625
FXUS02 KWBC 230753
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
253 AM EST TUE DEC 23 2025
VALID 12Z FRI DEC 26 2025 - 12Z TUE DEC 30 2025
..OVERVIEW
AN AMPLIFIED AND WARMING UPPER RIDGE WILL SHIFT THROUGH THE EAST-
CENTRAL U.S. LATE THIS WEEK, AS DEEP TROUGHING OFF THE WEST COAST
SHIFTS INLAND BY THE WEEKEND TO FINALLY BRING AN END TO THE
ATMOSPHERIC RIVER (AR) IMPACTING CALIFORNIA. HEAVY TO SIGNIFICANT
RAINFALL THOUGH WILL CONTINUE THROUGH AT LEAST THURSDAY/CHRISTMAS
DAY FOR SOUTHERN CALIFORNIA WITH RAINFALL COVERAGE AND INTENSITY
WEAKENING BY FRIDAY AND ESPECIALLY THE WEEKEND. WIDESPREAD, BUT
RELATIVELY MODEST ACTIVITY WILL ALSO CONTINUE IN THIS PERIOD FOR
THE INTERMOUNTAIN WEST AND ROCKIES. ACROSS THE MIDDLE PART OF THE
NATION, THE BIG STORY WILL BE UNSEASONABLE WARMTH AND POSSIBLE
RECORD WARM TEMPERATURES. THE COLDER NORTHERN TIER MAY SEE PLOWABLE
SNOW CHANCES FROM THE UPPER GREAT LAKES AND NOW MORE BROADLY ACROSS
THE NORTHEAST AND INTO THE NORTHERN MID-ATLANTIC AS SHORTWAVES AND
FRONTAL SYSTEMS PASS THROUGH. EXPECT ENHANCED LAKE EFFECT SNOWS
SUNDAY/MONDAY IN STRONG COLD FLOW IN THE WAKE OF MAIN LOW PASSAGE.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST MODEL OVERALL SHOWS GOOD AGREEMENT, NOW EXTENDING IN TIME
OUT THROUGH THE UPCOMING HOLIDAY WEEKEND IN A PATTERN WITH
SEEMINGLY ABOVE NORMAL PREDICTABILITY. A GFS/ECMWF/CANADIAN/UKMET
COMPOSITE SETS A GOOD FORECAST BASIS. UNCERTAINTY GROWS INTO EARLY
NEXT WEEK, ESPECIALLY AS IT PERTAINS TO THE EVOLUTION OF AN
EAST/NORTHEAST PACIFIC MEAN UPPER TROUGH POSITION AS ASSOCIATED
ENERGIES WORK INTO WESTERN NORTH AMERICA. MODELS SHOW SPLIT FLOW AS
HIGHLIGHTED BY A DEEPENING NORTHERN STREAM UPPER TROUGH INTO THE
NORTH-CENTRAL U.S. AND ENERGY/CLOSED LOW DEVELOPMENT IN A WELL
SEPARATED SOUTHERN STREAM FLOW TO OVER/OFFSHORE THE SOUTHWEST.
OPTED TO LIMIT DETERMINISTIC MODEL DETAIL AT THESE LESS CERTAIN
LONGER TIME FRAMES AND INSTEAD USE A BLEND OF BETTER COMPATIBLE
GEFS/ECMWF ENSEMBLE MEANS THAT SHOW THE WELL SPLIT FLOW THAT SEEMS
MORE IN LINE WITH HOLDING REINFORCING SOUTHERN STREAM ENERIES MORE
OFFSHORE. THIS PLAN ALSO ACTS TO BEST MAINTAIN WPC PRODUCT
CONTINUITY AND IS IN LINE WITH NATIONAL BLEND OF MODELS GUIDANCE.
..WEATHER/HAZARDS HIGHLIGHTS
AMPLIFIED EASTERN PACIFIC UPPER TROUGHING AND SYSTEM GENESIS WILL
WORK TOWARD THE WEST COAST. THIS IMPACTFUL EVENT WILL STEADILY
LOSE INFLUENCE BY FRIDAY AND ESPECIALLY INTO THE WEEKEND AS THE
SURFACE LOW/FRONTAL SYSTEM WORKS INLAND WITH UPPER TROUGH
PROGRESSION AND SHIFTS WITH FRONTAL PUSH. GIVEN PRECURSOR HEAVY
RAINFALL OVER THE NEXT FEW DAYS, A MARGINAL AND EMBEDDED SLIGHT
RISK ERO THREAT CONTINUES FOR FRIDAY FROM CENTRAL TO SOUTHERN
CALIFORNIA AND THE SOUTHERN GREAT BASIN. HIGHER ELEVATIONS OF THE
SIERRA SHOULD SEE AN EXTENDED HEAVY SNOW EVENT. ADDITIONALLY,
MOISTURE IS FORECAST TO SPILL OVER TO THE INTERMOUNTAIN WEST AND
NORTHERN/CENTRAL ROCKIES TO PRODUCE SOME TERRAIN ENHANCED HEAVY
SNOW AT HIGHER ELEVATIONS. SOME PRECIPITATION MAY CONTINUE ACROSS
PARTS OF THE SOUTHWEST INTO NEXT WEEK, BUT IS HIGHLY DEPENDENT ON
UNCERTAIN EVOLUTION OF A LINGERING CUTOFF LOW NEAR/OFF CALIFORNIA.
ELSEWHERE, LEADING SHALLOW SHORTWAVES MOVING THROUGH THE NORTHERN
TIER AND ASSOCIATED SURFACE SYSTEM REFLECTION AND POSSIBLE FLOW
AMPLIFICATION WITH THE DIGGING OF NORTHERN STREAM UPPER TROUGHING
INTO THE LOWER 48 WILL BRING GROWING PRECIPITATION CHANCES DOWN FROM
THE NORTH-CENTRAL U.S. TO THE GREAT LAKES, OHIO VALLEY, THE NORTH-
CENTRAL APPALACHIANS AND ACROSS THE NORTHERN MID-ATLANTIC AND
NORTHEAST TO INCLUDE MULTIPLE CHANCES FOR ENHANCED SNOW/ICE.
TEMPERATURES WILL CONTINUE TO BE ANOMALOUSLY WARM FROM THE CENTRAL
TO EAST-CENTRAL U.S. MID-LOWER LATITUDES INTO FRIDAY/SATURDAY.
DAYTIME HIGHS 25-30+ DEGREES ABOVE NORMAL MAY SET DAYTIME AND WARM
MORNING LOW RECORDS. THE AIRMASS MOVES EAST WITH TIME, MODERATING
AS IT REACHES THE EAST. AN AMPLIFIED SHORTWAVE INTO THE NORTHEAST
WILL BRING TEMPERATURES BACK BELOW NORMAL BY NEXT MONDAY. OUT WEST,
TEMPERATURES SHOULD MODERATE TOWARDS NORMAL THIS WEEKEND, WITH
ANOTHER WARMUP POSSIBLE EARLY NEXT WEEK AS UPPER RIDGING BUILDS IN.
LATER, THERE IS SOME GUIDANCE SIGNAL FAVORING RE-EMERGING HEAVIER
PRECIPITATION CHANCES INTO THE PACIFIC NORTHWEST/NORTHWEST WITH
RENEWED/WINDY ONSHORE FLOW IN ABOUT A WEEK LENDING INTO THE
CLIMATE PREDICTION CENTER'S WEEK 2 FORECAST TO RING IN 2026.
SCHICHTEL
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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