039
FXUS21 KWNC 191917
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST FEBRUARY 19 2024
SYNOPSIS: THERE IS GENERALLY POOR AGREEMENT AMONG THE MODELS ACROSS MUCH OF THE
CONTIGUOUS UNITED STATES (CONUS) DURING THE WEEK-2 PERIOD TODAY. DEPENDING ON
ITS EVOLUTION, AN AREA OF MID-LEVEL LOW PRESSURE IN THE GULF OF ALASKA COULD
INTRODUCE A PERIOD OF HEAVY PRECIPITATION, SNOW, AND HIGH WINDS TO PORTIONS OF
THE NORTHWESTERN CONUS. MEANWHILE, IN THE EASTERN CONUS AN AREA OF LOW PRESSURE
IS LIKELY TO DEVELOP AND BRING A PERIOD OF HEAVY PRECIPITATION AND WINDY
CONDITIONS TO THE REGION, HOWEVER THIS SYSTEM IS LIKELY TO BE TOO WARM TO
SUPPORT MUCH RISK FOR HEAVY SNOW. IN ALASKA, ARCTIC HIGH PRESSURE OVER THE
NORTHERN PARTS OF THE STATE MAY HELP TO PROMOTE MUCH BELOW NORMAL TEMPERATURES
ACROSS SOUTHERN MAINLAND ALASKA.
HAZARDS
SLIGHT RISK OF PERIODS OF HEAVY SNOW FOR THE SIERRA NEVADA, KLAMATH, AND
CASCADE MOUNTAINS, TUE-FRI, FEBRUARY 27-MARCH 1.
SLIGHT RISK OF PERIODS OF HEAVY SNOW FOR PARTS OF THE NORTHERN ROCKIES,
TUE-FRI, FEBRUARY 27-MARCH 1.
SLIGHT RISK OF PERIODS OF HEAVY PRECIPITATION FROM CENTRAL CALIFORNIA NORTH
THROUGH THE PACIFIC NORTHWEST, TUE-FRI, FEBRUARY 27-MARCH 1.
SLIGHT RISK OF EPISODIC HIGH WINDS FOR MUCH OF THE WESTERN CONUS. TUE-SAT,
FEBRUARY 27-MARCH 2.
SLIGHT RISK OF HEAVY PRECIPITATION FOR MUCH OF THE EASTERN CONUS, EXCLUDING
PARTS OF THE SOUTHEAST, TUE-THU, FEBRUARY 27-29.
SLIGHT RISK OF EPISODIC HIGH WINDS FOR PORTIONS OF THE EASTERN CONUS, TUE-THU,
FEBRUARY 27-29.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES FOR PARTS OF SOUTHERN ALASKA,
TUE-FRI, FEBRUARY 27-MARCH 1.
SLIGHT RISK FOR PERIODS OF HIGH WINDS FOR SOUTHERN COASTAL PORTIONS OF ALASKA,
TUE-SAT, FEBRUARY 27-MARCH 2
DETAILED SUMMARY
FOR THURSDAY FEBRUARY 22 - MONDAY FEBRUARY 26:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY FEBRUARY 27 - MONDAY MARCH 04: THE DYNAMICAL ENSEMBLE MEANS ARE IN
FAIRLY LARGE DISAGREEMENT TODAY REGARDING THE WEEK-2 500-HPA HEIGHTS ACROSS
MUCH OF THE U.S. THE ECENS MAINTAINS A MORE AMPLIFIED PATTERN ACROSS THE DOMAIN
WITH STRONG NEGATIVE 500-HPA HEIGHTS ACROSS NORTHWESTERN NORTH AMERICA AND
STRONG POSITIVE 500-HPA HEIGHT ANOMALIES OVER THE NORTH PACIFIC AND EASTERN
NORTH AMERICA. HOWEVER, THE GEFS IS MUCH WEAKER WITH NEGATIVE 500-HPA HEIGHT
ANOMALIES IN THE GULF OF ALASKA AND BROAD RIDGING ACROSS MOST OF NORTH-CENTRAL
NORTH AMERICA. THIS LEADS TO A LOW-CONFIDENCE FORECAST, PARTICULARLY ACROSS THE
WEST WHERE THE LARGEST DISCREPANCIES BETWEEN THE GEFS AND ECENS PRECIPITATION
PATTERNS ARE FOUND.
