202
FXUS21 KWNC 071911
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST NOVEMBER 07 2025
SYNOPSIS: MID-LEVEL LOW PRESSURE IS FORECAST TO APPROACH THE WEST COAST LATER
NEXT WEEK AND THEN EVENTUALLY SHIFT EASTWARD OVER THE WEST BY NOVEMBER 17 OR
18. THIS WOULD INCREASE THE RISK OF MULTIPLE HAZARDS FROM THE WEST COAST TO
INLAND AREAS OF THE WEST. LOW PRESSURE DEVELOPMENT IS EXPECTED TO OCCUR ACROSS
THE GREAT PLAINS DURING WEEK-2 AND MOVE EASTWARD. THIS SYSTEM MAY BRING
INCREASED CHANCES FOR HEAVY PRECIPITATION TO PARTS OF THE LOWER MISSISSIPPI AND
TENNESSEE VALLEYS. DESPITE FAVORED WETNESS THROUGHOUT SOUTHERN ALASKA FROM
NOVEMBER 15-21, PRECIPITATION AMOUNTS ARE EXPECTED TO REMAIN BELOW HAZARDOUS
THRESHOLDS.
HAZARDS
MODERATE RISK OF HEAVY PRECIPITATION FOR SOUTHERN CALIFORNIA, SAT, NOV 15.
MODERATE RISK OF HEAVY PRECIPITATION FOR THE FOOTHILLS OF THE SIERRA NEVADA
MOUNTAINS, SAT-SUN, NOV 15-16.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF CALIFORNIA AND THE PACIFIC
NORTHWEST, SAT-SUN, NOV 15-16.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF ARIZONA, SAT-SUN, NOV 15-16.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE LOWER MISSISSIPPI,
TENNESSEE, AND OHIO VALLEYS, MON-WED, NOV 17-19.
MODERATE RISK OF HEAVY SNOW FOR THE SIERRA NEVADA MOUNTAINS, SAT-SUN, NOV 15-16.
SLIGHT RISK OF HEAVY SNOW FOR PORTIONS OF THE CASCADES, SIERRA NEVADA, AND
KLAMATH MOUNTAINS, SAT-SUN, NOV 15-16.
SLIGHT RISK OF HEAVY SNOW FOR PORTIONS OF THE NORTHERN AND CENTRAL ROCKIES AND
WASATCH RANGE, SAT-TUE, NOV 15-18.
SLIGHT RISK OF HEAVY SNOW FOR THE MOGOLLON RIM OF ARIZONA, SAT-SUN, NOV 15-16.
SLIGHT RISK OF HIGH WINDS FROM THE ROCKIES TO THE GREAT PLAINS AND UPPER
MISSISSIPPI VALLEY, SAT-WED, NOV 15-19.
DETAILED SUMMARY
FOR MONDAY NOVEMBER 10 - FRIDAY NOVEMBER 14:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY NOVEMBER 15 - FRIDAY NOVEMBER 21: A MID-LEVEL TROUGH IS FORECAST
TO MOVE ONSHORE THE WEST COAST AT THE END OF WEEK-1 OR EARLY IN WEEK-2
CONTINUING THE PERIOD OF ACTIVE WEATHER ACROSS THE WEST. THE GEFS, ECENS, AND
CMCE CONTINUE TO PREDICT A DEEP TROUGH SUPPORTING INCREASED CHANCES OF HEAVY
PRECIPITATION ACROSS PORTIONS OF CALIFORNIA. THE PROBABILISTIC EXTREMES TOOL
(PET) BASED ON THE ECENS DEPICTS 20-40% CHANCES OF 3 DAY PRECIPITATION AMOUNTS
EXCEEDING 1 INCH ACROSS PARTS OF SOUTHERN CALIFORNIA. RAW GUIDANCE FROM THE
ECENS CONTINUES TO INDICATE ELEVATED CHANCES FOR MORE THAN 1 INCH OF
PRECIPITATION ACROSS PARTS OF SOUTHERN CALIFORNIA, AS WELL. THEREFORE, DESPITE
RELATIVELY WEAKER GEFS BASED TOOLS, A MODERATE RISK OF HEAVY PRECIPITATION
REMAINS IN PLACE ACROSS PARTS OF SOUTHERN CALIFORNIA FOR NOV 15. ANY LINGERING
LOCALLY HEAVY PRECIPITATION INCREASES THE RISK OF URBAN FLASH FLOODING AND
MUDSLIDES IN BURN SCAR AREAS ACROSS SOUTHERN CALIFORNIA.
