828
FXUS21 KWNC 131841
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 13 2025
SYNOPSIS: STRONG MID-LEVEL AND SURFACE LOW PRESSURE OVER THE NORTH PACIFIC
BRING THE POTENTIAL FOR A VARIETY OF HAZARDOUS WEATHER INCLUDING HIGH WINDS,
HEAVY PRECIPITATION, AND HIGH-ELEVATION SNOW ACROSS THE WESTERN CONTIGUOUS U.S.
(CONUS) THROUGHOUT THE WEEK-2 PERIOD. SURFACE LOW PRESSURE OVER THE GREAT
PLAINS ALONG WITH SURFACE HIGH PRESSURE OVER THE SOUTHEAST U.S. PAIR TO PRODUCE
POTENTIALLY HAZARDOUS WINDS OVER MUCH OF THE PLAINS, UPPER MISSISSIPPI VALLEY,
AND GREAT LAKES. STRONG SURFACE HIGH PRESSURE OVER THE YUKON IS FAVORED TO PUSH
EXTREMELY COLD AIR INTO SOUTHEASTERN ALASKA, POTENTIALLY REACHING HAZARDOUS
CRITERIA.
HAZARDS
MODERATE RISK OF HEAVY SNOW FOR THE OREGON CASCADES, KLAMATH, AND NORTHERN AND
CENTRAL SIERRA NEVADAS, SUN-SAT, DEC 21-27.
MODERATE RISK OF HEAVY SNOW FOR MUCH OF THE ROCKIES, AND THE WASATCH RANGE,
SUN-THU, DEC 21-25.
SLIGHT RISK OF HEAVY SNOW FOR THE CASCADES, KLAMATH, AND SIERRA NEVADAS,
SUN-SAT, DEC 21-27.
SLIGHT RISK OF HEAVY SNOW FOR THE ROCKIES AND THE RANGES OF THE GREAT BASIN,
SUN-SAT, DEC 21-27.
MODERATE RISK OF HEAVY PRECIPITATION OF PORTIONS OF NORTHERN CALIFORNIA AND
SOUTHWESTERN OREGON, SUN-SAT, DEC 21-27.
MODERATE RISK OF HEAVY PRECIPITATION FOR COASTAL PORTIONS OF CENTRAL AND
SOUTHERN CALIFORNIA, SUN-THU, DEC 21-25.
SLIGHT RISK OF HEAVY PRECIPITATION ALONG THE ENTIRE WEST COAST, SUN-SAT, DEC
21-27.
MODERATE RISK OF HIGH WINDS FOR MUCH OF NORTHERN CALIFORNIA, THE PACIFIC
NORTHWEST, NORTHERN GREAT BASIN, AND NORTHERN ROCKIES, SUN-SAT, DEC 21-27.
SLIGHT RISK OF HIGH WINDS FOR MUCH OF CALIFORNIA, PACIFIC NORTHWEST, GREAT
BASIN, NORTHERN ROCKIES, NORTHERN AND CENTRAL PLAINS, MIDDLE AND UPPER
MISSISSIPPI VALLEY, AND GREAT LAKES, SUN-SAT, DEC 21-27.
SLIGHT RISK OF HIGH WINDS FOR THE ALASKA PENINSULA, SOUTHERN MAINLAND ALASKA,
AND SOUTHEASTERN SUN-SAT, DEC 21-27.
MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR SOUTHEASTERN ALASKA,
SUN-WED, DEC 21-24.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES FOR MUCH OF SOUTH-CENTRAL AND
SOUTHEASTERN ALASKA, SUN-SAT, DEC 21-27.
FLOODING POSSIBLE ALONG THE WEST COAST FROM PUGET SOUND TO SAN FRANCISCO BAY.
DETAILED SUMMARY
FOR TUESDAY DECEMBER 16 - SATURDAY DECEMBER 20:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SUNDAY DECEMBER 21 - SATURDAY DECEMBER 27: TODAY'S MODEL SOLUTIONS CONTINUE
TO DEPICT WITH EXCELLENT AGREEMENT REGARDING AN ACTIVE AND PERSISTENT SYNOPTIC
PATTERN OVER THE NORTH PACIFIC AND WESTERN NORTH AMERICA. THE 0Z ECMWF, GEFS,
AND CANADIAN ENSEMBLES DEPICT AN AMPLIFIED MID-LEVEL RIDGE CENTERED OVER THE
BERING SEA, WITH AN AMPLIFIED DOWNSTREAM MID-LEVEL TROUGH EXTENDING FROM THE
NORTH PACIFIC ACROSS THE PACIFIC NORTHWEST AND INTO THE HIGH LATITUDES OF
CANADA. AT THE SURFACE, HIGH PRESSURE PERSISTS ACROSS MUCH OF ALASKA AND THE
YUKON THROUGHOUT WEEK-2. CONVERSELY, MEAN LOW PRESSURE IS FAVORED IN THE GULF
OF ALASKA. THE PRESSURE GRADIENT BETWEEN THESE FEATURES BRINGS INCREASED
CHANCES FOR EPISODES OF HIGH WINDS ACROSS MUCH OF SOUTHERN ALASKA FROM THE
CENTRAL ALEUTIAN ISLANDS THROUGH SOUTHEAST ALASKA. HIGH WINDS WOULD BE
PARTICULARLY FAVORED IN GAPS AND INLETS. PROBABILISTIC EXTREMES TOOLS (PETS)
SHOW ENHANCED CHANCES OF WIND SPEEDS EXCEEDING THE 85TH CLIMATOLOGICAL
PERCENTILE. THEREFORE, A SLIGHT RISK OF HIGH WINDS IS POSTED FOR MOST OF
SOUTHERN AND SOUTHEASTERN ALASKA FOR ALL OF WEEK-2.
