047
FXUS02 KWBC 092002
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
302 PM EST TUE DEC 9 2025
VALID 12Z FRI DEC 12 2025 - 12Z TUE DEC 16 2025
...POTENTIALLY HAZARDOUS COLD IS POSSIBLE FOR PORTIONS OF THE
NORTHERN PLAINS AND UPPER MIDWEST THIS WEEKEND...
..OVERVIEW
MULTIPLE SHORTWAVES TRAVERSING THROUGH A BROAD UPPER LOW WILL KEEP
THE NORTHERN TIER OF THE COUNTRY IN AN ACTIVE PATTERN. BROAD
RIDGING WILL PERSIST ALONG THE WEST COAST/ROCKIES THROUGH THIS
WEEKEND, THOUGH THE AMPLITUDE OF BOTH ARE FORECAST TO
WEAKEN/BROADEN WITH TIME. WHILE THE HEAVY PRECIPITATION AND HIGH
WIND THREAT FADES IN THE NORTHWEST, GENERALLY PROGRESSIVE CLIPPER
SYSTEMS WILL BE FAVORED IN THIS PATTERN EAST OF THE ROCKIES WITH
ENHANCED NORTHERN TIER WIND/SNOW CHANCES AND LAKE EFFECT SNOW IN
THE LEE OF THE GREAT LAKES. AN ARCTIC AIRMASS WILL MOVE IN TO
PORTIONS OF THE NORTH- CENTRAL U.S. BRINGING MUCH BELOW NORMAL
TEMPERATURES AND POTENTIALLY HAZARDOUS COLD.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST SUITE OF GUIDANCE MAINTAINS OVERALL ABOVE AVERAGE
CLUSTERING OF THE DOMINANT NORTHERN STREAM PATTERN. A GENERAL BLEND
OF THE GLOBALS ALONG WITH THE NBM WERE USED TO INITIALIZE THE
SURFACE FRONTS/PRESSURES/500 HPA HEIGHTS.
FOR SUNDAY INTO MONDAY,
THERE ARE ENOUGH DIFFERENCES TO INCORPORATE SOME OF THE 12Z
ECMWF/NAEFS MEANS. THE QPF STARTED WITH THE 01Z NBM BUT NEEDED
SIGNIFICANT INCREASES IN THE GREAT LAKES THROUGH THE PERIOD, THE
NORTHWEST MID TO LATE PERIOD, AND PORTIONS OF THE PLAINS AND OHIO
VALLEY LATE IN THE PERIOD, WHERE INCORPORATION OF THE 18Z AND 00Z
GFS/00Z ECMWF APPEARED NECESSARY, ESPECIALLY NEAR THE GULF COAST
WHERE THE NBM WAS INEXPLICABLY DRY, PARTICULARLY WHEN COMPARED TO
PAST COUPLE WET CANADIAN GLOBAL RUNS. POPS ADJUSTMENTS WERE MADE TO
ACCOUNT FOR THE QPF CHANGES. FOR THE REMAINDER OF THE GRIDS, THE
01Z NBM SEEMED LIKE A GOOD STARTING POINT.
..WEATHER/HAZARDS HIGHLIGHTS
PRECIPITATION SHOULD CONTINUE FOR THE NORTHWEST/NORTHERN ROCKIES
AND MAY INCREASE IN COVERAGE EARLY NEXT WEEK AS THE GENERAL FLOW
PATTERN ATTEMPTS TO BECOME MORE ZONAL. SNOW IS POSSIBLE IN THE
HIGHEST TERRAIN OF THE WASHINGTON CASCADES AND INCREASINGLY
POSSIBLE ACROSS THE NORTHERN CONTINENTAL DIVIDE.
A CLIPPER SYSTEM/DISTURBANCE INTO THE NORTHERN HIGH PLAINS WILL
INTERACT WITH A STATIONARY FRONTAL BOUNDARY AND THE NORTHERN
ROCKIES TO BRING HEAVY SNOW THREATS TO PORTIONS OF CENTRAL TO
EASTERN MONTANA FRIDAY, WITH SEVERAL INCHES OF SNOW POSSIBLE.
ADDITIONAL ENERGY ROUNDING THE BASE OF THE TROUGH CENTERED OVER THE
EASTERN THIRD OF THE COUNTRY WILL BRING ROUNDS OF GENERALLY LIGHT
TO MODERATE PRECIPITATION, MAINLY SNOW, INTO THE MIDWEST/GREAT
LAKES AND EASTWARD TOWARDS THE APPALACHIANS AND NORTHEAST THROUGH
THE WEEKEND. TO THE SOUTH, REINFORCING FRONTS SLOWING AS THEY
APPROACH FLORIDA/THE GULF COAST WILL BRING THE THREAT OF RAIN.
DAILY TEMPERATURES AS MUCH AS 15F TO 25F ABOVE SEASONAL AVERAGE
WILL SPREAD FROM THE WEST INTO THE THE ADJACENT HIGH PLAINS/PLAINS
BY EARLY NEXT WEEK. IN CONTRAST, 20F TO 30F BELOW AVERAGE
TEMPERATURES FRIDAY INTO MONDAY FROM THE NORTHERN PLAINS ACROSS THE
GREAT LAKES, MIDWEST, AND OHIO VALLEY WILL WEAKEN SOMEWHAT AS THE
AIRMASS MIGRATES INTO THE EAST NEXT TUESDAY. THIS MAY RESULT IN
HAZARDOUS COLD AS MORNING TEMPERATURES DIP BELOW ZERO WITH WIND
CHILLS NEAR -20 DEGREES. THIS AIRMASS WILL MODERATE SOMEWHAT AS IT
MOVES INTO THE OHIO VALLEY AND EAST NEXT WEEK. MUCH OF THE SOUTH,
GULF COAST, AND FLORIDA WILL BE NEAR NORMAL THROUGH THE PERIOD.
CAMPBELL/ROTH/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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