MODERATE RISKS OF HEAVY PRECIPITATION AND SNOW FOR THE FOOTHILLS AND HIGHER
ELEVATIONS OF THE SIERRA NEVADA, RESPECTIVELY, REMAIN IN PLACE FOR NOV 15 AND
16. A SECONDARY SHORTWAVE TROUGH MAY BRING ADDITIONAL HEAVY PRECIPITATION TO
THE SIERRA THROUGH DAY 9 (NOV 16). THE RAW ENSEMBLE GUIDANCE CONTINUES TO
INDICATE ENHANCED PROBABILITIES FOR AT LEAST 12 INCHES OF SNOW AND 2 INCHES OF
PRECIPITATION IN THE DESIGNATED MODERATE RISK AREAS. A BROADER AREA IS
HIGHLIGHTED WITH A SLIGHT RISK OF HEAVY PRECIPITATION FOR MUCH OF THE WEST
COAST OR NOV 15 AND 16 AS WELL. BY DAY 10, PRECIPITATION SIGNALS ARE DIMINISHED
ACROSS THE WEST COAST AND PRECIPITABLE WATER ANOMALIES ARE FORECAST TO BE
REDUCED RELATIVE TO THIS ACTIVE PERIOD.
AS 500-HPA HEIGHTS FALL AND ANOMALOUS MID-LEVEL TROUGHING BECOMES ESTABLISHED
OVER THE WEST, THERE IS LIKELY TO BE A PERIOD OF HEAVY SNOWFALL ACROSS THE
NORTHERN TO CENTRAL ROCKIES AND WASATCH MOUNTAINS OF UTAH LASTING THROUGH THE
18TH. ALTHOUGH MODEL SOLUTIONS DIFFER ON HOW THE 500-HPA LONGWAVE PATTERN
EVOLVES DURING MID-NOVEMBER, THE ECENS AND GEFS AGREE THAT MOUNTAIN SNOWPACK
WILL LIKELY INCREASE PRIOR TO THANKSGIVING. ACCUMULATING SNOW COULD EVEN OCCUR
AT LOWER ELEVATIONS OF THE GREAT BASIN ONCE THE AMPLIFIED TROUGH SHIFTS WELL
INLAND.
A SHORTWAVE TROUGH MAY DIG SOUTHWARD TO THE DESERT SOUTHWEST WHICH WOULD RESULT
IN AN INCREASED CHANCE OF HEAVY PRECIPITATION ACROSS ARIZONA EARLY IN WEEK-2.
ALTHOUGH OVERALL THE MODEL GUIDANCE HAS BACKED OFF ON THE INTENSITY OF THIS
SHORTWAVE TROUGH AND ITS ASSOCIATED PRECIPITATION AMOUNTS, THE ECENS PET STILL
SUPPORTS A SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF ARIZONA, VALID ON
NOVEMBER 15 AND 16. CONSISTENT WITH THE ENHANCED PRECIPITATION SIGNAL, A SLIGHT
RISK OF HEAVY SNOW IS POSTED FOR THE MOGOLLON RIM OF ARIZONA ON THE SAME DAYS.
A DEEPENING LONGWAVE TROUGH OVER THE INTERIOR WEST AND POTENTIAL FOR LEESIDE
SURFACE LOW DEVELOPMENT SUPPORT A SLIGHT RISK OF HIGH WINDS FROM THE ROCKIES
EAST TO THE GREAT PLAINS AND UPPER MISSISSIPPI VALLEY FROM NOVEMBER 15-19. AS
THIS SYSTEM PROGRESSES EASTWARD, PETS AND RAW ENSEMBLE GUIDANCE HAVE INCREASING
SUPPORT FOR HEAVY PRECIPITATION ACROSS PARTS OF THE LOWER MISSISSIPPI,
TENNESSEE, AND OHIO VALLEYS AND SURROUNDING REGIONS DURING THE MIDDLE OF
WEEK-2. THERE REMAINS A GREAT DEAL OF UNCERTAINTY ON THE STRENGTH OF ANY SYSTEM
BUT RETURN FLOW OF THE GULF INTERACTING WITH A FRONTAL SYSTEM WOULD SUPPORT
INCREASED PRECIPITATION AMOUNTS. THEREFORE, A SLIGHT RISK OF HEAVY
PRECIPITATION IS POSTED FOR NOV 17-19.
IN ALASKA, ECENS ENSEMBLE GUIDANCE SUPPORTS A DEEPENING LOW PRESSURE SYSTEM IN
THE BERING SEA EARLY IN WEEK-2 ALONGSIDE A SUBSTANTIAL SURFACE HIGH ACROSS THE
EASTERN PACIFIC, THIS COULD LEAD TO HIGH WINDS ACROSS THE ALEUTIANS AND THE
ALASKA PENINSULA AND BRING ENHANCED PRECIPITATION INTO SOUTHERN ALASKA.
HOWEVER, THE GEFS IS NOT AS SUPPORTIVE OF THIS SOLUTION AND HAZARDOUS
PRECIPITATION THRESHOLDS ARE HIGH FOR THIS REGION. NO ASSOCIATED HAZARD IS
POSTED AT THIS TIME.
FORECASTER: RYAN BOLT
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