195
FXUS21 KWNC 041953
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EST MARCH 04 2025
SYNOPSIS: MODELS ARE IN GOOD AGREEMENT REGARDING A ROBUST AREA OF MID-LEVEL LOW
PRESSURE MOVING INTO THE WESTERN CONTIGUOUS U.S. (CONUS) AT THE OUTSET OF
WEEK-2. THIS SUPPORTS INCREASING CONFIDENCE FOR HEAVY PRECIPITATION AND HIGH
ELEVATION HEAVY SNOW ACROSS THE WEST COAST. AS THIS SYSTEM SHIFTS FURTHER
INLAND, AN AREA OF SURFACE LOW PRESSURE IS FAVORED TO EJECT OUT OF THE ROCKIES
AND COULD POTENTIALLY BE A SIGNIFICANT WEATHER SYSTEM TOWARD MID-MARCH, WITH
HEAVY SNOW ACROSS THE NORTHERN TIER AND ENHANCED RAINFALL OVER THE SOUTHEASTERN
CONUS. THE MID-LEVEL LOW MAY RELOAD ACROSS THE WEST COAST LATER IN WEEK-2
FAVORING ONGOING CHANCES OF HEAVY PRECIPITATION. HIGH WINDS ARE A CONCERN
ACCOMPANYING THESE SYSTEMS, WITH ANOMALOUSLY WARM TEMPERATURES ACROSS SOUTH
TEXAS COMBINED WITH DRY SOILS POTENTIALLY EXACERBATING THE WILDFIRE POTENTIAL.
HAZARDS
HIGH RISK OF HEAVY SNOW ACROSS PORTIONS OF THE SIERRA NEVADA MOUNTAINS, WED,
MAR 12.
MODERATE RISK OF HEAVY SNOW ACROSS PORTIONS OF THE SIERRA NEVADA, KLAMATH, AND
SOUTHERN CASCADE MOUNTAINS, WED-THU, MAR 12-13.
MODERATE RISK OF HEAVY PRECIPITATION ACROSS MUCH OF CALIFORNIA AND SOUTHWESTERN
OREGON, WED-THU, MAR 12-13.
MODERATE RISK OF HIGH WINDS ACROSS MUCH OF THE SOUTHWESTERN CONUS, EXTENDING
INTO THE SOUTHERN AND CENTRAL PLAINS, WED-SAT, MAR 12-15.
SLIGHT RISK OF HEAVY SNOW FOR THE CASCADES, KLAMATH, AND SIERRA NEVADA
MOUNTAINS FOR WED-TUE, MAR 12-18.
SLIGHT RISK OF HEAVY SNOW OVER PORTIONS OF THE GREAT BASIN, INTERMOUNTAIN WEST
AND THE ROCKIES, EXTENDING INTO THE NORTHERN AND CENTRAL PLAINS AND UPPER
MIDWEST, WED-SAT, MAR 12-15.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE WEST COAST, WED-TUE, MAR 12-18.
SLIGHT RISK OF PERIODIC HIGH WINDS FOR MUCH OF THE WESTERN AND CENTRAL CONUS,
EXTENDING EASTWARD INTO THE OHIO AND TENNESSEE VALLEYS, AND THE SOUTHEAST,
WED-TUE, MAR 12-18.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE OHIO, TENNESSEE, MIDDLE
AND LOWER MISSISSIPPI VALLEYS, APPALACHIANS, AND THE SOUTHEAST, WED, FRI-SAT,
MAR 12, 14-15.
SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES ACROSS THE RIO GRANDE VALLEY,
WED-FRI, MAR 12-14.
POSSIBLE FLOODING FOR PARTS OF SOUTHWESTERN OREGON AND NORTHERN CALIFORNIA.
DETAILED SUMMARY
FOR FRIDAY MARCH 07 - TUESDAY MARCH 11:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY MARCH 12 - TUESDAY MARCH 18: A HIGHLY AMPLIFIED SHORTWAVE TROUGH
IS FORECAST TO PROGRESS ACROSS THE CONUS DURING WEEK-2, WITH THIS FEATURE
SERVING AS THE FOCAL POINT FOR A VARIETY OF HAZARDS ACROSS THE COUNTY. ENHANCED
ONSHORE FLOW IS FAVORED ALONG THE WEST COAST AS THE TROUGH MOVES INLAND AT THE
OUTSET OF THE PERIOD. THE ECENS PROBABILISTIC EXTREMES TOOL (PET) DEPICTS VERY
HIGH PROBABILITIES (GREATER THAN 80 PERCENT) FOR 3-DAY PRECIPITATION TO EXCEED
THE 85TH CLIMATOLOGICAL PERCENTILE ACROSS SOUTHERN CALIFORNIA, WITH
PROBABILITIES OF AT LEAST 60 PERCENT FOR PRECIPITATION TOTALS EXCEEDING 1-INCH.
THE GEFS PET IS CONSIDERABLY WEAKER, GENERALLY INDICATING PROBABILITIES OF
30-50 PERCENT FOR 3-DAY PRECIPITATION TOTALS EXCEEDING THE 85TH CLIMATOLOGICAL
PERCENTILE AND 1-INCH. ADDITIONALLY, THE ECENS DEPICTS A MORE SOUTHERLY AND
PROLONGED COMPONENT OF INTEGRATED VAPOR TRANSPORT (IVT) EXTENDING INTO SOUTHERN
CALIFORNIA. AS A RESULT OF THESE ENHANCED SIGNALS, ESPECIALLY IN THE ECENS, THE
MODERATE RISK FOR HEAVY PRECIPITATION IS EXTENDED THROUGH SOUTHERN CALIFORNIA
AND IS VALID THROUGH MAR 13. A FLOODING RISK REMAINS OVER THE MORE SATURATED
AREAS OF SOUTHWESTERN OREGON AND NORTHERN CALIFORNIA. IT IS NOT EXTENDED
SOUTHWARD DUE TO COMPARATIVELY DRIER SOILS ACROSS SOUTHERN CALIFORNIA.
