343
FXUS21 KWNC 221915
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST DECEMBER 22 2023
SYNOPSIS: MID-LEVEL LOW PRESSURE OVER THE NORTH PACIFIC IS ANTICIPATED TO PEAK
DURING WEEK-1 AND WEAKEN THROUGHOUT WEEK-2. ASSOCIATED SURFACE LOW FORMATION IS
PREDICTED TO BE CENTERED OVER THE ALEUTIANS, INCREASING CHANCES FOR HIGH WINDS
ACROSS COASTAL PORTIONS OF SOUTH-CENTRAL AND SOUTHEASTERN ALASKA. THIS LOW MAY
POTENTIALLY EXTEND FAR ENOUGH SOUTHWARD TO CAUSE LINGERING HAZARDOUS
PRECIPITATION AND WINDS TO PARTS OF THE WEST COAST AND INTERIOR CALIFORNIA
UNTIL THE MIDDLE OF WEEK-2.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF CALIFORNIA, SAT-WED, DEC 30-JAN
3.
SLIGHT RISK OF HEAVY SNOW FOR THE SIERRA NEVADA, SOUTHERN CASCADES, AND COASTAL
RANGES OF NORTHERN CALIFORNIA, SAT-WED, DEC 30-JAN 3.
SLIGHT RISK OF HIGH WINDS FOR COASTAL CALIFORNIA AND SOUTHWESTERN OREGON,
FRI-TUE, SAT-WED, DEC 30-JAN 3.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES ACROSS PARTS OF GEORGIA AND
FLORIDA, SAT-WED, DEC 30-JAN 3.
SLIGHT RISK OF HIGH WINDS ACROSS COASTAL PORTIONS OF SOUTH-CENTRAL AND
SOUTHEASTERN ALASKA, SAT-MON, DEC 30-JAN 1.
DETAILED SUMMARY
FOR MONDAY DECEMBER 25 - FRIDAY DECEMBER 29:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY DECEMBER 30 - FRIDAY JANUARY 05: THERE IS MORE DISAGREEMENT AMONG
MODELS COMPARED TO YESTERDAY REGARDING THE EVOLUTION OF MID-LEVEL TROUGHING
OVER THE NORTH PACIFIC. THE 0Z GEFS ENSEMBLE MEAN DEPICTS A HIGHER AMPLITUDE
TROUGH OVER THE NORTH PACIFIC EXTENDING FURTHER SOUTH TO THE WEST COAST
COMPARED TO ITS ECMWF AND CANADIAN COUNTERPARTS. THIS TRANSLATES INTO THE
ASSOCIATED GEFS ENSEMBLE MEAN AND TOOLS SHOWING GREATER LIKELIHOOD FOR
HAZARDOUS PRECIPITATION AND WINDS TO PARTS OF THE WEST COAST AND INTERIOR
CALIFORNIA THAN THE OTHER MODELS.
DUE TO GENERALLY WEAKER HEAVY PRECIPITATION SIGNALS ACROSS MODEL GUIDANCE
COMPARED TO YESTERDAY, A MODERATE RISK OF HEAVY PRECIPITATION FOR CALIFORNIA IS
NOT INCLUDED IN TODAY’S OUTLOOK. THE DAILY 0Z ECMWF ENSEMBLE MEANS SHOW
SIGNIFICANTLY LESS SPATIAL COVERAGE OF ENHANCED PRECIPITATION COMPARED TO THE
GEFS AND CANADIAN. A SLIGHT RISK OF HEAVY PRECIPITATION IS MAINTAINED OVER
PARTS OF CALIFORNIA, DEC 30-JAN 3, WHERE MULTIPLE MODEL PETS SHOW AT LEAST A
20% CHANCE OF 3-DAY PRECIPITATION EXCEEDING THE 85TH PERCENTILE AND ONE INCH (>
2 INCHES LOCALLY FOR NORTHERN AND CENTRAL REGIONS). A CORRESPONDING SLIGHT RISK
FOR HEAVY SNOW IS MAINTAINED ACROSS HIGHER ELEVATIONS OF THE SIERRA NEVADA AND
COASTAL RANGES OF NORTHERN CALIFORNIA FOR THE SAME TIME PERIOD. A SLIGHT RISK
OF HIGH WINDS IS POSTED FOR COASTAL CALIFORNIA AND SOUTHWESTERN OREGON,
ALTHOUGH THERE IS GREATER UNCERTAINTY COMPARED TO YESTERDAY DUE TO THE
NOTICEABLE DIFFERENCES IN THE EVOLUTION OF THE STORM CENTERED OVER THE
ALEUTIANS. THE GEFS ENSEMBLE MEAN SYNOPTIC PATTERN WOULD BE THE MOST FAVORABLE
FOR HIGH WINDS ACROSS THE WEST COAST. THE PETS SHOW AT LEAST A 20% CHANCE OF
WIND SPEEDS EXCEEDING THE 85TH PERCENTILE AND 25 MPH (40 MPH FOR COASTAL
SOUTHWESTERN OREGON AND NORTHERN CALIFORNIA) WHERE THE HIGH WIND RISK IS
DESIGNATED.
THERE IS MULTI-MODEL DEPICTION OF AMPLIFIED MID-LEVEL RIDGING OVER WESTERN AND
CENTRAL CANADA DURING WEEK-2, WHICH FAVORS SURFACE HIGH PRESSURE EXTENDING FROM
CANADA INTO THE CENTRAL AND SOUTHEASTERN CONUS. THIS PATTERN FAVORS COLDER THAN
NORMAL TEMPERATURES ACROSS THE SOUTHEASTERN CONUS. A SLIGHT RISK OF MUCH BELOW
NORMAL TEMPERATURES IS POSTED FOR PARTS OF GEORGIA AND FLORIDA WHERE THE PETS
INDICATE AT LEAST A 20% CHANCE OF MINIMUM TEMPERATURES FALLING TO THE LOWEST
15TH PERCENTILE CLIMATOLOGICALLY AND NEAR OR BELOW FREEZING. THIS COULD BE THE
FIRST FROST OR FREEZE OF THE SEASON FOR PARTS OF THE FLORIDA PENINSULA.
A STRONG SURFACE LOW CENTERED OVER THE ALEUTIANS BY THE BEGINNING OF THE PERIOD
SUPPORTS THE CONTINUED SLIGHT RISK FOR HIGH WINDS FOR PORTIONS OF SOUTH-CENTRAL
AND SOUTHEASTERN ALASKA, DEC 30-JAN 1, WHERE THE PETS INDICATE AT LEAST A 20%
CHANCE OF WIND SPEEDS EXCEEDING THE 85TH PERCENTILE AND 40 MPH. HIGH WIND
SPEEDS ARE ALSO POSSIBLE OVER MARITIME AREAS IN THE GULF OF ALASKA. THE
GREATEST CHANCES FOR HEAVIER PRECIPITATION AMOUNTS ARE FOR SOUTH-CENTRAL
ALASKA. HOWEVER, DUE TO THE PETS LIMITING THE 3-DAY PRECIPITATION TOTALS TO
BELOW 3 INCHES, AN ASSOCIATED HEAVY PRECIPITATION HAZARD IS NOT DESIGNATED AT
THIS TIME.
FORECASTER: MELISSA OU
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