962
FXUS21 KWNC 222058
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST JANUARY 22 2024
SYNOPSIS: THIS COULD BE A VERY STORMY PERIOD IN PORTIONS OF THE WESTERN
CONTIGUOUS U.S., PARTICULARLY ACROSS CALIFORNIA. HEAVY PRECIPITATION AND
HIGHER-ELEVATION HEAVY SNOWFALL ARE STRONGLY INDICATED IN MODEL GUIDANCE FOR
THE FIRST HALF OF WEEK-2, ALONG WITH HIGH WINDS NEAR THE PACIFIC COAST. AS THE
SYSTEM SPREADS EASTWARD, THERE IS AT LEAST A SLIGHT RISK OF HEAVY
PRECIPITATION, HIGH WINDS, AND HEAVY HIGH-ELEVATIONS SNOWFALL FOR SOME AREAS
FROM THE ROCKIES AND SOUTHERN HIGH PLAINS TO THE PACIFIC OCEAN THROUGHOUT
WEEK-2. ELSEWHERE, MUCH BELOW NORMAL TEMPERATURES ARE POSSIBLE OVER PORTIONS OF
MAINLAND ALASKA EARLY IN THE PERIOD, WITH HIGH WINDS POSSIBLE DURING THIS
PERIOD IN SOUTHWESTERN PARTS OF THE STATE. LATER WEEK-2, AS THE STRONG
DISTURBANCE IN THE WEST BEGINS TO MOVE EASTWARD, HEAVY PRECIPITATION IS
POSSIBLE IN PORTIONS OF THE SOUTHEAST.
HAZARDS
HIGH RISK OF HEAVY PRECIPITATION FOR MUCH OF CALIFORNIA AND SOME ADJACENT
LOCATIONS OF NEVADA AND OREGON, TUE-FRI, JAN 30 - FEB 2.
HIGH RISK OF HEAVY SNOW FOR MOST OF THE SIERRA NEVADAS AND THE SOUTHERN
CASCADES, TUE-FRI, JAN 30 - FEB 2.
MODERATE RISK OF HIGH WINDS ALONG MUCH OF THE WEST COAST, TUE-FRI, JAN 30 - FEB
2.
MODERATE RISK OF HEAVY PRECIPITATION FOR CALIFORNIA AND THE WEST COAST,
TUE-SAT, JAN 30 - FEB 3.
MODERATE RISK OF HEAVY SNOW FOR THE SIERRA NEVADAS, SOUTHERN CASCADES, AND THE
NORTHERN COASTAL RANGES OF CALIFORNIA, TUE-SAT, JAN 30 - FEB 3.
SLIGHT RISK OF HEAVY PRECIPITATION FOR MUCH OF THE CONUS FROM THE ROCKIES
WESTWARD, TUE-MON, JAN 30 - FEB 5.
SLIGHT RISK OF HIGH WINDS FOR THE SOUTHERN HIGH PLAINS AND MUCH OF THE CONUS
FROM THE ROCKIES WESTWARD, TUE-MON, JAN 30 - FEB 5.
SLIGHT RISK OF HEAVY SNOW FOR MANY OF THE HIGHER ELEVATIONS ACROSS THE INTERIOR
WEST, TUE-MON, JAN 30 - FEB 5.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR MUCH OF NORTHERN AND WESTERN
MAINLAND ALASKA, TUE-THU, JAN 30 - FEB 1.
SLIGHT RISK OF HIGH WINDS FOR KODIAK ISLAND, SOUTHWESTERN MAINLAND ALASKA, AND
PARTS OF THE ALEUTIANS, TUE-THU, JAN 30 - FEB 1.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHEASTERN CONUS,
SAT-MON, FEB 3-5.
DETAILED SUMMARY
FOR THURSDAY JANUARY 25 - MONDAY JANUARY 29:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY JANUARY 30 - MONDAY FEBRUARY 05: ALMOST ALL GUIDANCE STRONGLY
FAVORS A STORMY PERIOD FOR PORTIONS OF THE CONUS FROM THE ROCKIES WESTWARD,
ESPECIALLY EARLY IN THE PERIOD ALONG THE WEST COAST STATES, WITH THE GREATEST
ODDS FOR HEAVY PRECIPITATION AND HIGH-ELEVATION SNOW ACROSS CALIFORNIA. HIGH
WINDS ARE ALSO SIGNIFICANTLY INDICATED WITH A STRONG SURFACE PRESSURE GRADIENT
FAVORED ALONG MOST OF THE WEST COAST DURING THE FIRST HALF OF WEEK-2.
