404
FXUS21 KWNC 291936
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 29 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 ACROSS THE WEST COAST OF THE CONUS, TUE-THU,
JAN 6-8.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE LOWER MISSISSIPPI
VALLEY, TENNESSEE VALLEY, AND SOUTHEAST, TUE-SAT, JAN 6-10.
SLIGHT RISK OF HEAVY SNOW ACROSS PORTIONS OF THE CASCADES, KLAMATH, AND SIERRA
NEVADA MOUNTAINS, TUE-THU, JAN 6-8.
SLIGHT RISK OF HEAVY SNOW ACROSS PORTIONS OF THE EASTERN GREAT LAKES,
NORTHEAST, AND CENTRAL APPALACHIANS, TUE-THU, JAN 6-8.
SLIGHT RISK OF HIGH WINDS ACROSS MUCH OF THE CONUS WEST OF THE ROCKIES,
TUE-THU, JAN 6-8.
SLIGHT RISK OF MUCH BELOW-NORMAL TEMPERATURES ACROSS PORTIONS OF SOUTHWESTERN
MAINLAND ALASKA AND THE ALASKA PENINSULA, TUE-THU, JAN 6-8.
SLIGHT RISK OF HIGH WINDS ACROSS PORTIONS OF THE ALASKA PENINSULA, SOUTHERN
MAINLAND ALASKA, AND SOUTHEASTERN ALASKA, TUE-THU, JAN 6-8.
DETAILED SUMMARY
FOR THURSDAY JANUARY 01 - MONDAY JANUARY 05:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY JANUARY 06 - MONDAY JANUARY 12: 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 AND 1-INCH ACROSS THE ENTIRE
WEST COAST EARLY IN WEEK-2, WITH 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.
THEREFORE, A BROAD SLIGHT RISK FOR HEAVY PRECIPITATION IS POSTED ACROSS THE
ENTIRE WEST COAST, VALID JAN 6-8, WITH A CORRESPONDING SLIGHT RISK OF HEAVY
SNOW ACROSS HIGHER ELEVATIONS OF THE CASCADES, 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 ACROSS PARTS OF THE WESTERN CONUS, JAN 6-8, 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. MANY OF TODAY'S DETERMINISTIC SOLUTIONS ARE
NOT AS ROBUST REGARDING AN INITIAL NORTHERN STREAM SURFACE LOW AT THE OUTSET OF
THE PERIOD (JAN 6) COMPARED TO YESTERDAY, ALTHOUGH PROBABILITIES FOR SNOWFALL
GREATER THAN 4 INCHES DURING THE FIRST 3 DAYS OF THE PERIOD EXCEED 20 PERCENT
IN BOTH THE 0Z ECMWF AND GEFS ENSEMBLES ACROSS PARTS THE NORTHEAST AND EASTERN
GREAT LAKES LIKELY TIED TO ANOTHER SYSTEM AROUND DAY-10 (JAN 8). THIS SUPPORTS
MAINTAINING THE SLIGHT RISK FOR HEAVY SNOW OVER THESE AREAS, EXTENDING INTO THE
CENTRAL APPALACHIANS, JAN 6-8. 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 6-10. 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 THROUGH THE MIDDLE OF THE PERIOD. THERE IS STILL SOME
SIGNAL FOR HIGH WINDS AT THE END OF WEEK-2, BUT GIVEN INCREASING MODEL SPREAD
AND A TRANSITIONING PATTERN THERE IS INSUFFICIENT CONFIDENCE TO ISSUE A
FULL-WEEK HAZARD. THEREFORE A SLIGHT RISK OF HIGH WINDS IS POSTED FOR MOST OF
SOUTHERN AND SOUTHEASTERN ALASKA FOR JAN 6-8.
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 IS DISCONTINUED, WITH A SLIGHT RISK 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: THOMAS COLLOW
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