095
FXUS21 KWNC 281914
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST FEBRUARY 28 2025
SYNOPSIS: AN AREA OF MID-LEVEL LOW PRESSURE MOVING IN FROM THE EASTERN PACIFIC
SUPPORTS INCREASED CHANCES OF HEAVY PRECIPITATION AND HIGH ELEVATION SNOW
ACROSS MUCH OF THE WEST COAST WITH FLOODING POSSIBLE FOR PARTS OF NORTHERN
CALIFORNIA AND SOUTHWESTERN OREGON. AS THE MID-LEVEL PRESSURE SHIFTS EASTWARD
LATER IN WEEK-2, HIGH WINDS AND HEAVY SNOW ARE ALSO POSSIBLE FOR MUCH OF THE
INTERIOR WEST. DOWNSTREAM, MULTIPLE SURFACE LOW PRESSURE SYSTEMS FAVORED
INCREASES THE RISK OF HEAVY PRECIPITATION OVER THE SOUTHEASTERN U.S.
HAZARDS
MODERATE RISK OF HEAVY SNOW FOR PORTIONS OF THE NORTHERN SIERRA NEVADA,
KLAMATH, AND SOUTHERN CASCADE MOUNTAINS, SAT-SUN, MAR 8-9.
MODERATE RISK OF HEAVY PRECIPITATION FOR PORTIONS OF NORTHERN CALIFORNIA AND
SOUTHWESTERN OREGON, SAT-SUN, MAR 8-9.
SLIGHT RISK OF EPISODIC HEAVY SNOW FOR THE CASCADES, KLAMATH, AND SIERRA NEVADA
MOUNTAINS FOR SAT-FRI, MAR 8-14.
SLIGHT RISK OF EPISODIC HEAVY PRECIPITATION FOR PARTS OF WESTERN OREGON,
WESTERN WASHINGTON, AND MUCH OF CALIFORNIA, SAT-FRI, MAR 8-14.
SLIGHT RISK OF EPISODIC HIGH ELEVATION SNOWFALL OVER PORTIONS OF THE GREAT
BASIN, INTERMOUNTAIN WEST AND THE ROCKIES, SAT-FRI, MAR 8-14.
SLIGHT RISK OF PERIODIC HIGH WINDS FOR MUCH OF THE WESTERN CONUS, SAT-FRI, MAR
8-14.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHEAST, SAT, MAR 8.
SLIGHT RISK OF EPISODIC HEAVY PRECIPITATION FOR PORTIONS OF THE OHIO,
TENNESSEE, MIDDLE AND LOWER MISSISSIPPI VALLEYS, AND THE SOUTHEAST, TUE-THU,
MAR 11-13.
POSSIBLE FLOODING FOR PARTS OF SOUTHWESTERN OREGON AND NORTHERN CALIFORNIA.
DETAILED SUMMARY
FOR MONDAY MARCH 03 - FRIDAY MARCH 07:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY MARCH 08 - FRIDAY MARCH 14: THE WEEK-2 HAZARDS PERSPECTIVE LOOKS
TO BE LARGELY ON TRACK BASED ON THE LATEST ENSEMBLE MEAN 500-HPA HEIGHT
FORECASTS FROM THE DYNAMICAL MODELS. LATE NEXT WEEK, SHORTWAVE ENERGY EJECTING
FROM THE ROCKIES LOOKS TO INDUCE DEVELOPMENT OF ANOTHER SURFACE LOW OVER THE
GREAT PLAINS, BRINGING A POTENTIALLY HEAVY PRECIPITATION INTO PARTS OF THE
SOUTHEAST HEADING INTO WEEK-2. DURING THIS TIME UPSTREAM, BOTH THE GEFS AND
ECWMF ARE IN BETTER AGREEMENT RELATIVE TO YESTERDAY IN BUILDING A MID-LEVEL
RIDGE CENTER OVER THE SOUTHWESTERN CONUS, WITH AN AMPLIFYING TROUGH ENCROACHING
THE WEST COAST. THE PATTERN IS CONSISTENT WITH AN ENHANCED ONSHORE FLOW REGIME,
BRINGING AN INCREASED RISK OF HEAVY PRECIPITATION, HIGH WINDS, AND HIGH
ELEVATION SNOW FOR MANY PARTS OF THE WEST EARLY IN WEEK-2. LATER IN THE PERIOD,
ENSEMBLES CONTINUE TO ADVERTISE A PATTERN TRANSITION CONSISTING OF MORE
LONGWAVE TROUGHING BECOMING ESTABLISHED OVER WESTERN NORTH AMERICA, WITH
ANOMALOUS RIDGING BUILDING DOWNSTREAM OVER THE EASTERN U.S. WHILE THIS WOULD
LIKELY PROMOTE A WARMING TREND FOR MUCH OF THE CENTRAL AND EASTERN CONUS, A
TROUGH/RIDGE PATTERN ALSO SUPPORTS A SUSTAINED HIGH WIND AND HIGH ELEVATION
SNOW POTENTIAL ACROSS MUCH OF THE WEST, WITH A RENEWED HEAVY PRECIPITATION RISK
EAST OF THE ROCKIES LATER IN MARCH.
