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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