915
FXUS21 KWNC 301842
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 30 2025
SYNOPSIS: A SIGNIFICANT AND RAPID MID-LEVEL PATTERN CHANGE IS PREDICTED ACROSS
THE PACIFIC DURING THE WEEK-2 PERIOD. WHILE THIS FAVORS A WARMING TREND ACROSS
ALASKA, MODEL SOLUTIONS VARY REGARDING THE DOWNSTREAM RESPONSE ACROSS THE
CONTIGUOUS U.S. (CONUS) MAKING FOR A LOW CONFIDENCE AND CHALLENGING HAZARDS
OUTLOOK. CONTINUED ONSHORE FLOW ACROSS THE WESTERN CONUS EARLY IN THE PERIOD
FAVORS INCREASED CHANCES OF HEAVY PRECIPITATION (COASTAL RAIN AND HIGH
ELEVATION SNOW) NEAR THE WEST COAST. EAST OF THE ROCKIES, HIGH LATITUDE
BLOCKING COMBINED WITH PERIODIC SHORTWAVE DISTURBANCES COULD LEAD TO A MORE
ACTIVE WEATHER PATTERN DEPENDING ON WHERE VARIOUS FEATURES LINE UP.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF SOUTHERN AND CENTRAL
CALIFORNIA, WED-FRI, JAN 7-9.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE LOWER MISSISSIPPI
VALLEY, TENNESSEE VALLEY, AND SOUTHEAST, WED-FRI, JAN 7-9.
SLIGHT RISK OF HEAVY SNOW ACROSS PORTIONS OF THE KLAMATH AND SIERRA NEVADA
MOUNTAINS, WED-FRI, JAN 7-9.
SLIGHT RISK OF HEAVY SNOW ACROSS PORTIONS OF THE EASTERN GREAT LAKES,
NORTHEAST, AND CENTRAL APPALACHIANS, WED-FRI, JAN 7-9.
SLIGHT RISK OF HIGH WINDS ALONG THE WEST COAST, WED-FRI, JAN 7-9.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES ACROSS PORTIONS OF SOUTHWESTERN
MAINLAND ALASKA AND THE ALASKA PENINSULA, WED-TRU, JAN 7-8.
SLIGHT RISK OF HIGH WINDS ACROSS PORTIONS OF THE ALASKA PENINSULA, SOUTHERN
MAINLAND ALASKA, AND SOUTHEASTERN ALASKA, WED-FRI, JAN 7-9.
DETAILED SUMMARY
FOR FRIDAY JANUARY 02 - TUESDAY JANUARY 06:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY JANUARY 07 - TUESDAY JANUARY 13: DURING WEEK-2, THE 0Z ECMWF AND
CANADIAN ENSEMBLES DEPICT A QUICK MID-LEVEL PATTERN TRANSITION ACROSS THE
PACIFIC WITH A WEAKENING OF THE RIDGE TO THE SOUTH OF THE ALEUTIANS, TROUGHING
EMERGING ACROSS THE CENTRAL PACIFIC, AND RIDGING OVER THE WESTERN CONUS AND
EASTERN ALASKA BY THE END OF WEEK-2. THIS WOULD BE CONSISTENT WITH A WEAKENING
NEGATIVE PHASE OF THE PACIFIC NORTH AMERICAN (-PNA) PATTERN. WHILE THE 0Z GEFS
ALSO DEPICTS THIS TRANSITION TO SOME DEGREE, IT IS SLOWER AND MORE WEST-BASED
WITH THE TROUGH AND RIDGE FEATURES AT THE END OF THE PERIOD COMPARED TO THE
ECMWF AND CANADIAN.
