501
FXUS02 KWBC 040703
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
203 AM EST THU DEC 4 2025
VALID 12Z SUN DEC 07 2025 - 12Z THU DEC 11 2025
...MODERATE TO STRONG MULTI-DAY AR POSSIBLE FOR THE PACIFIC
NORTHWEST NEXT WEEK...
..OVERVIEW
A CENTRAL TO EASTERN U.S. MEAN UPPER TROUGH AND BROAD CYCLONIC
FLOW WITH REINFORCING SHORTWAVES WILL CONTINUE TO DOMINATE DURING
MUCH OF THE MEDIUM RANGE PERIOD ACROSS THE CONUS. THIS WILL FAVOR
BELOW TO WELL BELOW NORMAL TEMPERATURES FOR THE PLAINS TO THE EAST
COAST INTO AT LEAST EARLY NEXT WEEK. NEAR TO ABOVE NORMAL
TEMPERATURES ARE FAVORED FOR THE WESTERN STATES UNDER THE INFLUENCE
OF UPPER RIDGING. A LINGERING FRONTAL BOUNDARY OVER THE SOUTHEAST
WILL LIKELY PROMOTE AN AREA OF LOCALLY HEAVIER RAIN THIS WEEKEND
WHILE A COUPLE OF CLIPPER SYSTEMS WILL IMPACT THE NORTHERN TIER
STATES AS WELL WITH WITH MODEST SNOW CHANCES. A COUPLE OF
ATMOSPHERIC RIVERS INTO THE REGION WILL BRING HEAVIER COASTAL RAINS
AND TERRAIN ENHANCED SNOWS FROM THE PACIFIC NORTHWEST THROUGH THE
NORTHERN ROCKIES NEXT WEEK ALONG WITH A THREAT OF HIGH WINDS TO
MONITOR.
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT SYNOPTICALLY THROUGH THE
MEDIUM RANGE PERIOD BUT THERE REMAINS QUITE A BIT OF UNCERTAINTY
IN THE DETAILS AND THE TIMING OF MULTIPLE SHORTWAVES THROUGH THE
NORTHERN TIER IMPACTING SENSIBLE WEATHER GRIDS. A SHORTWAVE
DROPPING INTO THE UPPER MIDWEST NEXT WEDNESDAY SHOWS SOME NOTABLE
AMPLITUDE DIFFERENCES WITH THE CMC MUCH FLATTER THAN THE ECMWF AND
GFS. THE GFS ALSO BECOMES FASTER THAN CONSENSUS WITH THIS AS IT
PUSHES THROUGH THE OHIO VALLEY INTO THE NORTHEAST BY THURSDAY. OUT
WEST, GUIDANCE SHOWS GOOD AGREEMENT ON A COUPLE OF SHORTWAVES
IMPACTING THE REGION EARLY TO MID NEXT WEEK. BY THURSDAY THOUGH,
THE GFS BRINGS ANOTHER SHORTWAVE INTO THE REGION WHILE THE CMC AND
ECMWF SUGGEST UPPER RIDGING, AND ARE CONSISTENT WITH THE ENSEMBLE
MEANS.
FOR THE WPC FORECAST, A GENERAL BLEND OF THE DETERMINISTIC MODEL
GUIDANCE WAS A GOOD STARTING POINT FOR THE FIRST HALF OF THE
PERIOD, WITH INCREASING WEIGHTING OF THE ENSEMBLE MEANS (WITH THE
ECMWF) ONWARD INTO DAYS 6 AND 7. GIVEN THE OVERALL AGREEMENT, THE
01 UTC NBM SEEMED TO PROVIDE A REASONABLY GOOD STARTING POINT FOR
MOST OF THE SENSIBLE WEATHER GRIDS, BUT DID HAVE TO SUPPLEMENT NBM
QPF TO INCREASE COVERAGE OF LIGHT PRECIPITATION WITH SYSTEMS MOVING
THROUGH THE NORTH- CENTRAL U.S./MIDWEST.
..WEATHER/HAZARDS HIGHLIGHTS
MODERATE TO HEAVY RAINFALL MAY CONTINUE INTO SUNDAY ACROSS
NORTHERN FLORIDA ALONG A LINGERING FRONTAL BOUNDARY. THIS FRONTAL
BOUNDARY MAY STALL FOR A PERIOD OF TIME, ALLOWING FOR SOME TRAINING
OF STORMS INTO THE SUNDAY AFTERNOON PERIOD, ALTHOUGH INSTABILITY
WILL BE LACKING SO NEXT EXPECTING A WIDESPREAD FLASH FLOOD THREAT.
A MARGINAL RISK WAS ADDED TO THE DAY 4/SUNDAY ERO TO ACCOUNT FOR AT
LEAST A LOCALIZED THREAT. RAIN SHOULD FINALLY CLEAR OUT OF THE
REGION BY NEXT MONDAY.
A SHORTWAVE LOOKS TO MOVE INTO THE PACIFIC NORTHWEST AROUND
SUNDAY, BRINGING SOME POTENTIAL FOR MODERATE RAIN AND MOUNTAIN
SNOWS. THE NEXT ONE BEGINNING MONDAY LOOKS QUITE A BIT STRONGER
WITH LATEST CW3E GUIDANCE SUGGESTING AT LEAST A MODERATE IF NOT
STRONG AR DUE TO BOTH HIGHER IVTS AND A LONGER DURATION EVENT. SOME
SIGNIFICANT MULTI-DAY TOTALS ARE POSSIBLE BOTH WITH COASTAL RAIN
AND HIGHER ELEVATION SNOWS ACROSS THE CASCADES. DID GO AHEAD WITH A
MARGINAL RISK FOR WESTERN WASHINGTON AND FAR NORTHWEST OREGON ON
THE DAY 5/MONDAY ERO, WITH LIKELY NEEDING ADDITIONAL RISK AREAS
BEYOND MONDAY ONCE IT GETS INTO THE ERO PERIOD. THERE IS ALSO A
RISK FOR TERRAIN ENHANCED WINDS INTO NEXT WEEK EXTENDING EASTWARD
INTO THE NORTH- CENTRAL STATES. ELSEWHERE, SEVERAL CLIPPER LIKE
SYSTEMS WILL ALSO BRING SOME RAIN AND SNOW TO PARTS OF THE MIDWEST,
GREAT LAKES/APPALACHIANS AND THE NORTHEAST NEXT WEEK.
TEMPERATURES ACROSS THE NORTH-CENTRAL U.S. TO THE EAST WILL REMAIN
BELOW NORMAL AT LEAST THROUGH THE WEEKEND, WITH SOME MODERATION
FROM WEST TO EAST EARLY NEXT WEEK. ON SUNDAY, DAYTIME HIGHS AND
MORNING LOWS COULD BE 20-25 DEGREES BELOW NORMAL PARTS OF THE
NORTHERN PLAINS/UPPER MIDWEST, WITH TEMPERATURES 10-20 DEGREES
BELOW NORMAL BY MONDAY INTO THE OHIO VALLEY AND NORTHEAST. AFTER
MONDAY, TEMPERATURES SHOULD MODERATE WITH ANOTHER SHOT OF COLD AIR
INTO THE NORTHERN TIER BY NEXT THURSDAY. THE WEST WILL TREND WARMER
INTO NEXT WEEK UNDERNEATH UPPER RIDGING, WITH WARMER THAN AVERAGE
TEMPERATURES ALSO SPREADING INTO THE CENTRAL AND SOUTHERN PLAINS BY
TUESDAY.
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 (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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