999
FXUS02 KWBC 310654
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
154 AM EST WED DEC 31 2025
VALID 12Z SAT JAN 3 2026 - 12Z WED JAN 7 2026
..GENERAL OVERVIEW
BROAD CYCLONIC FLOW ALOFT WILL BE IN PLACE ACROSS THE GREAT LAKES
REGION AND THE NORTHEAST GOING INTO THIS WEEKEND, AND THE TROUGH
BECOMES A LITTLE LESS AMPLIFIED AS THE DEEP LOW OVER CENTRAL CANADA
LIFTS OUT SOME TO THE NORTH. MEANWHILE, AN UPPER-LEVEL RIDGE WILL
INITIALLY BE IN PLACE ACROSS THE INTERMOUNTAIN WEST, AND THEN REACH
THE PLAINS OVER THE WEEKEND WITH WIDESPREAD ABOVE AVERAGE
TEMPERATURES. RAIN AND MOUNTAIN SNOW WILL BE COMMONPLACE ACROSS THE
WEST COAST STATES FRIDAY NIGHT AND GOING INTO THE WEEKEND AS
SHORTWAVES AND ONSHORE FLOW AFFECT THE REGION. ACROSS THE SOUTHERN
TIER STATES, A WAVE OF LOW PRESSURE DEVELOPS ALONG A FRONTAL
BOUNDARY AND BRINGS HIGHER RAINFALL CHANCES ACROSS THE SOUTHEAST
U.S. INTO SATURDAY. ANOTHER CLIPPER SYSTEM IS LIKELY TO CROSS THE
UPPER MIDWEST AND GREAT LAKES INTO EARLY NEXT WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE REMAINS IN GOOD SYNOPTIC SCALE AGREEMENT WITH THE
GENERAL PATTERN ACROSS THE CONTINENTAL U.S. GOING INTO THE WEEKEND
EAST OF THE ROCKIES, WITH A BROAD UPPER TROUGH OVER THE GREAT LAKES
AND NORTHEAST, AND A RIDGE AXIS SITUATED OVER THE WESTERN HIGH
PLAINS. THE LATEST GUIDANCE ALSO CONTINUES TO COME INTO BETTER
AGREEMENT REGARDING THE WAVE OF LOW PRESSURE THAT DEVELOPS ALONG A
FRONTAL BOUNDARY ACROSS THE SOUTHEAST STATES AND THEN EXITS THE
COAST OVER THE WEEKEND.
UNCERTAINTY INCREASES ACROSS THE WESTERN U.S. AS MULTIPLE SHORTWAVES
GRADUALLY FLATTEN THE UPPER LEVEL FLOW PATTERN ALONG THE WEST
COAST, AND DISPLACE THE RIDGE EASTWARD OVER THE PLAINS. THE CMC
BECAME FASTER THAN THE MODEL CONSENSUS BY SUNDAY WITH THE MAIN
TROUGH AXIS MOVING INLAND ACROSS THE WEST, SO MORE OF A GFS/ECMWF
APPROACH WAS USED FOR SUNDAY AND BEYOND. TOWARDS THE END OF THE
FORECAST PERIOD WEDNESDAY, THE AI GUIDANCE FAVORS A SOLUTION CLOSER
TO THE ECMWF ACROSS THE WESTERN U.S., SO THE FORECAST WAS HEDGED
MORE IN THE ECMWF/ECENS DIRECTION FOR THE TUESDAY-WEDNESDAY TIME
PERIOD FOR FRONTS AND PRESSURES. THE ENSEMBLE MEANS ACCOUNTED FOR
ABOUT HALF OF THE FORECAST BLEND BY THAT TIME.
..WEATHER/HAZARDS HIGHLIGHTS
A MORE ACTIVE WEATHER PATTERN DEVELOPS ALONG THE WEST COAST BY
IN TIME FOR THE WEEKEND AS A ORGANIZED LOW PRESSURE SYSTEM LIFTS
NORTHWARD WITH A COLD FRONT REACHING THE CALIFORNIA COAST. AN
ATMOSPHERIC RIVER WILL LIKELY AFFECT THE NORTHERN CALIFORNIA COAST
AND MOVE INLAND THROUGH SATURDAY AFTERNOON, BRINGING THE POTENTIAL
FOR 2 TO 4 INCHES OF RAINFALL FOR THE LOWER ELEVATIONS, WITH A
SECONDARY MAXIMA FOR THE EASTERN FOOTHILLS OF THE NORTHERN SIERRA
NEVADA. A MARGINAL RISK AREA WILL BE VALID HERE FOR BOTH SATURDAY
AND SUNDAY. HEAVY SNOW IS LIKELY FOR THE HIGHER TERRAIN.
ELSEWHERE ACROSS THE COUNTRY, AN AREA OF LOW PRESSURE IS EXPECTED
TO EXIT THE SOUTHEAST COAST ON SATURDAY. THIS QUICK-MOVING SYSTEM
WILL PRODUCE A CORRIDOR OF MODERATE RAINFALL AND SOME THUNDERSTORMS
FROM MISSISSIPPI EASTWARD TO THE COASTAL CAROLINAS, FOLLOWED BY
IMPROVING WEATHER ON SUNDAY. ANOTHER CLIPPER TYPE SYSTEM IS LIKELY
TO TRACK FROM THE UPPER MIDWEST, TO THE GREAT LAKES AND THEN NEW
ENGLAND SUNDAY INTO MONDAY. THIS RELATIVELY WEAK SYSTEM IS
EXPECTED TO PRODUCE A SWATH OF MAINLY LIGHT SNOW AND PERHAPS SOME
MIXED WINTRY PRECIPITATION ALONG THE SOUTHERN PORTION OF THE TRACK. IN
THE WAKE OF THE CLIPPER, SOME MINOR LAKE EFFECT AND UPSLOPE
SNOWFALL IS LIKELY DOWNWIND OF THE GREAT LAKES AND ACROSS PORTIONS
OF THE CENTRAL APPALACHIANS ON TUESDAY.
TEMPERATURES ARE LIKELY TO BE WARMER THAN AVERAGE ACROSS A WIDE
EXPANSE OF THE COUNTRY THIS WEEKEND INTO THE MIDDLE OF NEXT WEEK,
ESPECIALLY FROM THE ROCKIES TO THE CENTRAL AND SOUTHERN PLAINS.
HIGHS COULD BE 15 TO 25 DEGREES ABOVE AVERAGE FROM NORTHERN TEXAS
TO NEBRASKA, WITH LOWER 60S REACHING AS FAR NORTH AS NEBRASKA
SUNDAY INTO MONDAY. THE EXCEPTION TO THE MILD CONDITIONS WILL BE
FROM THE GREAT LAKES TO THE NORTHEAST AS THIS REGION REMAINS UNDER
THE GENERAL INFLUENCE OF AN UPPER TROUGH AND NORTH OF THE JET
STREAM, WHERE HIGHS SHOULD BE 5 TO 15 DEGREES BELOW AVERAGE, WITH
THE COLDEST READINGS ACROSS MAINE.
HAMRICK
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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