009
FXUS21 KWNC 171939
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST FEBRUARY 17 2025
SYNOPSIS: MODEL SOLUTIONS INDICATE A POTENTIAL TRANSITION TO ZONAL FLOW AT
UPPER LEVELS, RESULTING IN A RELATIVELY CALM WEEK-2 FOR THE CONTIGUOUS U.S.
(CONUS) FROM A HAZARDS PERSPECTIVE. LOW PRESSURE OVER THE NORTH PACIFIC AT THE
SURFACE AND MID-LEVELS IS FAVORED TO BRING MOIST ONSHORE FLOW TO THE PACIFIC
NORTHWEST, BRINGING THE POTENTIAL FOR HIGH WINDS, HEAVY PRECIPITATION, AND
HEAVY SNOW TO HIGHER ELEVATIONS FOR PORTIONS OF THE WEEK-2 PERIOD.
HAZARDS
SLIGHT RISK OF HEAVY PRECIPITATION FOR COASTAL PORTIONS OF THE PACIFIC
NORTHWEST, THU-SAT, FEB 27-MAR 1.
SLIGHT RISK OF HEAVY SNOW FOR PORTIONS OF THE CASCADE MOUNTAINS, THU-SAT, FEB
27-MAR 1.
SLIGHT RISK OF HEAVY SNOW FOR PORTIONS OF THE NORTHERN ROCKIES, THU-SAT, FEB
27-MAR 1.
SLIGHT RISK OF HIGH WINDS FOR MUCH OF THE NORTHWESTERN CONUS, TUE-SAT, FEB
25-MAR 1.
DETAILED SUMMARY
FOR THURSDAY FEBRUARY 20 - MONDAY FEBRUARY 24:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY FEBRUARY 25 - MONDAY MARCH 03: MODEL ENSEMBLE SOLUTIONS OF 500-HPA
GEOPOTENTIAL HEIGHTS FROM THE GEFS, ECENS, AND CMCE GENERALLY AGREE ON A
GRADUAL TRANSITION TOWARDS ZONAL FLOW OVER THE CONUS DURING THE WEEK-2 PERIOD,
WITH WEAK POSITIVE HEIGHT ANOMALIES OVER THE WEST COAST AND BROAD BUT WEAK
TROUGHING OVER THE EAST. THIS IS FAVORED TO BRING MILDER TEMPERATURES TO MUCH
OF THE CONUS, BUT DOES LEAD TO THE POTENTIAL FOR HAZARDOUS WEATHER TO PORTIONS
OF THE PACIFIC NORTHWEST WITH ONSHORE FLOW AND ENHANCED MOISTURE TRANSPORT.
MODELS DEPICT A DEEP SURFACE LOW PRESSURE SYSTEM OVER THE NORTH PACIFIC AT THE
OUTSET OF WEEK-2, SETTING UP STRONG ONSHORE FLOW INTO THE COASTS OF OREGON AND
WASHINGTON. THE INTEGRATED VAPOR TRANSPORT (IVT) TOOL INDICATES RELATIVELY WEAK
MOISTURE FLUX INITIALLY, BUT THIS SIGNAL INCREASES DURING DAYS 10-12 WITH
ENHANCED PROBABILITIES OF >250 KG/M/S MOISTURE FLUX NORTH OF 43N. THE GEFS AND
ECMWF PROBABILISTIC EXTREMES TOOLS (PETS) ALSO INDICATE AT LEAST A 20%
PROBABILITY OF 3-DAY PRECIPITATION TOTALS EXCEEDING THE 85TH PERCENTILE AND 2
INCHES NORTH OF CAPE MENDOCINO, THEREFORE A SLIGHT RISK OF HEAVY PRECIPITATION
IS POSTED FOR COASTAL PORTIONS OF OREGON AND WASHINGTON FOR FEB 27-MAR 1. A
SLIGHT RISK OF HEAVY SNOW IS ALSO POSTED FOR FEB 27-MAR 1 FOR THE CASCADE
MOUNTAINS AND PORTIONS OF THE NORTHERN ROCKIES AS THIS MOISTURE MOVES INLAND.
IN ADDITION TO ENHANCED MOISTURE TRANSPORT INTO THE NORTHWESTERN CONUS, MODEL
SOLUTIONS FEATURE TIGHT PRESSURE GRADIENTS OVER THE PACIFIC NORTHWEST, AS WELL
AS IN THE LEE OF THE NORTHERN ROCKIES, WHERE MODEL SOLUTIONS INDICATE THE
POTENTIAL FOR LEE CYCLOGENESIS OVER THE NORTHERN PLAINS DURING THE WEEK-2
PERIOD. THE GEFS AND ECMWF PETS INDICATE AT LEAST A 20% PROBABILITY OF MAXIMUM
WIND SPEED EXCEEDING THE 85TH PERCENTILE AT AT LEAST 25MPH FOR MUCH OF THE
NORTHWESTERN CONUS DURING EARLY AND MIDDLE WEEK-2. THE ECMWF IS ESPECIALLY
BULLISH WITH PROBABILITIES EXCEEDING 40%, BUT THE GEFS HAS A MUCH WEAKER
SIGNAL. A SLIGHT RISK OF HIGH WIND IS POSTED FOR MUCH OF THE NORTHWESTERN CONUS
FOR FEB 25-MAR 1, AND THE POTENTIAL FOR A MODERATE RISK WILL BE REASSESSED
TOMORROW.
DEEP LOW PRESSURE OVER THE NORTH PACIFIC DISCUSSED ABOVE ALSO RESULTS IN MOIST
ONSHORE FLOW FOR SOUTHEASTERN ALASKA, AND THE PETS INDICATE A MODEST POTENTIAL
FOR 3-DAY PRECIPITATION TOTALS TO EXCEED THE 85TH PERCENTILE BUT ACCUMULATION
TOTALS ARE NOT EXPECTED TO EXCEED HAZARDOUS CRITERIA SO NO ASSOCIATED HAZARD IS
POSTED AT THIS TIME. HOWEVER, THERE IS AN INCREASED POTENTIAL FOR LANDSLIDES IN
THE REGION GIVEN COPIOUS ANTECEDENT RAINFALL AND WARMER THAN AVERAGE
TEMPERATURES RESULTING IN HIGHER THAN NORMAL SNOW LINES.
THE ECMWF AND GEFS PETS FOR MINIMUM TEMPERATURE BOTH INDICATE A WEAK SIGNAL FOR
MUCH BELOW NORMAL TEMPERATURES FOR PORTIONS OF THE NORTHEAST U.S. FOR FEB 27-28
BUT TEMPERATURES ARE NOT EXPECTED TO DIP BELOW ADVISORY CRITERIA SO NO
ASSOCIATED HAZARD IS POSTED AT THIS TIME.
FORECASTER: DANNY BARANDIARAN
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