690
FXUS21 KWNC 071918
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 07 2025
SYNOPSIS: MID-LEVEL LOW PRESSURE ACROSS THE NORTHEASTERN PACIFIC AND EASTERN
ALASKA DOWNSTREAM FROM A STRONG MID-LEVEL HIGH PRESSURE RIDGE CENTERED JUST
WEST OF THE ALASKA MAINLAND ARE FORECAST TO BRING VERY COLD AIR AND DANGEROUS
WIND CHILLS ACROSS CENTRAL AND SOUTHERN ALASKA, ALONG WITH EPISODES OF HIGH
WINDS ACROSS SOUTHERN ALASKA FROM THE ALEUTIANS INTO SOUTHEAST ALASKA. ENHANCED
ONSHORE FLOW INTO THE NORTHWESTERN CONTIGUOUS U.S. (CONUS) IS FORECAST BY THE
START OF WEEK-2 WITH MID-LEVEL LOW AND HIGH PRESSURE TO THE NORTH AND SOUTH OF
THE REGION, RESPECTIVELY. IN THE EASTERN CONUS, AN AREA OF ARCTIC SURFACE HIGH
PRESSURE IS FORECAST TO BRING ENHANCED CHANCES FOR MUCH BELOW NORMAL
TEMPERATURES FOR MANY AREAS EAST OF THE MISSISSIPPI EARLY IN WEEK-2.
THEREAFTER, INCREASED RETURN FLOW FROM THE GULF IS EXPECTED TO MODERATE
TEMPERATURES.
HAZARDS
MODERATE RISK OF HIGH WINDS ACROSS SOUTHERN ALASKA FROM THE EASTERN ALEUTIANS
THROUGH CENTRAL SOUTHEAST ALASKA, MON-SUN, DEC 15-21.
SLIGHT RISK OF HIGH WINDS FOR SOUTHERN ALASKA FROM THE CENTRAL ALEUTIANS
THROUGH SOUTHEAST ALASKA, MON-SUN, DEC 15-21.
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR MOST OF SOUTHEAST ALASKA,
MON, DEC 15.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR MUCH OF CENTRAL, EASTERN, AND
SOUTHERN ALASKA, MON-WED, DEC 15-17.
MODERATE RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF THE OHIO AND
TENNESSEE VALLEYS, AND APPALACHIANS, MON, DEC 15.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF THE MISSISSIPPI,
OHIO, AND TENNESSEE VALLEYS, APPALACHIANS, GREAT LAKES, MID-ATLANTIC, AND
SOUTHEAST, MON, DEC 15
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE PACIFIC NORTHWEST AND
NORTHERN CALIFORNIA, MON-FRI, DEC 15-19.
SLIGHT RISK OF HEAVY SNOW ACROSS THE CASCADES, NORTHERN SIERRA NEVADA AND
KLAMATH RANGES, MON-FRI, DEC 15-19.
SLIGHT RISK OF HEAVY SNOW ACROSS PART OF THE NORTHERN ROCKIES AND ADJACENT HIGH
PLAINS, MON-FRI, DEC 15-19.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE PACIFIC NORTHWEST AND NORTHERN
CALIFORNIA, MON-FRI, DEC 15-19.
FLOODING POSSIBLE ACROSS PARTS OF THE PACIFIC NORTHWEST.
DETAILED SUMMARY
FOR WEDNESDAY DECEMBER 10 - SUNDAY DECEMBER 14:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR MONDAY DECEMBER 15 - SUNDAY DECEMBER 21: THE 0Z ECWMF, GEFS, AND CANADIAN
ENSEMBLES DEPICT A HIGHLY-AMPLIFIED MID-LEVEL RIDGE CENTERED WEST OF ALASKA,
WITH AN AMPLIFIED DOWNSTREAM MID-LEVEL TROUGH ESTABLISHED OVER SOUTHEASTERN
ALASKA AND THE ADJACENT NORTHEASTERN PACIFIC. THIS SET-UP FAVORS PERSISTENT
SURFACE HIGH PRESSURE 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 BETWEEN THE EASTERN ALEUTIAN ISLANDS
THROUGH MUCH OF 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, BROAD
MODERATE AND SLIGHT RISKS OF HIGH WINDS ARE POSTED FOR ALL OF WEEK-2 FOR MUCH
OF SOUTHERN ALASKA.
PETS CONTINUE TO HIGHLIGHT ENHANCED CHANCES FOR TEMPERATURES TO FALL TO NEAR
HAZARDOUS THRESHOLDS ACROSS SOUTHEAST ALASKA AND INTO THE SOUTHEASTERN
MAINLAND. HOWEVER, CHANCES FOR HAZARDOUS MUCH BELOW NORMAL TEMPERATURES ARE
REDUCED BY THE MIDDLE OF WEEK-2 AND FURTHER REDUCED BY THE END OF THE PERIOD.
THIS IS TIED TO THE MID-LEVEL 500-HPA HEIGHT PATTERN DEAMPLIFYING OVER ALASKA
THROUGH THE PERIOD RESULTING IN LESS NORTHERLY FLOW INTO THE STATE. HOWEVER,
TODAY'S FORECAST GUIDANCE INDICATES THE MORE AMPLIFIED MID-LEVEL PATTERN TO
PERSIST LONGER INTO WEEK-2 RELATIVE TO YESTERDAY. THEREFORE, THERE IS MORE
UNCERTAINTY ON THE ENDING OF ANY POTENTIAL TEMPERATURE HAZARDS BUT FOR NOW A
MODERATE RISK REMAINS POSTED FOR SOUTHEAST ALASKA FOR DAY 8, CONSISTENT WITH
YESTERDAY, WHILE A BROADER SLIGHT RISK IS MAINTAINED FOR MUCH OF THE INTERIOR,
SOUTH-CENTRAL, AND SOUTHEASTERN MAINLAND FOR DAYS 8-10. HOWEVER, THIS MAY NEED
TO BE RE-EVALUATED TOMORROW TO DETERMINE IF THESE HAZARDS SHOULD PERSIST LONGER
INTO WEEK-2. 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.
