072
FXUS21 KWNC 101918
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 10 2024
SYNOPSIS: AMPLIFIED MID-LEVEL LOW PRESSURE IS PREDICTED TO FORM OVER THE
NORTHEASTERN PACIFIC BY THE BEGINNING OF WEEK-2. THIS PATTERN SUPPORTS MULTIPLE
STORMS FORMING OVER OR NEAR THE WEST COAST, LEADING TO AN INCREASED RISK FOR
PERIODIC HEAVY PRECIPITATION, HIGH ELEVATION SNOW, AND HIGH WINDS ACROSS PARTS
OF THE NORTHWESTERN CONTIGUOUS U.S. (CONUS). A SERIES OF STORMS OVER THE GULF
OF ALASKA COULD BRING HIGH WINDS TO COASTAL PORTIONS OF SOUTH-CENTRAL AND
SOUTHEASTERN ALASKA DURING WEEK-2.
HAZARDS
MODERATE RISK OF EPISODIC HIGH WINDS ACROSS COASTAL PORTIONS OF THE PACIFIC
NORTHWEST AND NORTHERN CALIFORNIA, WED-SUN, DEC 18-22.
SLIGHT RISK OF EPISODIC HIGH WINDS ACROSS PORTIONS OF THE PACIFIC NORTHWEST AND
NORTHERN CALIFORNIA, WED-TUE, DEC 18-24.
SLIGHT RISK OF PERIODIC HEAVY PRECIPITATION ACROSS PARTS OF THE PACIFIC
NORTHWEST AND NORTHERN CALIFORNIA, FRI-TUE, DEC 20-24.
SLIGHT RISK OF PERIODIC HEAVY SNOW FOR HIGH ELEVATION PORTIONS OF THE NORTHERN
GREAT BASIN, NORTHERN ROCKIES, CASCADES, SIERRA NEVADA RANGE, AND KLAMATH
MOUNTAINS, FRI-TUE, DEC 20-24.
SLIGHT RISK OF EPISODIC HIGH WINDS ACROSS PARTS OF THE NORTHERN AND CENTRAL
PLAINS, FRI-TUE, DEC 20-24.
SLIGHT RISK OF EPISODIC HIGH WINDS ACROSS PARTS OF SOUTH-CENTRAL AND
SOUTHEASTERN ALASKA, WED-SUN, DEC 18-22.
DETAILED SUMMARY
FOR FRIDAY DECEMBER 13 - TUESDAY DECEMBER 17:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY DECEMBER 18 - TUESDAY DECEMBER 24: MULTIPLE MODELS INDICATE
AMPLIFIED MID-LEVEL TROUGHING FORMING OVER THE NORTHEASTERN PACIFIC BY THE
ONSET OF WEEK-2, SHIFTING EASTWARD WITH TIME. THE GEFS AND ECENS INTEGRATED
VAPOR TRANSPORT (IVT) TOOLS INDICATE ENHANCED IVT VALUES (250 KG/M/S) FAVORABLE
FOR ENHANCED ONSHORE MOISTURE AND INCREASED ATMOSPHERIC RIVER ACTIVITY BY THE
MIDDLE OF WEEK-2, ALTHOUGH WITH SOME DIFFERENCES IN TIMING. WITH THIS PATTERN
SUPPORTING A SERIES OF STORMS IMPACTING THE WEST COAST, A SLIGHT RISK (20-40%
CHANCE) OF PERIODIC HEAVY PRECIPITATION IS DESIGNATED FOR PARTS OF THE PACIFIC
NORTHWEST AND NORTHERN CALIFORNIA, DEC 20-24, WHERE THE GEFS, ECENS, AND CMCE
PROBABILISTIC EXTREMES TOOLS (PETS) INDICATE AT LEAST A 20% CHANCE OF 3-DAY
ACCUMULATED PRECIPITATION EXCEEDING THE 85TH PERCENTILE CLIMATOLOGICALLY AND 2
INCHES (1 INCH FOR THE CENTRAL VALLEY OF CALIFORNIA). A SLIGHT RISK OF PERIODIC
HEAVY SNOW IS HIGHLIGHTED FOR HIGH ELEVATION PORTIONS OF THE NORTHERN GREAT
BASIN, NORTHERN ROCKIES, CASCADES, SIERRA NEVADA RANGE, AND KLAMATH MOUNTAINS
FOR THE SAME PERIOD. UNCALIBRATED ECENS GUIDANCE INDICATES ELEVATED
PROBABILITIES FOR AT LEAST 6 INCHES OF SNOW ACCUMULATED OVER A 3-DAY PERIOD
ACROSS THESE HEAVY SNOW RISK AREAS.
A MODERATE RISK OF EPISODIC HIGH WINDS IS DESIGNATED FOR COASTAL PORTIONS OF
THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA, DEC 18-22, DUE TO INCREASED
PROBABILITIES IN THE PETS COMPARED TO YESTERDAY. THE ECENS (GEFS AND CMCE)
INDICATE AT LEAST A 40% (30%) CHANCE OF WIND SPEEDS EXCEEDING THE 85TH
PERCENTILE AND 40 MPH IN THE MODERATE RISK AREA. A BROADER AREA IS HIGHLIGHTED
OVER THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA WITH A SLIGHT RISK FOR THE
ENTIRETY OF WEEK-2 WHERE THERE IS AT LEAST A 20% CHANCE OF EXCEEDING THESE
THRESHOLDS (LOWER WIND SPEEDS INLAND). AN INCREASED RISK FOR HEAVY
PRECIPITATION AND HIGH WINDS GENERALLY INCREASES CHANCES FOR FLOODING AND
LANDSLIDES.
A SERIES OF SURFACE LOWS AND ASSOCIATED FRONTS ARE FORECAST TO TRACK ACROSS THE
NORTHERN PLAINS BY THE MIDDLE OF WEEK-2. COMBINED WITH ADJACENT SURFACE HIGH
PRESSURE OVER THE GREAT BASIN, THERE IS INCREASED POTENTIAL FOR TIGHT PRESSURE
GRADIENTS SUPPORTING HIGH WINDS. A SLIGHT RISK OF EPISODIC HIGH WINDS IS POSTED
FOR THE NORTHERN AND CENTRAL PLAINS DEC 20-24, WHERE PETS SHOW AT LEAST A 20%
CHANCE OF WIND SPEEDS EXCEEDING THE 85TH PERCENTILE AND 20 MPH.
THE MID-LEVEL TROUGH IN THE NORTHEAST PACIFIC MAY SUPPORT MULTIPLE STORMS
FORMING OVER THE GULF OF ALASKA. A SLIGHT RISK OF EPISODIC HIGH WINDS IS
MAINTAINED FOR COASTAL PORTIONS OF SOUTH-CENTRAL AND SOUTHEASTERN ALASKA,
WED-SUN, DEC 18-22, WHERE THE PETS INDICATE AT LEAST A 20% CHANCE OF WIND
SPEEDS EXCEEDING THE 85TH PERCENTILE AND 40 MPH. THIS PATTERN IS ALSO LIKELY TO
BRING ENHANCED PRECIPITATION TO THESE AREAS, ALTHOUGH THE PETS DO NOT YET
SUPPORT TOTALS REACHING HAZARD CRITERIA AT THIS TIME.
FORECASTER: MELISSA OU
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