TIED TO THE AFOREMENTIONED SURFACE LOW THAT IS FAVORED TO DEVELOP OVER THE
GREAT PLAINS LATE NEXT WEEK, A SLIGHT RISK OF HEAVY PRECIPITATION REMAINS
POSTED OVER PARTS OF THE SOUTHEAST AND LOWER MID-ATLANTIC FOR DAY 8 (MAR 8).
THERE IS STILL SOME UNCERTAINTY IN REGARDS TO TIMING AND TRACK, HOWEVER THERE
IS BETTER AGREEMENT IN LATEST DETERMINISTIC SOLUTIONS DEPICTING LOCALLY HEAVY
PRECIPITATION, WITH CONTINUED SUPPORT IN THE PROBABILISTIC EXTREMES TOOLS
(PETS) IN THE HIGHLIGHTED REGION BY THE OUTSET OF WEEK-2 BEFORE THE LOW EXITS
THE EASTERN SEABOARD. THESE SOLUTIONS, ALONG WITH THE GEFS BASED SNOW WATER
EQUIVALENT (SWE) PET, ALSO POINT TO ACCUMULATING SNOWFALL AND/OR MIXED
PRECIPITATION ON THE BACKSIDE OF THE LOW FURTHER NORTH, HOWEVER, THERE REMAINS
LESS SUPPORT IN THE ECWMF FOR ANY SNOW ACCUMULATIONS REACHING THRESHOLDS, AND
NO CORRESPONDING HAZARD IS POSTED.
WITH MID-LEVEL TROUGHING FAVORED TO PERSIST OVER THE INTERIOR WEST THROUGHOUT
MUCH OF WEEK-2, ENSEMBLES CONTINUE TO SHOW ADDITIONAL SURFACE LOW FORMATION IN
THE LEE OF THE ROCKIES WITH THE POTENTIAL FOR STRONG RETURN FLOW, ADVECTING
PLENTY OF GULF MOISTURE INTO THE MISSISSIPPI, TENNESSEE, AND OHIO VALLEYS
TOWARDS THE MIDDLE OF THE PERIOD. RELATIVE TO YESTERDAY, MODELS HAVE TAKEN A
MORE NORTHERLY SOLUTION OF THE MEAN LOW, WITH THE GEFS BACKING OFF SOMEWHAT ON
THE DAILY PRECIPITATION TOTALS. STILL, THIS SYNOPTIC SETUP DEPICTED IN THE
GEFS, ECWMF AND CANADIAN ENSEMBLES REMAINS FAVORABLE FOR A RENEWED HEAVY
PRECIPITATION THREAT, AND A SLIGHT RISK OF HEAVY PRECIPITATION REMAINS POSTED
(MAR 11-13) WHERE THE RAW AND CALIBRATED ECWMF GUIDANCE CONTINUES TO SHOW
20-30% CHANCES FOR 3-DAY AMOUNTS EXCEEDING AN 1 INCH. IT IS WORTH NOTING THAT
RAINFALL SURPLUSES REGISTERED IN PARTS OF THE OHIO, TENNESSEE, AND MISSISSIPPI
VALLEYS, AS WELL AS POTENTIALLY HEAVY PRECIPITATION FORECAST IN WEEK-1 (BASED
ON WPC QPF), MAY TRIGGER LOCALIZED FLOODING IN THE HIGHLIGHTED REGION.
