257
FXUS02 KWBC 010635
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
135 AM EST THU JAN 1 2026
VALID 12Z SUN JAN 4 2026 - 12Z THU JAN 8 2026
***HEAVY RAIN AND MOUNTAIN SNOW EXPECTED FOR CALIFORNIA***
..GENERAL OVERVIEW
BROAD CYCLONIC FLOW ALOFT WILL INITIALLY BE IN PLACE ACROSS THE
GREAT LAKES REGION AND THE NORTHEAST ON SUNDAY, FOLLOWED BY A
TRANSITION TO MORE ZONAL FLOW GOING INTO EARLY NEXT WEEK AS THE
TROUGH LIFTS OUT. THE UPPER LEVEL RIDGE THAT WILL INITIALLY BE IN
PLACE ACROSS THE INTERMOUNTAIN WEST WILL REACH THE PLAINS EARLY IN
THE FORECAST PERIOD WITH WIDESPREAD ABOVE AVERAGE TEMPERATURES.
RAIN AND MOUNTAIN SNOW WILL BE COMMONPLACE ACROSS THE WEST COAST
STATES SUNDAY INTO MONDAY AS SHORTWAVES AND ONSHORE FLOW AFFECT
THE REGION. A CLIPPER TYPE SYSTEM IS LIKELY FROM THE GREAT LAKES TO
THE NORTHEAST THROUGH MONDAY, AND A NEW STORM SYSTEM LIKELY
DEVELOPS OVER THE MID-SOUTH TOWARDS WEDNESDAY INTO THURSDAY.
..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 THAT LIFTS OUT AND BECOMES MORE ZONAL, AND A RIDGE
AXIS SITUATED OVER THE WESTERN HIGH PLAINS. THE CMC WAS A LITTLE
SLOWER WITH THE EXIT OF THE LOW PRESSURE OFF THE SOUTHEAST COAST
SUNDAY, SO A GFS/ECMWF BLEND IS BETTER FOR THAT REGION.
UNCERTAINTY INCREASES MORE 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
LATEST MODEL GUIDANCE HAS IMPROVED COMPARED TO EARLIER RUNS, AND THE
ENSEMBLE MEANS ACCOUNTED FOR ABOUT HALF OF THE FORECAST BLEND BY
NEXT THURSDAY.
..WEATHER/HAZARDS HIGHLIGHTS
A SERIES OF SHORTWAVE TROUGHS WILL AFFECT THE WEST COAST REGION
THROUGH SUNDAY AND GOING INTO EARLY NEXT WEEK, WITH A LIKELY
ATMOSPHERIC RIVER EVENT FOR INITIALLY NORTHERN CALIFORNIA THROUGH
SATURDAY NIGHT, AND THEN AFFECTING MORE OF THE STATE TO INCLUDE
SOUTHERN CALIFORNIA BY SUNDAY WHERE A GREATER INFLUX OF DEEP
PACIFIC MOISTURE IS ADVECTED TOWARDS THE TERRAIN. GIVEN THE
POTENTIAL FOR 2 TO LOCALLY 4 INCHES OF RAINFALL ACROSS PORTIONS OF
THE TRANSVERSE RANGE, IN COMBINATION WITH RECENT HEAVY RAINS, A
SLIGHT RISK AREA WILL BE VALID FOR THIS REGION ON THE NEW DAY
4/SUNDAY OUTLOOK, AND MARGINAL RISK AREAS EXTENDING FARTHER NORTH
TO INCLUDE MORE OF THE STATE. THERE IS LIKELY SOME ABATEMENT GOING
INTO DAY 5/MONDAY, BUT STILL ENOUGH QPF ACROSS THE WESTERN SLOPES
OF THE SIERRA NEVADA TO SUPPORT A MARGINAL RISK.
ELSEWHERE ACROSS THE COUNTRY, A 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, FOLLOWED BY WARMER
TEMPERATURES. TOWARDS THE END OF THE PERIOD, A NEW LOW PRESSURE
SYSTEM DEVELOPING OVER THE MID-SOUTH AND OHIO VALLEY SHOULD RESULT
IN INCREASING RAINFALL CHANCES WEDNESDAY NIGHT INTO THURSDAY WITH
PERHAPS A FEW THUNDERSTORMS IN THE WARM SECTOR OF THE LOW.
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 THE POTENTIAL FOR A FEW RECORD HIGHS TO BE SET.
THERE SHOULD ALSO BE SOME MODERATION FROM THE RECENT COLD WEATHER
FROM THE GREAT LAKES TO THE NORTHEAST AS THE UPPER TROUGH LIFTS OUT
AND WITH MORE WESTERLY FLOW FROM THE PACIFIC, WITH READINGS
INITIALLY A LITTLE BELOW AVERAGE AND THEN RETURNING TO NEAR NORMAL
LEVELS FOR EARLY JANUARY.
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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