578
FXUS21 KWNC 121819
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 12 2025
SYNOPSIS: AN AREA OF MID-LEVEL HIGH PRESSURE IS FORECAST DURING WEEK-2 OVER THE
WESTERN CONTIGUOUS U.S. (CONUS). THIS IS LIKELY TO BRING ABOVE-NORMAL
TEMPERATURES AND BELOW-NORMAL PRECIPITATION TO MUCH OF THE WEST. HOWEVER, THESE
TEMPERATURES ARE UNLIKELY TO MEET HAZARDOUS CRITERIA. IN THE RIO GRANDE VALLEY,
MID-LEVEL HIGH PRESSURE IS ALSO FAVORED EARLY IN WEEK-2 SUPPORTING INCREASED
RISK OF HAZARDOUS HEAT ACROSS THE REGION. IN THE EAST, AN AREA OF MID-LEVEL
TROUGHING IS FORECAST, WHICH MAY BRING UNSETTLED WEATHER TO PARTS OF THE REGION
BUT NO HAZARDOUS CONDITIONS ARE FORECAST AT THIS TIME.
HAZARDS
SLIGHT RISK OF EXCESSIVE HEAT FOR PORTIONS OF THE RIO GRANDE VALLEY, TUE, MAY
20.
DETAILED SUMMARY
FOR THURSDAY MAY 15 - MONDAY MAY 19:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY MAY 20 - MONDAY MAY 26: IN SOUTHERN TEXAS, ONGOING HEAT AT THE
ONSET OF WEEK-2 REMAINS POSSIBLE. DYNAMICAL MODEL GUIDANCE CONTINUES TO
HIGHLIGHT THE REGION WITH 20-40% CHANCES OF EXCEEDING THE 85TH PERCENTILE AND
100 DEGREES. THE CURRENT WEEK-1 FORECAST FROM THE WEATHER PREDICTION CENTER’S
HEAT RISK GUIDANCE IS HIGHLIGHTING EXTREME HEAT RISK ACROSS PARTS OF THIS
REGION NEXT WEEKEND. SOME OF THE EFFECTS OF THIS HEAT ARE FAVORED TO CONTINUE
INTO EARLY WEEK-2 BEFORE DYNAMICAL MODEL GUIDANCE FAVORS TEMPERATURES FALLING
BELOW 100 DEGREES. THEREFORE, A SLIGHT RISK OF EXCESSIVE HEAT IS FORECAST FOR
PORTIONS OF THE RIO GRANDE VALLEY FOR TUE, MAY 20.
POSITIVE 500-HPA HEIGHT ANOMALIES ARE FORECAST TO BUILD INTO THE WESTERN CONUS
EARLY IN THE WEEK-2 PERIOD. THIS RIDGE IS LIKELY TO BRING ABOVE-NORMAL
TEMPERATURES AND BELOW-NORMAL PRECIPITATION TO PARTS OF THE WEST, PARTICULARLY
THE CENTRAL VALLEY AND DESERT SOUTHWEST. THE PROBABILISTIC EXTREMES TOOL (PET)
FROM THE GEFS IS FORECASTING 40-50% CHANCES OF TEMPERATURES EXCEEDING THE 85TH
PERCENTILE CLIMATOLOGICALLY ACROSS PORTIONS OF CALIFORNIA. THE MAIN THREAT
WOULD BE FOR THE CENTRAL VALLEY AT THIS TIME. HOWEVER, RAW ENSEMBLE MEANS AND
DETERMINISTIC GEFS AND ECMWF SHOW TEMPERATURES REACHING THE LOW TO MID 90’S
ACROSS THE NORTHERN CENTRAL VALLEY AND MID TO UPPER 90’S FURTHER SOUTH. THESE
TEMPERATURES WOULD BE UNLIKELY TO REACH HAZARDOUS CRITERIA BUT COULD BE A SHOCK
TO THE SYSTEM AFTER A RELATIVELY COOLER PATTERN LEADING INTO WEEK-2. IN THE
DESERT SOUTHWEST, TEMPERATURES IN THE LOW 100’S ARE POSSIBLE AND WILL BE
MONITORED IN THE COMING DAYS FOR AN INCREASE IN THE HAZARDOUS HEAT THREAT.
IN THE GREAT PLAINS AN AREA OF MID-LEVEL LOW PRESSURE WITH AN ASSOCIATED
SURFACE LOW IS PREDICTED TO EJECT OUT OF THE ROCKIES AT THE END OF WEEK-1. ON
DAY 8, THE ECENS FAVORS THIS SYSTEM BEING LOCATED OVER THE GREAT PLAINS,
HOWEVER, THE GEFS IS QUITE A BIT FURTHER EAST, WITH A WEAKER SYSTEM. THERE IS
POTENTIAL FOR THIS FEATURE TO BRING A PERIOD OF THUNDERSTORMS TO PARTS OF THE
REGION EARLY IN THE WEEK-2 PERIOD. HOWEVER, THERE IS TOO MUCH UNCERTAINTY AT
THIS TIME TO HIGHLIGHT AN ASSOCIATED HAZARD THREAT THUS NONE ARE POSTED AT THIS
TIME. AS THIS SYSTEM MOVES INTO THE GREAT LAKES THE MID-LEVEL FEATURE IS
FORECAST TO STALL. THIS MAY BRING RELATIVELY UNSETTLED WEATHER TO PARTS OF THE
REGION BUT IT IS DIFFICULT TO PINPOINT ANY HAZARDOUS CONDITIONS AT THIS TIME
PRECLUDING ASSOCIATED HAZARDS FROM BEING DESIGNATED AT THIS TIME.
AS SPRING CONTINUES AND DAILY INCOMING SOLAR RADIATION FLUX TOTALS INCREASE,
ICE-BOUND RIVERS NORTH OF THE ARCTIC CIRCLE 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: RYAN BOLT
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