THERE ARE DIFFERENCES IN THE DETAILS OF TIMING AND EVOLUTION, BUT ALL MODELS
SHOW A STRONG MID-LEVEL TROUGH TRACKING FROM THE CENTRAL NORTH PACIFIC TOWARD
THE WEST COAST DURING WEEK-2, CREATING STRONG LOW-LEVEL FLOW FROM THE PACIFIC
OCEAN INTO THE WESTERN CONUS. THERE IS AN ELEVATED POTENTIAL FOR ATMOSPHERIC
RIVER ACTIVITY AS THIS SET-UP EVOLVES, ESPECIALLY ACROSS CALIFORNIA. THE
PROBABILISTIC EXTREMES TOOL (PET) DERIVED FROM THE EUROPEAN ENSEMBLES HAS THE
MOST ROBUST WET SIGNAL, WITH ODDS EXCEEDING 60 PERCENT FOR PRECIPITATION TOTALS
ABOVE THE 85TH PERCENTILE THROUGHOUT CALIFORNIA DURING THE FIRST THREE DAYS OF
THE PERIOD (JAN 30 - FEB 1). THE PET BASED ON THE CANADIAN ENSEMBLES IS ALSO
ROBUST, SHOWING ODDS FOR SIMILAR PRECIPITATION TOTALS TOPPING 40 PERCENT OVER
MOST OF CALIFORNIA, AND EXCEEDING 60 PERCENT ACROSS THE SOUTHEASTERN HALF OF
THE STATE DURING THE SAME PERIOD. THE EUROPEAN-BASED PET SHOWS AT LEAST A 20
PERCENT CHANCE THAT PRECIPITATION WILL EQUAL OR EXCEED 3 INCHES THROUGH FEB 1
OVER SOME COASTAL AND HIGHER-ELEVATIONS SITES IN NORTHERN AND CENTRAL
CALIFORNIA, AND THE CANADIAN-BASED PET SHOWS SIMILAR RESULTS FARTHER SOUTH IN
THE STATE AS WELL, NEAR LOS ANGELES. THE WET SIGNAL IS NOT AS STRONG IN THE
GEFS PET, AS THAT MODEL SHOWS A SLIGHTLY DIFFERENT EVOLUTION OF MID-LEVEL
FEATURES, BUT STILL COVERS MUCH OF THE FAR WEST WITH ENHANCED ODDS FOR MUCH
ABOVE NORMAL PRECIPITATION. HEAVY PRECIPITATION ACROSS THIS REGION MEANS HEAVY
HIGHER-ELEVATIONS SNOWFALL IS ALSO FAVORED, PARTICULARLY IN THE CENTRAL AND
NORTHERN SIERRA NEVADA AND THE SOUTHERN CASCADES, DURING THE FIRST 3 DAYS OF
WEEK-2. HIGH LIKELIHOODS FOR STRONG WINDS ARE ALSO INDICATED BY THE PET TOOLS,
THOUGH IN THE EUROPEAN ENSEMBLES AND GEFS THE GREATEST ODDS FOR STRONG WINDS
ARE NEAR THE NORTHERN AND CENTRAL WEST COAST, DISPLACED NORTH OF THE STRONGEST
HEAVY PRECIPITATION SIGNALS. BUT SIGNIFICANTLY ENHANCED ODDS FOR HAZARDOUS
WINDS ARE EXTENDED SOUTH FROM THESE AREAS ALONG THE CALIFORNIA COAST AS FAR
SOUTH AS POINT CONCEPTION, BASED ON TOOLS SHOWING STRONG SIGNALS FOR
ATMOSPHERIC RIVER ACTIVITY THERE, WHICH SHOULD CAUSE HIGH WINDS JUST ABOVE THE
SURFACE TO MIX DOWN TO GROUND LEVEL. GIVEN THESE SIGNALS IN THE GUIDANCE, A
MODERATE AND HIGH RISK OF HEAVY PRECIPITATION ARE ISSUED FOR MUCH OF THE WEST
COAST AND VALID THROUGH FEB 2 AND FEB 3, RESPECTIVELY. SIMILARLY, A MODERATE
AND HIGH RISK OF HEAVY SNOW ARE ALSO POSTED OVER THE HIGHER ELEVATIONS OF THE
WEST COAST, ALSO VALID FOR THE SAME PERIODS AS THE HEAVY PRECIPITATION RISKS.
