302  
FXUS21 KWNC 101831  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT MARCH 10 2025  
 
SYNOPSIS: AN AREA OF REDEVELOPING MID-LEVEL LOW PRESSURE FAVORED OVER THE  
WESTERN CONTIGUOUS U.S. (CONUS) IS EXPECTED TO RENEW THE RISK OF HEAVY  
PRECIPITATION FOR PARTS OF THE SOUTHWEST, AND HIGH ELEVATION SNOWFALL FOR MUCH  
OF THE INTERIOR WEST. WHILE NOT AS POTENTIALLY IMPACTFUL AS A FRONTAL SYSTEM  
FAVORED DURING WEEK-1, ADDITIONAL SURFACE LOW FORMATION IN THE LEE OF ROCKIES  
INCREASES THE RISK FOR HEAVY PRECIPITATION AND LOCALIZED FLOODING OVER PARTS OF  
THE MISSISSIPPI, TENNESSEE AND OHIO VALLEYS, LOWER ELEVATION HEAVY SNOW OVER  
THE NORTHERN TIER OF THE U.S, WITH EPISODE OF HIGH WINDS TO THE EAST OF THE  
FOUR CORNERS. THE COMBINATION OF ELEVATED WINDS, ABOVE-NORMAL TEMPERATURES AND  
VERY DRY CONDITIONS IS EXPECTED TO LEAD TO AN INCREASED WILDFIRE RISK WITH  
RAPID ONSET DROUGHT (ROD) OVER PARTS OF THE SOUTHERN PLAINS. ACROSS ALASKA,  
ENHANCED ONSHORE FLOW SUPPORTS AN INCREASED RISK OF HEAVY PRECIPITATION FOR  
MANY PARTS OF THE SOUTHERN MAINLAND AND THE SOUTHEAST.  
 
HAZARDS  
 
MODERATE RISK OF HIGH WINDS FOR THE CENTRAL AND SOUTHERN HIGH PLAINS, AND  
ROCKIES, TUE-THU, MAR 18-20.  
 
SLIGHT RISK OF HIGH WINDS FOR MANY PORTIONS OF THE CENTRAL AND EASTERN CONUS,  
TUE-FRI, MAR 18-21.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF SOUTHERN CALIFORNIA AND THE  
DESERT SOUTHWEST, TUE, MAR 18.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE OHIO, TENNESSEE, AND  
MISSISSIPPI VALLEY, APPALACHIANS AND THE SOUTHEAST, WED-THU, MAR 19-20.  
 
SLIGHT RISK OF HIGH ELEVATION HEAVY SNOW OVER PORTIONS OF THE GREAT BASIN,  
ROCKIES, CENTRAL AND NORTHERN PLAINS, AND THE UPPER MISSISSIPPI VALLEY,  
TUE-THU, MAR 18-20.  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR SOUTHEAST ALASKA, WED-THU, MAR 19-20.  
 
SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES FOR SOUTHERN TEXAS, TUE, MAR 18.  
 
POSSIBLE FLOODING FOR PARTS OF THE SOUTHERN OHIO, TENNESSEE, AND LOWER  
MISSISSIPPI VALLEYS.  
 
RAPID ONSET DROUGHT RISK ACROSS PORTIONS OF THE SOUTHERN PLAINS.  
 
DETAILED SUMMARY  
 
FOR THURSDAY MARCH 13 - MONDAY MARCH 17:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
FOR TUESDAY MARCH 18 - MONDAY MARCH 24: FOLLOWING A VERY ACTIVE WEATHER PATTERN  
TIED A STRONG FRONTAL SYSTEM DURING WEEK-1, THE GEFS AND ECMWF ENSEMBLES HAVE  
BEEN CONSISTENT IN FAVORING A RELOADING MEAN TROUGH OVER THE WESTERN CONUS,  
WITH THE REBUILDING 500-HPA HEIGHTS DOWNSTREAM EAST OF THE MISSISSIPPI EARLY  
NEXT WEEK. WHILE THE GEFS FAVORS THE MEAN TROUGH AXIS OVER THE GREAT BASIN AT  
THE START OF WEEK-2, THE ECMWF MAINTAINS A MORE WESTERLY SOLUTION OF THIS  
FEATURE, SIGNALING THE PERSISTENCE OF ENHANCED ONSHORE FLOW OVER THE WEST COAST  
WHICH IS REFLECTED IN THE RAW AND CALIBRATED PRECIPITATION TOOLS BETWEEN THE  
MODELS. BASED ON 2-DAY TRENDS IN THE 500-HPA HEIGHT FORECASTS FROM THE GEFS  
WHICH SHOW LOWER HEIGHTS COVERING THE EASTERN PACIFIC AND WEST COAST, DEFERENCE  
IS GIVEN TO THE ECMWF PROBABILISTIC EXTREMES TOOL (PET) WHICH DEPICTS INCREASED  
CHANCES OF 3-DAY AMOUNTS EXCEEDING THE 85TH PERCENTILE AND 1 INCH EARLY IN THE  
PERIOD. THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED OVER SOUTHERN  
CALIFORNIA AND INTO SOUTHERN ARIZONA FOR DAY 8 (MAR 18). BEYOND THIS TIME,  
ANOMALOUS 500-HPA RIDGING IS PREDOMINATELY FAVORED OVER THE EASTERN PACIFIC,  
WHERE MORE NORTHWESTERLY FLOW IS EXPECTED TO BRING A PERIOD OF DRIER CONDITIONS  
FOR THE WEST COAST. ALTHOUGH ANY ADDITIONAL RAINFALL DURING WEEK-2 MAY  
EXACERBATE SATURATED GROUNDS OVER PARTS OF NORTHERN CALIFORNIA AND SOUTHWESTERN  
OREGON ( WHERE SOIL MOISTURE CONTENT CONTINUES TO REGISTER IN THE UPPER  
PERCENTILES), THE FLOODING POSSIBLE HAZARD IS REMOVED FROM THIS PART OF WEST  
COAST AS THE RETURN OF ENHANCED ONSHORE FLOW WOULD BE LIMITED FURTHER NORTH IN  
THE PACIFIC NORTHWEST LATER IN WEEK-2.  
 
