CAROLINAS AS A POTENTIAL LOW DEVELOPS
JUST OFFSHORE, AND A MARGINAL RISK AREA HAS BEEN INTRODUCED FROM
NEAR CHARLESTON, SC TO THE SOUTHERN OUTER BANKS OF NC. THERE IS A
GOOD CHANCE THAT RAINFALL AMOUNTS COULD TREND UPWARD IN LATER
FORECASTS, SO THIS REGION WILL CONTINUE TO BE MONITORED.
ANOTHER THING THAT WILL MAKE WEATHER HEADLINES IS THE INCREASE OF
HEAVY MOUNTAIN SNOW FROM THE CASCADES TO THE NORTHERN ROCKIES,
WHERE 1 TO LOCALLY 2 FEET OF SNOW IS BECOMING MORE LIKELY FOR THE
HIGHER RANGES SUNDAY AND INTO MONDAY AFTERNOON. THE INTENSITY OF
THE SNOW SHOULD TAPER OFF TOWARDS MONDAY NIGHT AND BEYOND AS
FORCING FOR ASCENT WEAKENS. A NEW SURFACE LOW IS LIKELY TO DEVELOP
BY MONDAY ACROSS THE NORTHERN PLAINS AS A POTENT SHORTWAVE EJECTS
EASTWARD FROM THE ROCKIES, SUPPORTING AN INCREASE IN SHOWERS/STORMS
AND GUSTY WINDS FROM THE DAKOTAS TO MINNESOTA.
THE PATTERN CHANGE COMING OUT WEST WILL RESULT IN COLDER WEATHER
FROM NORTHERN CALIFORNIA AND OREGON EASTWARD TO THE GREAT BASIN AND
NORTHERN ROCKIES THROUGH MONDAY. HIGHS ARE EXPECTED TO BE 5 TO 15
DEGREES BELOW AVERAGE, PERHAPS LOCALLY MORE, BUT OVERNIGHT LOWS
SHOULD BE CLOSER TO AVERAGE OWING TO INCREASED CLOUD COVER AND
PRECIPITATION. LATE SEASON WARMTH SHOULD BE THE CASE FROM THE
DAKOTAS TO THE MIDWEST THROUGH MONDAY BEFORE THESE AREAS ALSO GET A
COOL DOWN TOWARDS NEXT WEDNESDAY AS COLDER HIGH PRESSURE BUILDS IN
BEHIND THE COLD FRONT. MUCH OF THE EAST COAST REGION SHOULD
GENERALLY BE SLIGHTLY BELOW AVERAGE THROUGH MOST OF THE FORECAST
PERIOD.
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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