979
FXUS02 KWBC 011925
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
225 PM EST MON DEC 1 2025
VALID 12Z THU DEC 04 2025 - 12Z MON DEC 08 2025
...RECORD COLD LIKELY FOR THE CORN BELT/MIDWEST/MID-ATLANTIC
THURS/FRI...
..OVERVIEW
NEGATIVE HEIGHT ANOMALIES WILL MEANDER ACROSS THE HIGH LATITUDES
(ALASKA AND CANADA) THROUGH THE PERIOD, WITH A WEAKENING POSITIVE
HEIGHT ANOMALY OVER THE NORTHEASTERN PACIFIC. THIS FAVORS BROAD
CYCLONIC FLOW ACROSS MUCH OF THE CONUS AND GENERALLY BELOW TO WELL
BELOW NORMAL TEMPERATURES FOR THE PLAINS EASTWARD TO THE EAST COAST
AND NORTH OF FLORIDA. RECORD COLD LOW TEMPERATURES (AND COLD HIGH
TEMPERATURES) ARE LIKELY THURSDAY AND FRIDAY FROM THE CORN BELT
EASTWARD TO PARTS OF THE MID-ATLANTIC. NEAR TO ABOVE NORMAL
TEMPERATURES ARE FAVORED FOR THE WESTERN STATES DOWNSTREAM OF THE
CORE OF THE UPPER RIDGE. WITH THE UPPER TROUGH TOUCHING THE GULF
COAST THURSDAY, A FRONTAL SYSTEM THERE WILL MOVE EASTWARD AND
PROMOTE AN AREA OF LOCALLY HEAVIER RAIN ALONG THE I-10 CORRIDOR.
TREND BY THE WEEKEND HAS BEEN FOR A FLATTER SYSTEM TO SCOOT OUT TO
SEA THEREAFTER, BUT SOME WINTRY PRECIPITATION IS POSSIBLE ON ITS
NORTHERN SIDE. A COUPLE OF CLIPPER SYSTEMS WILL IMPACT THE NORTHERN
TIER STATES AS WELL THROUGH THE PERIOD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THROUGH THE 00Z/06Z MODEL CYCLE, THERE WAS GOOD OVERALL/SYNOPTIC
AGREEMENT THROUGH THE PERIOD. THOUGH THE GFS/CANADIAN/ECMWF
DIFFERED IN SOME DETAILS (MOST NOTABLY AROUND SUNDAY IN THE
MIDWEST), A BLENDED/ENSEMBLE-FOCUSED STARTING POINT WAS SUFFICIENT
AS THE DETERMINISTIC RUNS WERE WITHIN THE EXPECTED ERROR BARS OF
THE FORECAST. THIS MEANT THAT THE 13Z NBM WAS ALSO A GOOD STARTING
POINT FOR THE SENSIBLE WEATHER GRIDS. PUT IN A LITTLE MORE WEIGHT
TOWARD THE ECMWF-LED CLUSTER (WITH ITS ENSEMBLE MEAN) FOR THE DAY
5-7 PERIOD, WITH SOME SUPPORT FROM THE AI/ML MODELS.
..WEATHER/HAZARDS HIGHLIGHTS
HEAVY RAIN WILL SPREAD OVER THE CENTRAL GULF COAST BY THURSDAY AND
EXPAND INTO THE SOUTHEAST FRIDAY INTO THE WEEKEND. THE WPC DAY
4/THURSDAY ERO CONTINUES TO SHOW A MARGINAL RISK FROM NEAR HOUSTON
AND ACROSS SOUTHERN LOUISIANA TO MOBILE. FOR FRIDAY/DAY 5, THE
MARGINAL RISK ENCOMPASSES PARTS OF THE SOUTHEAST ALONG THE FRONTAL
BOUNDARY WHICH MAY STALL FOR A PERIOD OF TIME ALLOWING FOR SOME
TRAINING OF STORMS. INSTABILITY MAY BE LACKING OVERALL WHICH SHOULD
LIMIT THE FLASH FLOOD THREAT TOWARD THE I-10 CORRIDOR.
THE SYSTEM IN THE SOUTHEAST EARLY THIS WEEKEND WILL LIFT OUT TO
SEA BY SUNDAY, BUT MAY STILL SPREAD SOME LIGHT PRECIPITATION
(RAIN/SNOW) ON ITS NORTHERN SIDE ACROSS THE MID-ATLANTIC AND
PERHAPS NEW ENGLAND. AHEAD OF THAT SYSTEM, LAKE EFFECT SNOW WILL
LINGER OVER THE GREAT LAKES ON THURSDAY THEN TAPER OFF ON FRIDAY AS
A FRONT CLEARS THE REGION. OVER THE PAC NW, SEVERAL PACIFIC
SYSTEMS WILL PUSH INTO WESTERN CANADA WITH TRAILING RAIN/SNOW OVER
WA/OR AND EASTWARD TO THE NORTHERN/CENTRAL ROCKIES THROUGH THE
PERIOD.
SURGES OF BELOW AVERAGE TEMPERATURES CONTINUE FOR THE CENTRAL AND
EASTERN U.S. INTO LATE WEEK AS THE SPRAWLING LOW OVER HUDSON BAY
PERSISTS. A SURGE FROM THE NORTHERN PLAINS THROUGH THE NORTHEAST
OCCURS INTO FRIDAY WITH LOW TEMPERATURES OF 5 TO 20 DEGREES BELOW
ZERO, WHICH WILL LIKELY SET DAILY RECORD LOWS. HIGH TEMPERATURES IN
THE TEENS AND LOW 20S ON THURSDAY WILL ALSO SET DAILY RECORD COLD
HIGH TEMPERATURES. WIND CHILLS OF -20 TO -30F ARE FORECAST FOR
PORTIONS OF THE NORTHERN PLAINS AND UPPER MIDWEST THURSDAY MORNING.
THE NEXT COLD SURGE MAY FOLLOW THE SAME PATH BUT PERHAPS BE OF
LESSER MAGNITUDE THIS WEEKEND. THE WEST WILL SEE ABOVE NORMAL
TEMPERATURES (ESPECIALLY THE GREAT BASIN) LATE WEEK THROUGH THIS
WEEKEND.
FRACASSO/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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