THROUGHOUT WEEK-2, THE AIR ACROSS THE WESTERN CONUS IS EXPECTED TO GET COLDER
WITH TIME, THUS THE HEAVIEST SNOWS ARE EXPECTED TO BE RESTRICTED TO THE HIGHEST
ELEVATIONS EARLY WEEK-2, BUT SNOW ELEVATIONS ARE FORECAST TO LOWER WITH TIME AS
COLDER AIR SLOWLY WORKS ITS WAY INTO THE REGION.
AS WEEK-2 CONTINUES, THE THREAT FOR EXCESSIVE PRECIPITATION IS EXPECTED TO
RECEDE FROM THE NORTHWEST BUT CONTINUE FARTHER SOUTH, EXPANDING INTO THE
ROCKIES AFTER THE MIDDLE OF THE PERIOD. MODELS AND DERIVED PET TOOLS ARE NOT AS
CONSISTENT IN SHOWING HAZARDOUS CONDITIONS EAST OF THE WEST COAST STATES, WITH
THE CANADIAN AND EUROPEAN ENSEMBLE MEANS GIVING THE ADVANCING MID-LEVEL TROUGH
A MORE NEGATIVE TILT LATE IN THE PERIOD, WHICH WOULD MORE SUBSTANTIALLY FAVOR
STORMY WEATHER OVER A BROADER AREA. THE HAZARDOUS SNOW, WIND, AND PRECIPITATION
THREATS AS DEPICTED BY THE PETS ARE NOT AS WIDESPREAD OR ROBUST AS THEY APPEAR
ACROSS THE FAR WEST - ESPECIALLY CALIFORNIA - BUT THESE TOOLS AND THE MID-LEVEL
SET-UP ALL POINT TOWARD SLIGHT RISKS FOR PERIODIC HEAVY PRECIPITATION, HIGH
WINDS, AND HIGH-ELEVATION HEAVY SNOW ACROSS ALL OF THE GREAT BASIN AND ROCKIES
THROUGH THE WEEK-2 PERIOD, WITH THE CORRESPONDING WIND RISK EVENTUALLY
EXPANDING INTO THE SOUTHERN HIGH PLAINS AS WELL.
THE EUROPEAN AND CANADIAN ENSEMBLE MEANS SHOW THE WESTERN CONUS MID-LEVEL
TROUGH EXTENDING EASTWARD LATE WEEK-2, REACHING INTO THE SOUTHEAST TOWARD THE
END OF THE PERIOD. THE TROUGH IS EXPECTED TO TAKE ON A NEGATIVE TILT WHILE
TAPPING GULF OF MEXICO MOISTURE NEAR THE SURFACE, LEADING TO A SLIGHT RISK OF
EXCESSIVE PRECIPITATION IN THE SOUTHEAST (FEB 3-5). THE GEFS HOLDS THE TROUGH
FARTHER WEST, BUT ITS DERIVED PET STILL BRINGS SLIGHTLY INCREASED ODDS FOR
EXCESSIVE PRECIPITATION INTO THE REGION.
WEEK-2 IS FAVORED TO START WITH A STRONG MID-LEVEL TROUGH OVER ALASKA. THIS
FEATURE WEAKENS AS WEEK-2 PROGRESSES, THE TROUGH WILL BE ACCOMPANIED BY MUCH
BELOW NORMAL TEMPERATURES EARLY IN THE PERIOD, CREATING A SLIGHT RISK FOR
EXCESSIVELY COLD CONDITIONS JAN 30 - FEB 1. TEMPERATURES ARE EXPECTED TO
REBOUND AS THE TROUGH WEAKENS, ENDING THE THREAT FOR HAZARDOUSLY COLD
CONDITIONS. MEANWHILE, A PRESSURE GRADIENT BETWEEN LOW SURFACE PRESSURES IN THE
GULF OF ALASKA AND A HIGH PRESSURE SYSTEM FARTHER NORTH OVER THE MAINLAND ARE
EXPECTED TO CREATE STRONG WINDS ACROSS KODIAK ISLAND, THE SOUTHWESTERN
MAINLAND, AND THE ALEUTIANS NORTHEAST OF COLD BAY, SO A SLIGHT RISK OF HIGH
WINDS HAS BEEN POSTED FOR THESE REGIONS. THE THREAT SHOULD EASE AS THE
MID-LEVEL TROUGH WEAKENS AROUND THE MIDDLE OF WEEK-2.
FORECASTER: DANNY BARANDIARAN
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