830
FXUS21 KWNC 031957
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST MARCH 03 2025
SYNOPSIS: ONE OR MORE AREAS OF MID-LEVEL LOW PRESSURE MOVING IN FROM THE
EASTERN PACIFIC SUPPORTS INCREASED CHANCES OF HEAVY PRECIPITATION, EPISODES OF
HIGH WINDS, AND HIGH ELEVATION SNOW ACROSS MUCH OF THE WEST COAST WITH FLOODING
POSSIBLE FOR PARTS OF NORTHERN CALIFORNIA AND SOUTHWESTERN OREGON. WITH
MID-LEVEL LOW PRESSURE SHIFTING EASTWARD, HIGH WINDS AND HEAVY SNOW ARE ALSO
POSSIBLE FOR THE INTERIOR WEST, WITH SURFACE LOW DEVELOPMENT IN THE LEE OF THE
ROCKIES BRINGING INCREASED CHANCES FOR HEAVY PRECIPITATION AND HIGH WINDS INTO
THE SOUTHEASTERN U.S.
HAZARDS
MODERATE RISK OF HEAVY SNOW FOR PORTIONS OF THE NORTHERN SIERRA NEVADA,
KLAMATH, AND SOUTHERN CASCADE MOUNTAINS, WED, MAR 12 .
MODERATE RISK OF HEAVY PRECIPITATION FOR PORTIONS OF NORTHERN CALIFORNIA AND
SOUTHWESTERN OREGON, WED, MAR 12.
MODERATE RISK OF HIGH WINDS FOR MUCH OF THE SOUTHWESTERN CONUS, EXTENDING INTO
THE SOUTHERN AND CENTRAL HIGH PLAINS, TUE-FRI, MAR 11-14.
SLIGHT RISK OF EPISODIC HEAVY SNOW FOR THE CASCADES, KLAMATH, AND SIERRA NEVADA
MOUNTAINS FOR TUE-MON, MAR 11-17.
SLIGHT RISK OF EPISODIC HEAVY PRECIPITATION FOR THE WEST COAST, TUE-MON, MAR
11-17.
SLIGHT RISK OF PERIODIC HIGH WINDS FOR MUCH OF THE WESTERN CONUS, EXTENDED
EASTWARD INTO THE OHIO AND TENNESSEE VALLEYS, AND THE SOUTHEAST, TUE-MON, MAR
11-17.
SLIGHT RISK OF HIGH ELEVATION SNOWFALL OVER PORTIONS OF THE GREAT BASIN,
INTERMOUNTAIN WEST AND THE ROCKIES, TUE-MON, MAR 11-17.
SLIGHT RISK OF EPISODIC HEAVY PRECIPITATION FOR PORTIONS OF THE OHIO,
TENNESSEE, MIDDLE AND LOWER MISSISSIPPI VALLEYS, APPALACHIANS, AND THE
SOUTHEAST, TUE-WED, FRI-SAT, MAR 11-12, 14-15.
POSSIBLE FLOODING FOR PARTS OF SOUTHWESTERN OREGON AND NORTHERN CALIFORNIA.
DETAILED SUMMARY
FOR THURSDAY MARCH 06 - MONDAY MARCH 10:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY MARCH 11 - MONDAY MARCH 17: HEADING INTO EARLY NEXT WEEK, 500-HPA
MEAN HEIGHT FORECASTS FROM THE DYNAMICAL MODELS PREDOMINATELY FAVOR STRONG
TROUGHING SHIFTING INTO THE INTERIOR WEST FROM THE EASTERN PACIFIC, WITH
POSITIVE HEIGHT DEPARTURES OVERSPREADING MUCH OF THE EASTERN U.S. THE FAIRLY
RAPID PROGRESSION OF THIS FORMER MID-LEVEL FEATURE LOOKS TO BRING A PERIOD OF
ENHANCED ONSHORE FLOW FOR MANY PARTS OF THE WEST COAST LATE IN WEEK-1, AS WELL
AS SPAWN A STRONG SURFACE LOW IN THE LEE OF THE ROCKIES BY THE OUTSET OF THE
PERIOD. AS THIS SURFACE SYSTEM AND ITS ASSOCIATED SHORTWAVE MID-LEVEL ENERGY
EJECTS EASTWARD EARLY IN THE PERIOD, THERE IS GOOD AGREEMENT IN THE ENSEMBLES
FAVORING MEAN TROUGHING REDEVELOPING ACROSS THE EASTERN PACIFIC WHICH IS
EXPECTED TO BRING A RENEWED THREAT OF WEATHER RELATED HAZARDS FOR THE WEST
COAST, AS WELL AS EAST OF THE ROCKIES THROUGH THE MIDDLE OF WEEK-2.
