436
FXUS02 KWBC 101919
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
219 PM EST WED DEC 10 2025
VALID 12Z SAT DEC 13 2025 - 12Z WED DEC 17 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/TROUGH
EAST OF THE ROCKIES EARLY ON WILL KEEP THE NORTHERN TIER OF THE
COUNTRY IN AN ACTIVE PATTERN. AN ARCTIC AIRMASS WILL LIE ACROSS
PORTIONS OF THE NORTH- CENTRAL U.S. BRINGING MUCH BELOW NORMAL
TEMPERATURES AND POTENTIALLY HAZARDOUS COLD. BROAD RIDGING WILL
PERSIST ALONG THE WEST COAST/ROCKIES THROUGH THIS WEEKEND
CONTINUING THEIR ANOMALOUS WARMTH. EARLY TO MID NEXT WEEK, THE FLOW
PATTERN BECOMES QUASI-ZONAL WHICH SHOULD LEAD TO RENEWED HEAVY
RAIN/SNOW IN THE PACIFIC NORTHWEST AND NORTHERN CONTINENTAL DIVIDE.
INITIALLY, 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, BUT THAT BECOMES A MEMORY BY MID NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST 00Z/06Z DETERMINISTIC AND ENSEMBLE GUIDANCE REMAIN IN
GOOD OVERALL AGREEMENT THROUGH THE MEDIUM RANGE PERIOD, INDICATING
A GENERAL PATTERN TREND IN THE UPPER-LEVELS TOWARDS MORE ZONAL
FLOW COMPARED TO EASTERN UPPER-TROUGHING/WESTERN UPPER-RIDGING
WHICH HAS REMAINED INGRAINED FOR AWHILE, AND WITH SYSTEM PASSAGES
REMAINING RATHER PROGRESSIVE. AN INITIAL SYSTEM PASSING THROUGH AND
THEN DEPARTING THE EAST COAST THIS WEEKEND WILL BE FOLLOWED BY
ANOTHER SYSTEM MOVING INTO THE CENTRAL U.S. MID-NEXT WEEK, WHICH
IS TRENDING WETTER IN MOST GUIDANCE. THE PACIFIC NORTHWEST WILL
ALSO REMAIN IN AN ACTIVE ATMOSPHERIC RIVER PATTERN WITH ALL
GUIDANCE INDICATING A SERIES OF UPPER-LEVEL SHORTWAVES/PACIFIC
FRONTAL SYSTEMS IMPACTING THE REGION. THE UPDATED WPC FORECAST USED
A BLEND OF THE DETERMINISTIC 00Z ECMWF/CMC AND 06Z GFS FOR THE
FIRST PART OF THE PERIOD, WITH A HIGHER PERCENTAGE GIVEN TO THE
ECMWF/CMC DUE TO MORE FAVORABLE OVERLAP OF SYSTEM PROGRESSION,
PARTICULARLY FOR AN AREA OF LOW PRESSURE DEPARTING THE EAST COAST.
A CONTRIBUTION FROM THE 00Z ECENS MEAN WAS ADDED FOR THE MID- TO
LATTER PART OF THE PERIOD AS SMALLER-SCALE DIFFERENCES GROW, AND
THIS MEAN FELL BEST WITHIN THE ENVELOPE OF THE OTHER DETERMINISTIC
GUIDANCE. THE CONTRIBUTION FROM THE 00Z CMC WAS REDUCED IN TANDEM
AS TIMING WITH RESPECT TO THE CENTRAL U.S. SYSTEM BEGAN TO DIVERGE
FROM THE OTHER GUIDANCE LATE IN THE PERIOD, FAVORING A FASTER
PROGRESSION. THIS BLEND AND RESULTANT 500 MB AND FRONTAL PROGS
REMAINED GENERALLY CONSISTENT WITH THE PRIOR FORECAST.
MODIFICATIONS WERE MADE TO THE QPF FORECAST FROM THE 13Z NBM TO
INCREASE AMOUNTS FOR FAVORABLE LAKE- EFFECT ZONES DOWNWIND OF THE
GREAT LAKES. IN ADDITION, QPF WAS ADDED FROM A BLEND OF THE
GFS/ECMWF AND ECENS ACROSS PORTIONS OF THE SOUTH- CENTRAL U.S. TO
MIDWEST MID- NEXT WEEK AHEAD OF THE NOTED NEXT FRONTAL SYSTEM WHERE
THE NBM INDICATED LITTLE TO NO PRECIPITATION.
..WEATHER/HAZARDS HIGHLIGHTS
WHILE SOME PRECIPITATION CONTINUES FOR THE NORTHWEST/NORTHERN
ROCKIES EARLY ON, IT INCREASES IN COVERAGE EARLY TO MID NEXT WEEK
AS THE GENERAL FLOW PATTERN ATTEMPTS TO BECOME MORE ZONAL. MORE HEAVY
RAIN IS LOOKING LIKELY FOR COASTAL/LOWER ELEVATION LOCATIONS WITH
HEAVY SNOW FOR THE HIGHER TERRAIN OF THE WASHINGTON CASCADES AND
INCREASINGLY POSSIBLE ACROSS THE NORTHERN CONTINENTAL DIVIDE.
SHORTWAVES 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,
POTENTIALLY HEAVY EARLY NEXT WEEK NEAR THE WESTERN GULF COAST.
MOIST GULF RETURN FLOW AHEAD OF ANOTHER INCOMING FRONTAL SYSTEM
FROM THE MIDWEST TO SOUTH-CENTRAL U.S. LOOKS TO BRING BROADER RAIN
CHANCES MID-NEXT WEEK, THOUGH ANY REGIONS OF POTENTIALLY HEAVY
RAIN REMAIN MORE UNCERTAIN.
DAILY TEMPERATURES AS MUCH AS 15F TO 25F ABOVE SEASONAL AVERAGE
WILL SPREAD FROM THE WEST INTO THE THE ADJACENT HIGH PLAINS/PLAINS
EARLY TO MID NEXT WEEK. IN CONTRAST, 20F TO 30F BELOW AVERAGE
TEMPERATURES REMAIN FORECAST SATURDAY 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. MUCH OF THE
SOUTH, GULF COAST, AND FLORIDA WILL BE NEAR NORMAL THROUGH THE
PERIOD, WITH THE EAST COAST AND GREAT LAKES JOINING IN ON THE
RELATIVE THAW BY NEXT WEDNESDAY.
PUTNAM/ROTH
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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