981
FXUS02 KWBC 090602
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
102 AM 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
A BROAD UPPER LEVEL TROUGH WITH REINFORCING SHORTWAVES WILL
CONTINUE TO DOMINATE AREAS EAST OF THE ROCKIES WITH BROAD RIDGING
PERSISTING 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 GUIDANCE SHOWS EXCELLENT AGREEMENT ON THE OVERALL LARGE SCALE
PATTERN, EVEN EXTENDING INTO A NUMBER OF SHORTWAVE DETAILS. FOR
THE FIRST HALF OF THE PERIOD, A GENERAL DETERMINISTIC MODEL BLEND
WORKED WELL AS A STARTING POINT FOR THE WPC 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 ACROSS THE NORTHWEST/NORTHERN ROCKIES SHOULD
CONTINUE EARLY ON. SNOW IS POSSIBLE IN THE HIGHEST TERRAIN OF THE
WASHINGTON CASCADES AND INCREASINGLY POSSIBLE ACROSS THE NORTHERN
CONTINENTAL DIVIDE AS THE FLOW PATTERN TRIES TO BECOME MORE ZONAL.
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.
A STRONG TEMPERATURE GRADIENT IS FORECAST ACROSS THE HIGH
PLAINS/PLAINS WITH 15-25F ABOVE AVERAGE TEMPERATURES ACROSS THE
WEST WHICH SPREAD INTO THE HIGH PLAINS WITH TIME EARLY NEXT WEEK
AND 20-30F BELOW AVERAGE TEMPERATURES FRIDAY INTO MONDAY FROM THE
NORTHERN PLAINS ACROSS THE GREAT LAKES, MIDWEST, AND OHIO VALLEY
WHILE 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.
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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