270
FXUS21 KWNC 151823
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 15 2025
SYNOPSIS: STRONG MID-LEVEL HIGH PRESSURE FORECAST TO OVERSPREAD THE WESTERN
CONTIGUOUS U.S. (CONUS) ELEVATES THE POTENTIAL FOR AN EXCESSIVE HEAT THREAT
EMERGING OVER PARTS OF THE CENTRAL CALIFORNIA VALLEY, DESERT SOUTHWEST, AND
INTERIOR WEST LATE NEXT WEEK, WITH EXCESSIVE HEAT CONDITIONS POSSIBLY LINGERING
FROM WEEK-1 INTO WEEK-2 OVER PARTS OF THE SOUTHERN PLAINS. EAST OF THE
MISSISSIPPI, MID-LEVEL LOW PRESSURE IN THE MODEL GUIDANCE SUPPORTS COOLER THAN
NORMAL SPRINGTIME TEMPERATURES, WITH THE POTENTIAL FOR UNSETTLED WEATHER OVER
PARTS OF THE EASTERN SEABOARD HEADING INTO MEMORIAL DAY WEEKEND.
HAZARDS
MODERATE RISK OF EXCESSIVE HEAT FOR PARTS OF CALIFORNIA AND THE DESERT
SOUTHWEST, FRI-SUN, MAY 23-25.
SLIGHT RISK OF EXCESSIVE HEAT FOR PORTIONS OF TEXAS AND NEW MEXICO, FRI-SAT,
MAY 23-24.
SLIGHT RISK OF EXCESSIVE HEAT FOR PARTS OF CALIFORNIA, THE DESERT SOUTHWEST,
AND INTERIOR WEST FRI-THU, MAY 23-29.
SLIGHT RISK OF EPISODIC HIGH WINDS FOR PARTS OF THE PACIFIC NORTHWEST AND
CALIFORNIA, FRI-TUE, MAY 23-27.
SLIGHT RISK OF PERIODIC HEAVY PRECIPITATION FOR PORTIONS OF THE MID-ATLANTIC,
APPALACHIANS, AND THE NORTHEAST, FRI-SUN, MAY 23-25.
SLIGHT RISK OF EPISODIC HIGH WINDS FOR PORTIONS OF THE MID-ATLANTIC,
APPALACHIANS, AND THE NORTHEAST, FRI-SUN, MAY 23-25.
DETAILED SUMMARY
FOR SUNDAY MAY 18 - THURSDAY MAY 22:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY MAY 23 - THURSDAY MAY 29: SINCE YESTERDAY, THE HAZARDS PERSPECTIVE
CONTINUES TO BE ON TRACK. BASED ON THE LATEST DYNAMICAL MODEL 500-HPA HEIGHT
FORECASTS FROM THE GEFS AND ECMWF EARLY IN WEEK-2 (MAY 23-25), THE FAVORED
WEAKENING OF AN AMPLIFIED SUBTROPICAL RIDGE CENTERED OVER THE GULF OF AMERICA
IS EXPECTED TO LEAD TO A MODERATION OF TEMPERATURES LATE NEXT WEEK AND OFFER
SOME RELIEF TO THE ONGOING EXCESSIVE HEAT CONDITIONS BEING FELT OVER THE
SOUTHERN PLAINS. MEANWHILE, THERE HAS BEEN VERY GOOD CONSISTENCY IN THE MODELS
BRINGING IN STRONG 500-HPA RIDGING FROM THE EASTERN PACIFIC, WITH THE RIDGE
CENTER FAVORED TO SHIFT INTO THE GREAT BASIN AND INTERIOR WEST AND BECOME MORE
STATIONARY BY THE MIDDLE OF WEEK-2. THE LATEST 0Z RUN OF THE ECMWF ENSEMBLE HAS
BECOME MORE PRONOUNCED WITH THE STRENGTH OF THIS MID-LEVEL FEATURE, INCREASING
CONFIDENCE FOR ABOVE-NORMAL TEMPERATURES FOR A BROAD PORTION OF THE WEST, ALONG
WITH EXCESSIVE HEAT CONDITIONS PARTICULARLY FOR THE LOWER ELEVATION AREAS OF
CALIFORNIA AND THE DESERT SOUTHWEST. DOWNSTREAM OF THE RIDGE CENTER IN THE
WEST, ANOMALOUS TROUGHING REMAINS FAVORED MAINLY EAST OF THE MISSISSIPPI, WHERE
A LINGERING AREA OF SURFACE LOW PRESSURE OVER THE MID-ATLANTIC AND NORTHEAST
LOOKS TO BRING A PERIOD OF UNSETTLED WEATHER, WITH THE POTENTIAL FOR GUSTY
WINDS AND LOCALLY HEAVY PRECIPITATION OVER PARTS OF THE EASTERN SEABOARD
HEADING INTO MEMORIAL DAY WEEKEND.