IN THE WAKE OF A STRONG MID-LEVEL TROUGH PROGRESSING OFF THE NORTHEAST COAST,
STRONG ARCTIC HIGH PRESSURE BUILDS INTO THE EASTERN CONUS BY THE END OF WEEK-1
AND INTO WEEK-2. PETS FROM THE ECENS AND CMCE INDICATE ENHANCED CHANCES FOR
TEMPERATURES TO FALL BELOW THE 2ND PERCENTILE AT THE START OF WEEK-2 OVER THE
OHIO AND TENNESSEE VALLEYS. THERE IS BROAD SUPPORT AMONG ALL THREE PETS FOR
MINIMUM TEMPERATURES TO FALL BELOW THE 5TH PERCENTILE ACROSS MUCH OF THE
EASTERN CONUS. THEREFORE, A MODERATE RISK OF MUCH BELOW-NORMAL TEMPERATURES IS
FORECAST FOR PARTS OF THE OHIO AND TENNESSEE VALLEYS ALONG WITH PARTS OF THE
APPALACHIANS FOR DAY 8. ENVELOPING THIS MODERATE RISK AREA, A BROAD SLIGHT RISK
OF MUCH BELOW NORMAL TEMPERATURES IS FORECAST FOR THE MIDDLE AND LOWER
MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, MID-ATLANTIC, AND SOUTHEAST ALSO FOR
DAY 8. THE GEFS AND ECENS INDICATE ENHANCED PROBABILITIES FOR APPARENT
TEMPERATURES TO FALL BELOW ZERO ACROSS MUCH OF THE NORTHERN HALF OF THE
MODERATE RISK AREA WITH NEAR 0 DEGF WIND CHILLS OVER THE SOUTHERN HALF OF THE
REGION. FREEZING TEMPERATURES ARE LIKELY TO EXTEND TO THE GULF COAST AND
THROUGH MUCH OF THE FLORIDA PENINSULA.
TEMPERATURES SHOULD MODERATE RELATIVELY RAPIDLY AS WE HEAD INTO THE MIDDLE OF
THE PERIOD AS THE HIGH PRESSURE SHIFTS EAST, ALLOWING RETURN FLOW FROM THE GULF
INTO CENTRAL CONUS. THE RETURN FLOW INCREASES CHANCES FOR PRECIPITATION TO
IMPACT PARTS OF THE LOWER MISSISSIPPI, TENNESSEE, AND OHIO VALLEYS BY THE
MIDDLE OF THE PERIOD. THERE REMAIN DIFFERENCES IN TIMING, LOCATION, AND
PRECIPITATION AMOUNT BETWEEN THE VARIOUS ENSEMBLE GUIDANCE. SUBSEQUENTLY, NO
HAZARD IS POSTED AT THIS TIME BUT BEARS WATCHING.
A MID-LEVEL RIDGE OVER THE WESTERN CONUS HAS TRENDED WEAKER AND FLATTER
RELATIVE TO YESTERDAY. THIS HAS INCREASED CHANCES FOR ENHANCED ONSHORE FLOW
INTO NORTHERN CALIFORNIA AND THE PACIFIC NORTHWEST SINCE YESTERDAY'S FORECAST.
PETS AND RAW GUIDANCE SHOWS SIGNIFICANTLY HIGHER CHANCES FOR ENHANCED
PRECIPITATION INTO THE REGION FOR MUCH OF THE WEEK-2 PERIOD. THIS IS QUITE A
DRAMATIC DIFFERENCE IN FORECAST GUIDANCE RELATIVE TO YESTERDAY AND MODELS DO
NOT SEEM TO HAVE A GOOD HANDLE ON THE HEIGHT PATTERN. THEREFORE, DESPITE SOME
TOOLS INDICATING 40-50% CHANCES OF PRECIPITATION EXCEEDING THE 85TH
CLIMATOLOGICAL PERCENTILE, NO MODERATE RISK HAZARDS ARE POSTED TODAY. HOWEVER,
A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED FOR MUCH OF NORTHERN CALIFORNIA
AND WESTERN WASHINGTON AND OREGON FOR DAYS 8-12. A CORRESPONDING SLIGHT RISK OF
HIGH WINDS IS POSTED FOR MUCH OF THE SAME REGION DURING THIS PERIOD. THIRD, A
SLIGHT RISK OF HEAVY SNOW IS POSTED FOR THE NORTHERN SIERRA NEVADA, KLAMATH AND
CASCADES RANGES ALONG WITH A SEPARATE SLIGHT RISK OF HEAVY SNOW FOR THE
NORTHERN ROCKIES AS THE MOISTURE MOVES INLAND FOR DAYS 8-12. FINALLY, A
FLOODING POSSIBLE HAZARD REMAINS POSTED FOR PORTIONS OF WESTERN WASHINGTON AND
NORTHERN OREGON, WHERE ANY ADDITIONAL PRECIPITATION MAY INCREASE THE RISK FOR
FLOODING AND LANDSLIDES AS THE SOIL CONDITIONS WILL REMAIN WET FROM AN
ATMOSPHERIC RIVER IN WEEK-1.
FORECASTER: RYAN BOLT
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