THE ECENS RAW OUTPUT AND PROBABILISTIC EXTREMES TOOL (PET) BRING STRONG CHANCES
FOR HEAVY PRECIPITATION TO PARTS OF THE NORTHWESTERN CONUS. THE STRONGEST
PROBABILITIES (>40%) FOR 3-DAY PRECIPITATION AMOUNTS TO EXCEED THE 85TH
CLIMATOLOGICAL PERCENTILE IN THE PET ARE FOUND ACROSS NORTHERN CALIFORNIA AND
OREGON ACROSS THE SOUTHERN CASCADES AND NORTHERN SIERRA NEVADA. THE CANADIAN
PET IS ALSO SOMEWHAT SUPPORTIVE OF A THREAT FOR HEAVY PRECIPITATION WITH
GREATER THAN 30% CHANCES FOR PRECIPITATION TO EXCEED THE 85TH PERCENTILE ACROSS
A SIMILAR REGION. HOWEVER, THE GEFS IS NOT SUPPORTIVE OF ANY HEAVY
PRECIPITATION WITH NO CHANCES FOR PRECIPITATION TO EVEN EXCEED THE 67TH
PERCENTILE ACROSS THE REGION. NEVERTHELESS, DUE TO THE SUPPORT OF THE ECENS AND
CANADIAN, A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED FOR FEBRUARY 27-MARCH
1 FOR NORTHERN CALIFORNIA NORTH THROUGH THE PACIFIC NORTHWEST. AN ASSOCIATED
SLIGHT RISK OF HEAVY SNOW IS POSTED FOR NORTHERN SIERRA NEVADA, KLAMATH, AND
CASCADE MOUNTAINS FOR THE SAME PERIOD. STRONG CONSIDERATION WAS GIVEN FOR A
MODERATE RISK OF HEAVY SNOW FOR PORTIONS OF OREGON AND NORTHERN CALIFORNIA DUE
TO THE STRONG SIGNAL IN THE ECENS PET AND RAW GUIDANCE. HOWEVER, DUE TO THE
DEARTH OF SUPPORT IN THE GEFS, NO MODERATE RISK IS POSTED TODAY AND WILL BE
RE-EVALUATED TOMORROW. FURTHER INLAND, A SLIGHT RISK OF HEAVY SNOW IS ALSO
POSTED FOR THE CLIMATOLOGICALLY FAVORED REGIONS OF THE NORTHERN ROCKIES SOUTH
THROUGH THE NORTHERN WASATCH RANGE AS MOISTURE MOVES INLAND, FEBRUARY 27-MARCH
1. FINALLY, THERE IS BROAD SUPPORT AMONG THE TOOLS FOR A SLIGHT CHANCE OF HIGH
WINDS FOR MUCH OF THE WESTERN CONUS DURING MUCH OF WEEK-2 AS A MID-LEVEL TROUGH
MOVES INLAND.
IN THE EASTERN CONUS, CONFIDENCE IS FAIRLY HIGH EARLY IN THE PERIOD FOR A
FORECASTED SHORTWAVE TROUGH AND ASSOCIATED SURFACE LOW-PRESSURE TO EJECT OUT OF
THE CENTRAL ROCKIES. THIS FEATURE WOULD BRING CHANCES FOR HEAVY PRECIPITATION
AND HIGH WIND TO MUCH OF THE EASTERN CONUS EARLY IN THE PERIOD. THE ECENS AND
GEFS PETS ARE IN GOOD AGREEMENT FOR A LARGE PORTION OF THE EASTERN CONUS TO
HAVE A GREATER THAN 20% CHANCE OF PRECIPITATION TO EXCEED THE 85TH
CLIMATOLOGICAL PERCENTILE. RAW TOOLS ARE SUPPORTIVE OF PRECIPITATION TOTALS
REACHING NEAR AN INCH ACROSS PORTIONS OF THE REGION. MANY OF THESE AREAS WILL
HAVE RECENTLY EXPERIENCED A COLDER STROM WITH THE POTENTIAL FOR SNOW TO BE ON
THE GROUND LEADING TO INCREASED CHANCES FOR FLOODING. THEREFORE, A SLIGHT RISK
OF HEAVY PRECIPITATION IS FORECAST FOR FEBRUARY 27-29. ASSOCIATED WITH THIS
SYSTEM IS A SLIGHT RISK OF HIGH WINDS FOR LARGELY THE SAME AREA FOR FEBRUARY
27-29 WITH ENSEMBLE GUIDANCE INDICATING SURFACE LOW-PRESSURE MAY FALL BELOW
990MB AND SUPPORT FROM THE GEFS AND ECENS PETS.
IN ALASKA, AN AREA OF ARCTIC HIGH PRESSURE IS FORECAST ACROSS THE NORTHERN
PARTS OF THE STATE AND THE YUKON AND SURFACE LOW-PRESSURE IN THE GULF OF
ALASKA. THIS BRINGS CHANCES OF GAP WINDS TO MUCH OF THE SOUTHERN ALASKA
COASTLINE DURING MUCH OF THE WEEK-2 PERIOD. THE DETERMINISTIC GFS AND ECMWF ARE
IN GOOD AGREEMENT FOR THIS POTENTIAL PARTICULARLY ACROSS THE ALASKA PENINSULA
AND SOUTHWEST MAINLAND ALASKA. A SLIGHT RISK OF HIGH WINDS IS POSTED FOR
FEBRUARY 7-MARCH 2 DUE TO THIS RISK. MEANWHILE, TOOLS ARE ALSO STRONGLY
SUPPORTIVE OF MUCH BELOW NORMAL TEMPERATURES ACROSS MUCH OF SOUTHERN MAINLAND
ALASKA DURING THE PERIOD. STRONG NORTHERLY FLOW IS FAVORED ACROSS THE
MID-LEVELS AND PETS ARE BRINGING AT LEAST A 20% CHANCE OF TEMPERATURES TO FALL
BELOW THE 5TH PERCENTILE ACROSS MUCH OF SOUTHERN MAINLAND ALASKA AND NEGATIVE
TEMPERATURE ANOMALIES TO EXCEED 15 DEGC. THEREFORE, A SLIGHT RISK OF MUCH BELOW
NORMAL TEMPERATURES IS FORECAST FOR FEBRUARY 27-MARCH 1.
FORECASTER: RYAN BOLT
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