HIGH ELEVATION SNOW IS ALSO LIKELY, WITH A QUICK BURST OF VERY HEAVY SNOW
LIKELY ACROSS THE SIERRA NEVADA MOUNTAINS AS THE TROUGH MOVES ASHORE ON DAY-8
(MAR 12). THERE ARE ENHANCED SIGNALS IN THE 0Z ECENS AND GEFS AS WELL AS THE
CORRESPONDING DETERMINISTIC RUNS FOR 24-HOUR SNOW TOTALS EXCEEDING 1-2 FEET
OVER SOME AREAS. THEREFORE, A HIGH RISK FOR HEAVY SNOW IS DESIGNATED FOR MAR 12
ACROSS THE SIERRA NEVADA MOUNTAINS, WITH A MODERATE RISK FOR HEAVY SNOW
CONTINUING THROUGH MAR 13 AND EXTENDING NORTH TO INCLUDE PORTIONS OF THE
KLAMATH AND SOUTHERN CASCADES. FOLLOWING THE PASSAGE OF THIS FIRST TROUGH,
THERE IS GOOD AGREEMENT IN THE ENSEMBLES FAVORING MEAN TROUGHING RELOADING
ACROSS THE EASTERN PACIFIC WHICH IS FAVORED TO BRING A CONTINUED THREAT OF
WEATHER RELATED HAZARDS FOR THE WEST COAST, PERHAPS FOCUSED A BIT MORE TO THE
NORTH COMPARED TO EARLIER IN THE PERIOD. THIS SUPPORTS THE CONTINUATION OF THE
SLIGHT RISKS FOR HEAVY PRECIPITATION AND HIGH ELEVATION SNOW FOR ALL OF WEEK-2.
DOWNSTREAM, SURFACE LOW PRESSURE MOVING ACROSS THE MISSISSIPPI VALLEY AND GREAT
LAKES AT THE START OF THE PERIOD FAVORS ENHANCED PRECIPITATION CHANCES ACROSS
THE SOUTHEAST, WITH THE 0Z GEFS MORE BULLISH WITH THIS FEATURE COMPARED TO THE
0Z ECENS. AS THE AFOREMENTIONED UPSTREAM TROUGH MOVES FARTHER EAST, ANOTHER
AREA OF SURFACE LOW PRESSURE IS PREDICTED TO EJECT OUT OF THE ROCKIES TOWARD
THE MIDDLE OF WEEK-2, AND THERE IS BETTER AGREEMENT BETWEEN THE 0Z GEFS AND
ECENS THAT THIS MAY BE A MORE SIGNIFICANT WEATHER SYSTEM AROUND MID-MARCH. A
SLIGHT RISK OF HEAVY PRECIPITATION IS ISSUED FOR MAR 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 OVER THE LOWER MISSISSIPPI AND TENNESSEE
VALLEYS AND SOUTHEAST, 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. HEAVY SNOW IS ALSO
POSSIBLE ACROSS THE NORTHERN PERIPHERY OF THIS SYSTEM, WITH THE UNCALIBRATED 0Z
ECENS DEPICTING 20-40 PERCENT CHANCES FOR SNOWFALL TOTALS EXCEEDING 4 INCHES
ACROSS PORTIONS OF THE NORTHERN AND CENTRAL PLAINS AND UPPER MIDWEST SUPPORTING
A SLIGHT RISK OF HEAVY SNOW ACROSS THESE REGIONS AND EXTENDING BACK THROUGH THE
ROCKIES, GREAT BASIN, AND INTERMOUNTAIN REGION MAR 12-15 BASED ON THE GEFS SNOW
WATER EQUIVALENT (SWE) PET.
WITH MULTIPLE WAVES OF MID-LEVEL TROUGHING, AND POTENTIALLY STRONG SURFACE LOWS
TO INDUCE STRENGTHENING PRESSURE GRADIENTS DURING WEEK-2, A BROAD SLIGHT RISK
OF HIGH WINDS IS POSTED AND COVERS MUCH OF THE WESTERN AND CENTRAL 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 12-15) OVER THE SOUTHWESTERN CONUS AND EXTENDING INTO
THE CENTRAL AND SOUTHERN PLAINS BASED ON THE PETS WHICH INDICATE 30-50 PERCENT
CHANCES FOR WIND SPEEDS EXCEEDING THE 85TH PERCENTILE TIED TO AMPLIFIED
TROUGHING SHIFTING EASTWARD WITH TIME. A PERIOD OF ANOMALOUSLY WARM
TEMPERATURES IS POSSIBLE ACROSS THE RIO GRANDE VALLEY EARLY IN WEEK-2, WITH THE
UNCALIBRATED 0Z ECENS SHOWING SOME AREAS WITH MAXIMUM TEMPERATURES EXCEEDING 95
DEG F (CLOSER TO 90 DEG F IN THE GEFS) ALONG WITH INCREASING SIGNALS IN THE
CORRESPONDING PETS. A SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURE IS POSTED
ACROSS THE REGION, MAR 12-14, AND IN COMBINATION WITH THE HIGH WINDS, MAY
INCREASE THE WILDFIRE RISK, 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: THOMAS COLLOW
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