WITH A 500-HPA TROUGH DIVING INTO THE MIDWEST TO HELP SUPPRESS THE SUBTROPICAL
RIDGE AND PROMOTE MORE NORTHWESTERLY FLOW INTO THE SOUTHERN TIER OF THE U.S
LATE NEXT WEEK, THERE IS A CONSIDERABLE REDUCTION IN TEMPERATURES DEPICTED BY
THE RAW AND CALIBRATED TOOLS. THEREFORE, A MODERATE RISK OF EXCESSIVE HEAT IS
DISCONTINUED OVER SOUTHERN TEXAS IN THE UPDATED OUTLOOK. BY DAYS 8 AND 9, THERE
ARE DIFFERENCES BETWEEN THE GEFS AND ECWMF RAW AND CALIBRATED TOOLS, WITH THE
LATTER MAINTAINING A GENERALLY COOLER SOLUTION OVER THE SOUTHERN PLAINS.
DESPITE THIS, WEAK RIDGING ALOFT REMAINS FAVORED RESULTING IN MODEST SUPPORT
FOR DAYTIME TEMPERATURES EXCEEDING THE TRIPLE DIGITS, SUPPORTING THE
CONTINUATION OF A SLIGHT RISK OF EXCESSIVE HEAT FOR NEW MEXICO AND TEXAS, VALID
THROUGH MAY 24. COVERAGE FOR THE SLIGHT RISK AREA IS REMOVED OVER PARTS OF THE
LOWER MISSISSIPPI VALLEY WHERE THERE IS BETTER SUPPORT FOR NEAR TO BELOW NORMAL
TEMPERATURES. IN ADDITION, RAPID ONSET DROUGHT (ROD) IS POSSIBLE OVER
PARTITIONS OF SOUTHEASTERN TEXAS GIVEN THE CONTINUATION OF ABOVE-NORMAL
TEMPERATURES OVER THIS PART OF THE STATE, THOUGH MODEL GUIDANCE IS MIXED IN
TERMS OF WHETHER ANY ENHANCED PRECIPITATION WOULD OCCUR DURING WEEK-2.
THEREFORE, AN ASSOCIATED ROD HAZARD IS NOT DESIGNATED AT THIS TIME BUT THIS
DOES BEAR MONITORING MOVING FORWARD.
ACROSS THE WEST, RAW MODEL TOOLS SHOW INCREASING MAXIMUM TEMPERATURES THAT ARE
QUICK TO RESPOND TO THE MID-LEVEL RIDGING OVERSPREADING THE WEST COAST AND
INTERIOR WEST NEXT WEEK. OVER THE PAST FEW DAYS, BOTH THE GEFS AND ECMWF
PROBABILISTIC EXTREME TOOLS (PETS) HAVE TRENDED MORE ROBUSTLY, SHOWING STRONGER
AND MORE EXPANSIVE ANOMALOUSLY WARM TEMPERATURE SIGNALS IN PERCENTILE SPACE.