TROUGHING NEAR THE WEST COAST OF THE CONUS AT THE OUTSET OF THE PERIOD FAVORS
CONTINUED CHANCES OF HEAVY PRECIPITATION. BOTH THE GEFS AND ECMWF PROBABILISTIC
EXTREMES TOOLS (PETS) DEPICT AT LEAST A 20 PERCENT CHANCE 3-DAY PRECIPITATION
TOTALS EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE OVER PORTIONS OF THE WEST
COAST EARLY IN WEEK-2, WITH THE ECMWF INDICATING GREATER THAN 40 PERCENT
CHANCES FOR EXCEEDING THE 85TH PERCENTILE OVER SOUTHERN CALIFORNIA.
UNCALIBRATED GUIDANCE FROM THE 0Z GEFS FAVORS A STRONGER MOISTURE SURGE INTO
SOUTHERN CALIFORNIA DUE TO A MORE SOUTHWARD DISPLACEMENT OF THE AMPLIFIED
TROUGH. HOWEVER, THE 0Z ECMWF AND CANADIAN ENSEMBLES FAVOR THE BULK OF THE
MOISTURE OVER THE PACIFIC NORTHWEST. PRECIPITATION TOTALS OVER THE PACIFIC
NORTHWEST ARE NOT LIKELY TO EXCEED HAZARDOUS THRESHOLDS, THEREFORE, A SLIGHT
RISK FOR HEAVY PRECIPITATION IS POSTED FOR PORTIONS OF CALIFORNIA SOUTH OF THE
BAY AREA, VALID JAN 7-9, WITH A CORRESPONDING SLIGHT RISK OF HEAVY SNOW ACROSS
HIGHER ELEVATIONS OF THE KLAMATH AND SIERRA NEVADA MOUNTAINS. HEAVY SNOW IS
ALSO POSSIBLE FURTHER INLAND ACROSS THE GREAT BASIN AND ROCKIES, ALTHOUGH
PROBABILITIES FOR DAILY SNOWFALL GREATER THAN 4 INCHES IN THE ECMWF AND GEFS
ENSEMBLES ARE LOWER COMPARED TO PROBABILITIES FARTHER WEST PRECLUDING AN
EXTENSION OF THE HAZARD. A SLIGHT RISK OF HIGH WINDS IS ALSO POSTED ALONG THE
ENTIRE WEST COAST FOR JAN 7-9, WITH THE ECMWF PET DEPICTING A ROBUST WIND
SIGNAL ACROSS THE NORTHWEST ASSOCIATED WITH THE STRONGEST ONSHORE FLOW EARLY IN
WEEK-2. HOWEVER, THE MUCH WEAKER GEFS ADDS TO THE UNCERTAINTY SUPPORTING ONLY A
SLIGHT RISK. WHILE ENHANCED PRECIPITATION MAY CONTINUE ACROSS THE NORTHWEST
LATER IN WEEK-2 BASED ON THE ECMWF INTEGRATED VAPOR TRANSPORT (IVT) TOOL, THE
POTENTIAL FOR A MORE AMPLIFIED RIDGE OVER THE WEST AS DEPICTED IN THE ECMWF AND
CANADIAN ENSEMBLES WOULD FAVOR LESS PRECIPITATION. AS A RESULT, THE ASSOCIATED
HAZARDS ARE NOT EXTENDED LATER INTO WEEK-2 AT THIS TIME.
