367  
FXUS21 KWNC 071751  
PMDTHR  
US HAZARDS OUTLOOK  
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD  
300 PM EDT MAY 07 2025  
 
SYNOPSIS: AN AREA OF MID-LEVEL LOW PRESSURE OVER THE WESTERN CONTIGUOUS U.S.  
(CONUS) AT THE OUTSET OF WEEK-2 IS FAVORED TO SHIFT EASTWARD, LEADING TO  
INCREASED POTENTIAL FOR HEAVY PRECIPITATION AND NEW OR RENEWED LOCALIZED  
FLOODING TO PORTIONS OF THE GREAT PLAINS AND MISSISSIPPI VALLEY, BY THE MIDDLE  
OF THE FORECAST PERIOD. MULTIPLE MODELS DEPICT ENHANCED WINDS AND ANOMALOUSLY  
WARM TEMPERATURES AHEAD OF THIS SYSTEM, THOUGH THRESHOLDS FOR THESE FEATURE  
ARE NOT ANTICIPATED TO REACH HAZARDOUS THRESHOLDS.  
 
HAZARDS  
 
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE CENTRAL AND SOUTHERN  
PLAINS, AND THE MIDDLE MISSISSIPPI VALLEY, FRI-MON, MAY 16-19.  
 
DETAILED SUMMARY  
 
FOR SATURDAY MAY 10 - WEDNESDAY MAY 14:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
FOR THURSDAY MAY 15 - WEDNESDAY MAY 21: ENSEMBLE MEANS FROM THE GEFS, ECENS,  
AND CMCE FOR 500-HPA HEIGHT ANOMALIES DEPICT AN AMPLIFIED TROUGH COMING ASHORE  
OVER THE WEST COAST DURING WEEK-1 AND SPREADING OVER THE WESTERN CONUS BY THE  
OUTSET OF WEEK-2, ALONG WITH VIGOROUS LEE CYCLOGENESIS AND A DEEP SURFACE LOW  
OVER THE GREAT PLAINS. THIS SYNOPTIC SETUP FAVORS MOIST SOUTHERLY FLOW OFF THE  
GULF AND INTO THE GREAT PLAINS AND MISSISSIPPI VALLEY, INCREASING THE POTENTIAL  
FOR HEAVY PRECIPITATION ACROSS A REGION ALREADY IMPACTED BY REPEATED ROUNDS OF  
EXCESSIVE RAINFALL. THE GEFS, ECMWF, AND CMCE PROBABILISTIC EXTREMES TOOLS  
(PETS) FOR HEAVY PRECIPITATION ALL INDICATE AT LEAST A 20% CHANCE OF 3-DAY  
PRECIPITATION TOTALS EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND AT LEAST  
1 INCH FOR MUCH OF THE FORECAST PERIOD ACROSS SOME PORTION OF THE SOUTHERN AND  
CENTRAL PLAINS AND INTO THE MISSISSIPPI VALLEY. THERE IS SOME DISAGREEMENT  
AMONG THE MODELS WITH RESPECT TO THE TIMING, DURATION, AND COVERAGE OF THESE  
CONDITIONS.THE GEFS FAVORS A SLOWER AND SHORTER EVENT WHILE THE ECMWF AND CMCE  
FAVOR A LONGER PERIOD OF HEAVY PRECIPITATION, BEGINNING EARLIER IN THE WEEK-2  
PERIOD. ECMWF UNCALIBRATED PROBABILITIES INDICATE ENHANCED PROBABILITIES OF  
DAILY ACCUMULATED RAINFALL EXCEEDING HALF AN INCH OVER THE REGION FROM MAY  
16-19. A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED FOR PORTIONS OF THE  
CENTRAL AND SOUTHERN PLAINS, AND THE MIDDLE MISSISSIPPI VALLEY FOR THESE DATES,  
COVERING THE DAYS AND AREAS WHERE MODEL AGREEMENT IS STRONGEST. GIVEN COPIOUS  
ANTECEDENT RAINFALL OVER THIS REGION, NEW OR RENEWED RISES IN RIVER AND STREAM  
LEVELS ASSOCIATED WITH THIS PRECIPITATION EVENT ARE POSSIBLE. THERE IS NOT  
ENOUGH CERTAINTY AT THIS TIME TO POST AN ASSOCIATED FLOODING HAZARD BUT THIS  
SITUATION WILL BE CLOSELY MONITORED.  
 
AS THIS SYSTEM EVOLVES, ENHANCED SOUTHERLY FLOW IS ANTICIPATED TO DEVELOP OVER  
THE GREAT PLAINS. THERE ARE INDICATIONS OF THIS FROM THE GEFS AND ECMWF PETS  
WHERE THE FORECAST MAXIMUM WIND SPEED, PARTICULARLY OVER THE SOUTHERN PLAINS,  
INDICATE AT LEAST A 20% CHANCE OF 3-DAY MAXIMUM WIND SPEEDS EXCEEDING THE 85TH  
PERCENTILE THROUGH THE MIDDLE OF THE FORECAST PERIOD. HOWEVER, ABSOLUTE WIND  
SPEEDS DEPICTED IN THESE TOOLS DO NOT REACH HAZARDOUS THRESHOLDS SO NO  
ASSOCIATED HAZARD IS POSTED AT THIS TIME.  
 
POSITIVE 500-HPA HEIGHT DEPARTURES ARE FAVORED OVER MUCH OF THE SOUTHWESTERN  
CONUS DURING THE WEEK-1 PERIOD PRIOR TO THE DEVELOPMENT OF THE PREVIOUSLY  
DISCUSSED AMPLIFIED TROUGH. WHILE THESE POSITIVE HEIGHT ANOMALIES ARE FAVORED  
TO DIMINISH BY WEEK-2, ANOMALOUSLY WARM TEMPERATURES ARE INDICATED BY MULTIPLE  
MODELS ALONG THE LOWER RIO GRANDE VALLEY LATE IN WEEK-1 AND EXTENDING INTO  
EARLY WEEK-2 AS A RESULT OF THIS TRANSIENT UPPER-LEVEL RIDGE. THE PETS FOR  
MAXIMUM TEMPERATURE SHOW A STRONG SIGNAL FOR ANOMALOUS WARMTH IN PERCENTILE  
SPACE, HOWEVER A CLOSE EXAMINATION OF ANTICIPATED MAXIMUM TEMPERATURE VALUES  
BASED ON A RANGE OF MODEL GUIDANCE YIELDS INSUFFICIENT SUPPORT FOR AN  
ASSOCIATED HEAT HAZARD FROM BEING POSTED.  
 
AS SPRING CONTINUES AND DAILY INCOMING SOLAR RADIATION FLUX TOTALS INCREASE,  
ICE-BOUND RIVERS ARE BEGINNING TO BREAK UP IN ALASKA. THERE IS NO ASSOCIATED  
HAZARD POSTED AT THIS TIME BUT THIS SITUATION WILL BE CLOSELY MONITORED IN THE  
COMING DAYS AND WEEKS AS CONDITIONS CAN QUICKLY CHANGE, LEADING TO THE  
POTENTIAL FOR ICE JAMS AND ASSOCIATED FLOODING.  
 
FORECASTER: DANNY BARANDIARAN  
 

 
 
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