PETS CONTINUE TO HIGHLIGHT ENHANCED CHANCES FOR TEMPERATURES TO FALL TO NEAR
HAZARDOUS THRESHOLDS ACROSS PORTIONS OF SOUTH-CENTRAL, INTERIOR, AND SOUTHEAST
ALASKA. AS THE BERING SEA RIDGE SLOWLY WEAKENS, THE ANOMALOUS COLD (AND
ASSOCIATED NORTHERLY FLOW) WILL GRADUALLY EXPAND WESTWARD ACROSS THE STATE. A
MODERATE RISK IS POSTED FOR SOUTHEAST ALASKA FOR DEC 21-24, WHILE A BROADER
SLIGHT RISK IS MAINTAINED FOR MUCH OF SOUTH-CENTRAL AND SOUTHEAST ALASKA FOR
ALL OF WEEK-2. TEMPERATURES BETWEEN -20 DEG F AND -35 DEG F ARE PREDICTED TO BE
WIDESPREAD ACROSS MUCH OF INLAND ALASKA, WITH -40 DEG F TEMPERATURES INDICATED
BY THE PETS OVER THE EASTERN INTERIOR TO THE NORTH OF FAIRBANKS. CLOSER TO THE
COAST, TEMPERATURES ARE EXPECTED TO RANGE BETWEEN 0 AND -15 DEG F (ANCHORAGE
NEAR -10 DEG F), WHILE THE SOUTHERN HALF OF SOUTHEAST ALASKA IS PREDICTED TO BE
SOMEWHAT MILDER, WITH HIGH TEMPERATURES ABOUT +10 DEG F. THE COMBINATION OF
VERY COLD WEATHER AND HIGH WINDS ALONG THE SOUTHERN TIER OF THE STATE INCREASES
THE THREAT FOR HEAVY FREEZING SPRAY AT TIMES NEAR LARGER BODIES OF WATER.
THE 0Z ECENS, 0Z GEFS, AND 0Z CMCE MODEL SOLUTIONS DEPICT PERSISTENT MID-LEVEL
TROUGHING OVER THE NORTH PACIFIC AND BROAD POSITIVE 500-HPA HEIGHT ANOMALIES
ACROSS MUCH OF THE SOUTHERN CONUS, RESULTING IN AN ENHANCED JET STREAM OVER THE
PACIFIC NORTHWEST. THE INTEGRATED VAPOR TRANSPORT (IVT) TOOL ALSO INDICATES
DEEP LOW-LEVEL MOISTURE STREAMING INTO THE WEST COAST THROUGHOUT THE FORECAST
PERIOD, WITH BOTH THE ECMWF AND GEFS SHOWING PROBABILITIES ABOVE 40% EARLY IN
THE WEEK FOR IVT TO EXCEED 250 KG/M/S. TODAY FORECAST SOLUTIONS DEPICT A DEEPER
TROUGH OVER THE WEST COAST AND A CONTINUED SHIFT SOUTHWARD OF THE MOST INTENSE
PRECIPITATION. THE PETS AND UNCALIBRATED PRECIPITATION GUIDANCE SUPPORTS A
SLIGHT RISK OF HEAVY PRECIPITATION ALONG THE ENTIRE WEST COAST FOR ALL OF
WEEK-2. A MODERATE RISK FOR HEAVY PRECIPITATION IS INDICATED FOR SOUTHWESTERN
OREGON AS WELL AS PORTIONS OF NORTHERN AND CENTRAL CALIFORNIA, ALSO FOR ALL OF
WEEK-2. PRECIPITATION AMOUNTS OF 2 INCHES ARE PREDICTED BY PET GUIDANCE WITHIN
THIS BROAD REGION OF ELEVATED ONSHORE FLOW FROM WASHINGTON STATE SOUTHWARD TO
CENTRAL CALIFORNIA. BOTH THE GEFS AND ECMWF INDICATE AR ACTIVITY TO SHIFT BACK
NORTH BY THE END OF WEEK-2, AND THE POTENTIAL FOR HEAVY PRECIPITATION WITH IT,
THEREFORE A MODERATE RISK OF HEAVY PRECIPITATION IS POSTED FOR COASTAL PORTIONS
OF CENTRAL AND SOUTHERN CALIFORNIA FOR DEC 21-25. THIS FORECASTED HEAVY
PRECIPITATION, IN ADDITION TO THE ANTECEDENT WEEK-1 PRECIPITATION, IS LIKELY TO
AGGRAVATE FLOODING ISSUES FOR THE PACIFIC NORTHWEST, WITH A FLOODING POSSIBLE
HAZARD POSTED WEST OF THE COASTAL RANGES FROM PUGET SOUND TO SAN FRANCISCO BAY.