WITH MEAN TROUGHING FAVORED TO OVERSPREAD THE INTERIOR WEST, SURFACE LOW  
DEVELOPMENT IS AGAIN FAVORED IN THE LEE OF ROCKIES EARLY IN WEEK-2. FOR THIS  
ITERATION, THE STRENGTH OF THE SHORTWAVE ENERGY AND LEE CYCLOGENESIS DOES NOT  
APPEAR TO BE AS ROBUST AS PREVIOUSLY ADVERTISED WITH THE SURFACE LOW NOW  
FAVORED DURING WEEK-1, HOWEVER THERE IS GOOD SUPPORT IN THE ENSEMBLES DEPICTING  
A FAVORABLE SYNOPTIC SETUP CONSISTING OF A HEAVY PRECIPITATION THREAT RETURNING  
IN THE WARM SECTOR, HIGH WINDS, AS WELL AS ACCUMULATING AND POTENTIALLY HEAVY  
SNOW ON THE BACKSIDE OF THE LOW AS IT TRACKS INTO THE UPPER MIDWEST. A SLIGHT  
RISK OF HEAVY PRECIPITATION ISSUED FROM THE OHIO VALLEY SOUTHWARD TO THE GULF  
FOR DAYS 9 AND 10 (MAR 19-20) WHERE THERE IS AGREEMENT IN THE PETS INDICATING  
AT LEAST A 20% CHANCE FOR 3-DAY AMOUNTS EXCEEDING THE 85TH PERCENTILE AND 1  
INCH. GIVEN THE RETURN OF INCREASED SIGNALS FOR DEWPOINTS EXCEEDING 60 DEG F  
IN ECWMF ENSEMBLE AND DETERMINISTIC SOLUTIONS, THUNDERSTORM ACTIVITY IS ALSO  
POSSIBLE OVER PARTS OF THE MISSISSIPPI AND TENNESSEE VALLEYS. DUE TO THE  
RENEWED PRECIPITATION THREAT WITH ANTECEDENT SATURATED CONDITIONS OVER PORTIONS  
OF THE MISSISSIPPI VALLEY ASSOCIATED WITH ENHANCED PRECIPITATION FAVORED DURING  
WEEK-1 (BASED ON WPC QPF), A POSSIBLE FLOODING HAZARD REMAINS ISSUED OVER A  
BROAD AREA THAT INCLUDES THE SOUTHERN OHIO, TENNESSEE, AND LOWER MISSISSIPPI  
VALLEYS. UPSTREAM, THE RETURN OF ENHANCED TROPOSPHERIC MOISTURE TIED TO THE  
ADVANCING TROUGH ALOFT ALSO SUPPORTS A SLIGHT RISK OF HEAVY SNOW POSTED FOR THE  
HIGHER ELEVATIONS OF THE INTERIOR WEST, AND EXTENDING EASTWARD INTO THE UPPER  
MIDWEST FOR MAR 18-20 BASED ON THE PREDICTED TRACK OF THE MEAN SURFACE LOW.  
WITHIN THE HIGHLIGHTED REGION, THE GEFS BASED SNOW WATER EQUIVALENT (SWE) PET  
INDICATES AT LEAST 20% CHANCES FOR 3-DAY AMOUNTS EXCEEDING THE 85TH PERCENTILE,  
WITH INCREASED CHANCES IN THE RAW ECMWF FOR ACCUMULATIONS UPWARDS OF 4 INCHES  
EARLY IN WEEK-2.  
 