EAST OF THE ROCKIES, THERE HAS BEEN GOOD CONSISTENCY IN THE GEFS AND ECWMF
ENSEMBLES FAVORING A STRONG MEAN SURFACE LOW TRACKING INTO THE UPPER MIDWEST
EARLY NEXT WEEK. BY COMPARISON, THE ECWMF IS LESS PRONOUNCED WITH THE SHORTWAVE
TROUGH AXIS THAN THE GEFS, RESULTING IN LESSER PRECIPITATION AMOUNTS IN THE
WARM SECTOR. HOWEVER, BASED ON THE SYNOPTIC SETUP FAVORED WITH AMPLE RETURN
FLOW FROM THE GULF, AND SUPPORT IN THE PROBABILISTIC EXTREMES TOOLS (PETS), THE
POTENTIAL EXISTS FOR HEAVY PRECIPITATION ACROSS PORTIONS OF THE MISSISSIPPI,
TENNESSEE, AND OHIO AND VALLEYS EARLY IN WEEK-2. LATER IN WEEK-2, ADDITIONAL
SURFACE LOW DEVELOPMENT IS FAVORED IN THE LEE OF THE ROCKIES TIED TO A
RELOADING 500-HPA TROUGH OVER THE WESTERN CONUS. CONTRARY TO EARLIER IN THE
PERIOD, THE ECWMF IS COMPARABLY STRONGER THAN THE GEFS WITH THIS SECONDARY MEAN
LOW, THOUGH THERE IS GOOD MULIT-MODEL AGREEMENT DEPICTING RENEWED SOUTHERLY
FLOW FROM THE GULF WITH INCREASED PRECIPITATION AMOUNTS IN THE RAW GUIDANCE.
THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION IS ISSUED FOR MAR 11-12, AS
WELL AS MAR 14-15 TO CAPTURE BOTH OF THESE POTENTIAL EVENTS FROM THE OHIO
VALLEY TO THE GULF COAST. WITHIN THE HIGHLIGHTED REGION, THERE IS INCREASED
SUPPORT FOR DEWPOINT TEMPERATURES EXCEEDING 60 DEGREES F IN THE GULF STATES
WHERE THUNDERSTORM ACTIVITY IS POSSIBLE DURING WEEK-2. DUE TO THE INCREASED
PRECIPITATION RISK OCCURRING OVER MULTIPLE PERIODS, ANTECEDENT SATURATED
CONDITIONS OVER PORTIONS OF THE MISSISSIPPI VALLEY WITH ENHANCED PRECIPITATION
FAVORED DURING WEEK-1 (BASED ON WPC QPF), LOCALIZED FLOODING IS ALSO POSSIBLE
WITHIN THE HIGHLIGHTED REGION.