UPSTREAM, THERE CONTINUES TO BE GOOD AGREEMENT AMONG THE MODELS DEPICTING
INCREASED AND POSSIBLY HEAVY PRECIPITATION AMOUNTS OVER THE WEST COAST. A
NOTABLE CHANGE EVIDENT IN BOTH THE GEFS AND ECMWF PETS IS THE PERSISTENCE OF
WET SIGNALS AT THE 85TH PERCENTILE LEVEL OVER THE WEST COAST THROUGH MID-MARCH
LIKELY TIED TO THE ANOMALOUS TROUGHING NOW PREDOMINATELY FAVORED OVER THE WEST
THROUGH WEEK-2. THEREFORE, THE SLIGHT RISK OF HEAVY PRECIPITATION, AND THE
ACCOMPANYING SLIGHT RISK OF HIGH ELEVATION HEAVY SNOW REMAINS ISSUED AND ARE
NOW VALID FOR THE ENTIRETY OF WEEK-2. BASED ON THE INTEGRATED VAPOR TRANSPORT
(IVT) TOOLS, AND PETS SHOWING INCREASED CHANCES FOR PRECIPITATION AMOUNTS
EXCEEDING 1.5 TO 2 INCHES OVER NORTHERN CALIFORNIA AND SOUTHWESTERN OREGON
EARLY IN THE PERIOD, A MODERATE RISK OF HEAVY PRECIPITATION AND HIGH ELEVATION
SNOW REMAINS ISSUED FOR THIS PART OF THE WEST COAST FOR MAR 8-9. DUE TO SOIL
MOISTURE CONTENT REGISTERING IN THE UPPER PERCENTILES, AND POSSIBLY HEAVY
PRECIPITATION FAVORED DURING WEEK-1, A POSSIBLE FLOODING HAZARD REMAINS
DESIGNATED ACROSS THE LOWER ELEVATIONS OF NORTHERN CALIFORNIA AND SOUTHWESTERN
OREGON.
BY DAYS 10 AND 11, THE MEAN TROUGH AXIS REMAINS FAVORED TO SHIFT INLAND, WHICH
IS LIKELY TO LEAD TO A REDUCTION OF PRECIPITATION, THOUGH THE GEFS IS HINTING
AT THE POTENTIAL FOR ADDITIONAL SHORTWAVE ENERGY TO RENEW THE HEAVY
PRECIPITATION RISK LATER IN WEEK-2. THIS IS MUCH LESS CLEAR IN THE ECWMF
GUIDANCE, AND IVT TOOLS REMAIN UNSUPPORTIVE OF ANY CHANGES TO THE MODERATE
PRECIPITATION OR SNOW RISK DESIGNATIONS AT THIS TIME, BUT THIS POTENTIAL WILL
CONTINUE TO BE MONITORED IN UPCOMING OUTLOOKS.
WITH ENHANCED ONSHORE FLOW ESTABLISHED 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 SWE VALUES
EXCEEDING THE 85TH PERCENTILE FOR ALL OF WEEK-2. WITH THE AXIS OF THE MEAN
TROUGHING SHIFTING EASTWARD, A SLIGHT RISK OF EPISODIC HIGH WINDS IS ALSO
POSTED FOR MAR 8-14 OVER MUCH OF THE WESTERN CONUS WHERE THERE IS ALSO
CONTINUED SUPPORT IN BOTH THE PETS DEPICTING 20-30% CHANCES FOR WIND SPEEDS
EXCEEDING THE 85TH PERCENTILE.
OVER ALASKA, THE ENHANCED ONSHORE FLOW REGIME ALSO LOOKS TO EXTEND OVER THE
GULF OF ALASKA TO BRING ABOVE-NORMAL TEMPERATURES AND PRECIPITATION FOR MOST OF
WEEK-2. ALTHOUGH PETS SHOW INCREASED CHANCES FOR BOTH PRECIPITATION TOTALS AND
WINDS EXCEEDING THE 85TH PERCENTILE, THERE IS NOT ENOUGH CONFIDENCE ACTUAL
AMOUNTS WILL EXCEED HAZARD THRESHOLDS, AND NO HAZARDS ARE POSTED.
FORECASTER: NICK NOVELLA
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