STRENGTHENING SURFACE PRESSURE GRADIENTS ARE AGAIN FEATURED IN THE  
DETERMINISTIC AND ENSEMBLE MEANS ASSOCIATED WITH THE SURFACE LOW. BOTH THE GEFS  
AND ECMWF DEPICT A FAIRLY DEEP TROUGH AXIS EXTENDING INTO SOUTHERN HIGH PLAINS  
AND NORTHERN MEXICO ON DAYS 9 AND 10, WHERE PETS ALSO SHOW THE GREATEST CHANCES  
(30-40%) FOR WIND SPEEDS EXCEEDING THE 85TH PERCENTILE AND 25MPH. GIVEN THIS,  
AND IN CONSIDERATION OF A CONTINUED WILDFIRE RISK WITH DROUGHT CONDITIONS  
REGISTERED (RANGING FROM D0 TO D4), WITH SUPPRESSED PRECIPITATION FAVORED  
DURING WEEK-1 IN THE SOUTHERN HIGH PLAINS, A MODERATE RISK OF HIGH WINDS IS  
POSTED FOR MAR 18-20. A BROADER SLIGHT RISK AREA FOR HIGH WINDS IS POSTED (MAR  
18-21) OVER MUCH OF THE CENTRAL AND EASTERN CONUS BASED ON INCREASED WIND  
SIGNALS IN THE PETS AS THE SURFACE LOW TRACKS NORTHEASTWARD. PRIOR TO THE LOW  
SHIFTING INTO THE MISSISSIPPI VALLEY TO BRING COOLER TEMPERATURES INTO THE  
PLAINS, A SLIGHT RISK OF MUCH ABOVE NORMAL TEMPERATURES IS POSTED OVER SOUTHERN  
TEXAS FOR MAR 18, WHERE THERE IS SUPPORT IN THE PETS FOR TEMPERATURES EXCEEDING  
THE 85TH PERCENTILE AND 90 DEGREES F BY THE OUTSET OF WEEK-2. THE COMBINATION  
OF VERY LITTLE PRECIPITATION, ABOVE-NORMAL TEMPERATURES, AND GUSTY WINDS, ALSO  
SUPPORTS THE CONTINUATION OF A RAPID ONSET DROUGHT (ROD) HAZARD OVER PORTIONS  
OF THE SOUTHERN PLAINS.  
 
OVER ALASKA, ENHANCED ONSHORE FLOW ASSOCIATED WITH AMPLIFIED TROUGHING OVER THE  
BERING STRAIT AND ANOMALOUS RIDGING FAVORED OVER THE GULF OF ALASKA EARLY IN  
WEEK-2 IS EXPECTED TO BRING ABOVE-NORMAL PRECIPITATION FOR MUCH OF THE SOUTHERN  
MAINLAND AND SOUTHEAST. WHILE THE ECMWF IS MORE PRONOUNCED WITH THIS PATTERN  
THAN THE GEFS, BOTH PETS INDICATE 20-40% CHANCES FOR 3-DAY AMOUNTS EXCEEDING  
THE 85TH PERCENTILE OVER, WITH AMOUNTS NEARING HAZARD THRESHOLDS OVER THE  
SOUTHEAST TO SUPPORT THE ADDITION OF A SLIGHT RISK OF HEAVY PRECIPITATION FOR  
MAR 19-20. EPISODES OF HIGH WINDS ARE POSSIBLE WITHIN THE HIGHLIGHTED REGION,  
HOWEVER A CORRESPONDING HAZARD IS NOT ISSUED DUE TO PETS BEING LESS SUPPORTIVE  
OF THIS RISK.  
 
BY DAY 11 (3/21) AND BEYOND, ENSEMBLE GUIDANCE GENERALLY FAVORS A MORE  
DEAMPLIFIED, AND ZONAL PATTERN OVER THE CONUS. ONE EXCEPTION MAY BE THE PACIFIC  
NORTHWEST, WHERE THERE IS MODEST SUPPORT FOR THE POTENTIAL RETURN OF ENHANCED  
ONSHORE FLOW WITH HEAVY PRECIPITATION AND HIGH ELEVATION SNOW OVER THE  
NORTHWESTERN CONUS, THOUGH THERE IS A GOOD AMOUNT OF DISAGREEMENT IN THE  
ENSEMBLES REGARDING THE LOCATION AND EVOLUTION OF A 500-HPA RIDGE NEAR THE WEST  
COAST. ANOTHER NOTABLE ASPECT OF THE EXTENDED RANGE GUIDANCE CONCERNS THE  
SHORTENING OF WAVELENGTHS FEATURED IN SOME OF THE LATEST SOLUTIONS. THIS IS  
TYPICAL OF HEIGHT PATTERNS ENTERING BOREAL SPRING, BUT IT DOES POSE  
PREDICTABILITY CHALLENGES IN TERMS OF HOW WELL MODELS CAN ADJUST, WHICH FURTHER  
ADDS TO FORECAST UNCERTAINTY MOVING FORWARD.  
 
FORECASTER: NICK NOVELLA  
 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.
The Nexlab HPC Page
Main Text Page