OVER THE WESTERN CONUS, MUCH OF THE ANOMALOUS 500-HPA TROUGHING IS FAVORED TO
BE OVER THE INTERIOR WEST, SIGNALING A BREAK TO THE ENHANCED ONSHORE FLOW OVER
THE WEST COAST LEADING INTO WEEK-2. HOWEVER, MODELS HAVE BEEN CONSISTENT IN
REDEVELOPING THE MEAN TROUGHING, WITH THE ECMWF FAVORING A STRONGER AND DEEPER
TROUGH AXIS THAN THE GEFS THAT ENCROACHES THE WEST COAST ON DAYS 9 AND 10 (MAR
12-13). THIS IS REFLECTED IN BOTH THE RAW PRECIPITATION AMOUNTS AND THE
INTEGRATED VAPOR TRANSPORT (IVT) TOOLS DEPICTING A MORE SOUTHERLY AND PROLONGED
SOLUTION OF THE HEAVY PRECIPITATION RISK THAN THE GEFS. DIFFERENCES IN THE
LOCATION AND TIMING OF THE HEAVY PRECIPITATION SIGNALS IN THE TOOLS REDUCES
SOME CONFIDENCE IN THE OUTLOOK. HOWEVER, THERE IS SUPPORT FOR A MODERATE RISK
OF HEAVY PRECIPITATION AND AN ACCOMPANYING MODERATE RISK FOR HIGH ELEVATION
SNOW OVER PARTS OF CENTRAL WEST COAST FOR MAR 12 WHERE PETS SHOW UPWARDS OF
30-40% CHANCES FOR AMOUNTS EXCEEDING THE 85TH PERCENTILE AND 2 INCHES. A
BROADER SLIGHT RISK OF HEAVY PRECIPITATION AND HIGH ELEVATION HEAVY SNOW IS
ALSO POSTED FOR THE ENTIRE WEST COAST AND FOR ALL OF WEEK-2 TO CAPTURE THE
ECWMF WET SIGNALS REACHING INTO SOUTHERN CALIFORNIA, AS WELL AS ANY ADDITIONAL
SHORTWAVE ENERGY PROPAGATING ALONG THE LONGWAVE TROUGH AXIS OVER THE WEST LATER
IN MARCH. WITH ENHANCED ONSHORE FLOW REESTABLISHED AND THE TRANSPORT OF
MID-TROPOSPHERIC MOISTURE FAVORED OVER THE INTERIOR WEST, A SLIGHT RISK OF HIGH
ELEVATION HEAVY SNOW REMAINS POSTED FOR MANY PARTS OF THE GREAT BASIN,
INTERMOUNTAIN WEST AND THE ROCKIES WHERE THERE IS CONTINUED SUPPORT IN THE SWE
PET FOR VALUES EXCEEDING THE 85TH PERCENTILE FOR ALL OF WEEK-2.
WITH MULTIPLE WAVES OF MID-LEVEL TROUGHING, AND POTENTIALLY STRONG SURFACE LOWS
TO INDUCE STRENGTHENING PRESSURE GRADIENTS DURING WEEK-2, A SLIGHT RISK OF HIGH
WINDS IS POSTED AND COVERS MUCH OF THE WESTERN CONUS AND EXTENDING EASTWARD
INTO THE OHIO AND TENNESSEE VALLEYS, AND THE SOUTHEAST, VALID FOR ALL OF
WEEK-2. EMBEDDED WITHIN THIS AREA, A MODERATE RISK OF HIGH WINDS IS ALSO POSTED
(MAR 11-13) OVER THE SOUTHWESTERN CONUS AND EXTENDING INTO THE HIGH PLAINS
BASED ON THE IMPROVED ATMOSPHERIC RIVER (AR) SIGNATURE IN THE IVTS, AND THE
PETS WHICH INDICATE 30-50% CHANCES FOR WIND SPEEDS EXCEEDING THE 85TH
PERCENTILE TIED TO AMPLIFIED TROUGHING SHIFTING EASTWARD WITH TIME. IT IS WORTH
NOTING THAT EPISODES OF HIGH WINDS MAY INCREASE THE WILDFIRE RISK OVER THE
CENTRAL AND SOUTHERN HIGH PLAINS, WHERE BELOW-NORMAL PRECIPITATION IS
PREDOMINATELY FAVORED AND DROUGHT CONDITIONS RANGING FROM D0 TO D4 ARE BEING
REGISTERED.
NO HAZARDS ARE POSTED OVER ALASKA. BELOW-NORMAL TEMPERATURES ARE GENERALLY
FAVORED FOR MUCH OF THE MAINLAND WITH NEAR TO ABOVE-NORMAL PRECIPITATION
FORECAST ACROSS THE SOUTHERN MAINLAND AND THE SOUTHEAST.
FORECASTER: NICK NOVELLA
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