FURTHER DOWNSTREAM ACROSS THE CONUS, MULTIPLE SHORTWAVE DISTURBANCES ARE LIKELY
TO PROPAGATE THROUGH THE MEAN FLOW. MODEL SOLUTIONS DEPICT PERIODS OF ENHANCED
PRECIPITATION ALONG A BAROCLINIC ZONE EXTENDING FROM THE GULF COAST
NORTHEASTWARD ALONG THE EASTERN SEABOARD. WHILE MODEL SPREAD REMAINS QUITE
HIGH, UNCALIBRATED PROBABILITIES FROM THE GEFS AND ECMWF INDICATE AT LEAST A
20% CHANCE OF 3-DAY SNOW ACCUMULATION TO EXCEED 4 INCHES FOR MUCH OF THE
NORTHEAST U.S. THIS SUPPORTS MAINTAINING THE SLIGHT RISK FOR HEAVY SNOW OVER
THESE AREAS, EXTENDING INTO THE CENTRAL APPALACHIANS, JAN 7-9. FURTHER SOUTH,
THE ECMWF AND GEFS PETS DEPICT AT LEAST A 20 PERCENT CHANCE 3-DAY PRECIPITATION
TOTALS EXCEED 1-INCH OVER PARTS OF THE LOWER MISSISSIPPI VALLEY, TENNESSEE
VALLEY, AND SOUTHEAST, ALTHOUGH THE SIGNALS ARE WEAKER THAN YESTERDAY IN
PERCENTILE SPACE. BASED ON CONTINUITY, A SLIGHT RISK OF HEAVY PRECIPITATION
REMAINS IN PLACE, JAN 7-9. THE NORTHWARD TRAJECTORY OF THIS MOISTURE IS
UNCERTAIN, ALTHOUGH A SUBSTANTIAL HIGH-LATITUDE BLOCKING RIDGE PREDICTED OVER
NORTHEASTERN NORTH AMERICA COULD RESULT IN A MORE SIGNIFICANT SYNOPTIC SYSTEM
ACROSS THE EASTERN HALF OF THE CONUS TOWARD THE SECOND HALF OF WEEK-2 DEPENDING
ON THE ALIGNMENT AND AMPLITUDE OF SHORTWAVE FEATURES.
SURFACE LOW PRESSURE FORECAST OVER THE GULF OF ALASKA AND RELATIVELY HIGHER
PRESSURES OVER MAINLAND ALASKA FAVOR A STRONG PRESSURE GRADIENT OVER SOUTHERN
ALASKA. THIS RESULTS IN ELEVATED CHANCES FOR EPISODES OF HIGH WINDS ACROSS THE
ALASKA PENINSULA EASTWARD THROUGH SOUTHEAST ALASKA. HIGH WINDS WOULD BE
PARTICULARLY FAVORED IN GAPS AND INLETS. THE PETS DEPICT AT LEAST A 20 PERCENT
CHANCE WIND SPEEDS EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE AND 40-MPH OVER
SOME OF THESE AREAS EARLY IN THE PERIOD. THERE IS STILL SOME SIGNAL FOR HIGH
WINDS THROUGH THE END OF WEEK-2, BUT GIVEN INCREASING MODEL SPREAD AND A
TRANSITIONING PATTERN THERE IS INSUFFICIENT CONFIDENCE TO ISSUE AN EXTENDED
HAZARD. THEREFORE A SLIGHT RISK OF HIGH WINDS IS POSTED FOR MOST OF SOUTHERN
AND SOUTHEASTERN ALASKA FOR JAN 7-9.
THE MID-LEVEL PATTERN TRANSITION FAVORS A MODERATION OF PERSISTENTLY COLD
TEMPERATURES ACROSS ALASKA. WHILE SIGNALS IN THE ECMWF AND GEFS PETS REMAIN
ELEVATED OVER SOUTHWESTERN ALASKA, ACTUAL TEMPERATURES ARE BECOMING LESS LIKELY
TO REACH HAZARDS THRESHOLDS, WITH POSITIVE TEMPERATURE ANOMALIES EMERGING OVER
MOST OF THE STATE BY THE END OF THE PERIOD. AS A RESULT, THE MODERATE RISK FOR
MUCH BELOW NORMAL TEMPERATURES WAS DISCONTINUED YESTERDAY, WHILE A SLIGHT RISK
REMAINS POSTED ACROSS SOUTHWESTERN MAINLAND ALASKA THROUGH JAN 8. SOME INTERIOR
AREAS MAY EXPERIENCE MINIMUM TEMPERATURES BELOW -10 DEG F, ALTHOUGH THE ALASKA
PENINSULA AND SOUTHERN COAST ARE MORE LIKELY TO HAVE MINIMUM TEMPERATURES IN
THE POSITIVE SINGLE DIGITS OR TEENS. 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.
FORECASTER: DANNY BARANDIARAN
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page