CONTINUED PRECIPITATION ACCUMULATIONS ON SATURATED SOILS ALSO BRING THE
ADDITIONAL RISKS OF LANDSLIDES AND DEBRIS FLOWS IN STEEP TERRAIN OR BURN SCARS,
AS WELL AS THE POTENTIAL FOR URBAN AND FLASH FLOODING ACROSS THE WEST COAST.
THE INCOMING MOISTURE ASSOCIATED WITH THIS ATMOSPHERIC RIVER IS LIKELY TO PUSH
WELL INLAND, RESULTING IN POTENTIALLY HEAVY SNOW FOR MANY MOUNTAIN RANGES
ACROSS THE WEST. UNCALIBRATED PROBABILITIES FROM BOTH THE ECENS AND GEFS FOR
DAILY ACCUMULATIONS OF OVER 6 INCHES EXCEED 40% IN SOME LOCATIONS THROUGHOUT
THE WEEK, AND THE GEFS PET FOR SNOW WATER EQUIVALENT (SWE) INDICATES AT LEAST A
20% CHANCE OF 3-DAY SWE TO EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE AND AT
LEAST 1 INCH FOR MUCH OF THE SOUTHERN CASCADES, SIERRAS, AND NORTHERN AND
CENTRAL ROCKIES THROUGHOUT THE WEEK. BASED ON THE GEFS PET AND UNCALIBRATED
DAILY SNOWFALL TOTALS, A MODERATE RISK OF HEAVY SNOW IS POSTED FOR ALL OF
WEEK-2 FOR THE OREGON CASCADES, KLAMATH, AND NORTHERN AND CENTRAL SIERRAS, AND
A SLIGHT RISK OF HEAVY SNOW EXTENDING OVER THE SOUTHERN SIERRAS, ALSO FOR THE
WHOLE WEEK. FURTHER EAST, A BROAD AREA ENCOMPASSING THE ROCKY MOUNTAINS AND THE
CENTRAL GREAT BASIN IS INDICATED FOR A SLIGHT RISK OF HEAVY SNOW THROUGHOUT THE
FORECAST PERIOD. ADDITIONALLY, A MODERATE RISK IS POSTED FOR MUCH OF THE
ROCKIES, AND THE WASATCH, VALID DEC 21-25. UNCALIBRATED PROBABILITIES FROM THE
GEFS AND ECMWF EXCEED 40% AT THE 1-FOOT ACCUMULATION THRESHOLD EARLY IN THE
FORECAST PERIOD FOR THESE REGIONS THEN STEADILY DECLINE AS THE WEEK PROGRESSES.
ALONG WITH HEAVY PRECIPITATION AND SNOW, HIGH WINDS REACHING HAZARDOUS CRITERIA
ARE ALSO POSSIBLE ASSOCIATED WITH THIS ATMOSPHERIC RIVER (AR) EVENT. THIS IS
WELL INDICATED BY THE ECMWF AND GEFS PETS WHICH INDICATE AT LEAST A 20% CHANCE
OF 3-DAY MAXIMUM WIND SPEEDS EXCEEDING THE 85TH PERCENTILE FOR MUCH OF THE
CONUS THROUGHOUT THE WEEK. OVER THE WESTERN CONUS, ENHANCED WINDS ARE LIKELY
THE RESULT OF DEEP TROUGHING AND AR OVER THE WEST COAST, WHILE PERIODS OF
SURFACE LOW PRESSURE OVER THE PLAINS AND HIGH PRESSURE OVER THE SOUTHEAST U.S.
ARE THE FEATURES ENHANCING WINDS ELSEWHERE. A SLIGHT RISK OF HIGH WINDS IS
POSTED FOR MOST OF THE WESTERN CONUS AS WELL AS THE NORTHERN AND CENTRAL PLAINS
AND GREAT LAKES REGIONS FOR ALL OF WEEK-2. THE ECMWF PET IS ESPECIALLY BULLISH,
WITH PROBABILITIES EXCEEDING 80% FOR MUCH OF THE NORTHWESTERN CONUS EARLY IN
WEEK-2, FURTHER BACKED BY PATTERN RECOGNITION, WARRANTING A MODERATE RISK OF
HIGH WINDS FOR MUCH OF THE PACIFIC NORTHWEST, NORTHERN GREAT BASIN, AND
NORTHERN ROCKIES, ALSO FOR THE WHOLE FORECAST PERIOD.
FORECASTER: DANNY BARANDIARAN
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