DUE TO THE STRONGER RIDGING IN THE ECMWF, THERE IS A HIGHER HEAT POTENTIAL
INDICATED WITH 30-40% CHANCES FOR MAXIMUM TEMPERATURES EXCEEDING THE 90TH
PERCENTILE OVER CALIFORNIA, GREAT BASIN AND THE DESERT SOUTHWEST. DESPITE THE
GEFS SIGNALS REMAINING COMPARATIVELY WEAKER WITH THE HEAT POTENTIAL THAN THE
ECMWF, THESE TOOLS GENERALLY SUPPORT THE CONTINUATION OF A MODERATE RISK OF
EXCESSIVE HEAT FROM THE CENTRAL CALIFORNIA VALLEY INTO THE DESERT SOUTHWEST,
VALID THROUGH MAY 25 BEFORE HEAT THE POTENTIAL BEGINS TO SUBSIDE. WITHIN THE
MODERATE RISK AREA, THERE ARE ELEVATED CHANCES FOR DAYTIME TEMPERATURES
EXCEEDING THE 95 DEGREES F AS FAR NORTH AS SACRAMENTO, CALIFORNIA, AND 105
DEGREES F IN THE LOWER ELEVATIONS OF THE DESERT SOUTHWEST THROUGH THE MIDDLE OF
THE PERIOD. WHILE THESE TEMPERATURES WOULD NOT MEET HAZARDOUS CRITERIA DURING
THE PEAK OF THE SUMMER, SUCH TEMPERATURES MAY REACH ADVISORY OR WARNING LEVELS
BASED ON NWS HEAT RISK CLIMATOLOGY FOR THIS OF THE YEAR. A BROADER SLIGHT RISK
AREA OF EXCESSIVE HEAT IS HIGHLIGHTED FOR THE ENTIRETY OF WEEK-2, COVERING THE
HIGHER ELEVATIONS OF THE GREAT BASIN AND PARTS OF THE ROCKIES WHERE THE PETS
INDICATE AT LEAST A 20% CHANCE OF MAXIMUM TEMPERATURES EXCEEDING 90 DEGREES F.
COUPLED WITH A MORE PERSISTENT MEAN TROUGH DOWNSTREAM OVER THE EAST, ENSEMBLES
SUGGEST A MORE STABLE RIDGE/TROUGH PATTERN DEVELOPING OVER THE CONUS, WHICH
COULD BRING A MORE PROLONGED RISK OF EXCESSIVE HEAT CONDITIONS ACROSS THE WEST
THROUGH THE END OF MAY. THIS POTENTIAL WILL CONTINUE TO BE ASSESSED IN UPCOMING
OUTLOOKS THIS WEEK.
IN ADDITION TO THE HEAT POTENTIAL THROUGHOUT THE WEST, ENHANCED OFFSHORE FLOW
REMAINS FAVORED THIS IS LIKELY TO BRING A PERIOD OF SUPPRESSED PRECIPITATION,
BUT A STRONG MEAN SURFACE PRESSURE GRADIENT FAVORED OVER NORTHERN CALIFORNIA
AND THE PACIFIC NORTHWEST IN THE GEFS AND ECMWF ENSEMBLES, WHICH WOULD BE
FAVORABLE TO EPISODES OF HIGH WINDS. THEREFORE, A SLIGHT RISK OF HIGH WINDS
REMAINS POSTED, AND IS EXTENDED THROUGH MAY 27 BASED ON MORE PERSISTENT SIGNALS
FOR WINDS EXCEEDING THE 85TH PERCENTILE IN THE PETS. ANY ELEVATED WIND SPEEDS
ACROSS THE SOUTHERN HIGH PLAINS AND THE WESTERN CONUS MAY ELEVATE THE RISK FOR
WILDFIRE CONDITIONS GIVEN HIGH ODDS FOR ABOVE-NORMAL TEMPERATURES AND NEAR- TO
BELOW-NORMAL PRECIPITATION FAVORED DURING WEEK-2. SUCH CONDITIONS WOULD LEAD
TO DRIER FUELS, WHERE ANY EPISODES OF DRY THUNDERSTORMS/LIGHTNING COULD
INITIATE WILDFIRE ACTIVITY.
MAINLY EAST OF THE MISSISSIPPI, A MORE COHESIVE 500-HPA TROUGH IS FAVORED IN
THE LATEST ENSEMBLE GUIDANCE, WITH THE MEAN AXIS EXTENDING FROM THE GREAT LAKES
INTO THE SOUTHEAST THAT PERSISTS THROUGH THE MIDDLE OF WEEK-2. AS A RESULT,
MORE NORTHWESTERLY FLOW IS FAVORED TO PROMOTE UNSEASONABLY COOLER TEMPERATURES
FOR MANY PARTS OF THE NORTHEASTERN CONUS, WITH ABOVE-NORMAL PRECIPITATION AND
UNSETTLED WEATHER AHEAD OF THE TROUGH AXIS OVER THE EASTERN SEABOARD. RELATIVE
TO YESTERDAY, ENSEMBLES HAVE COME INTO BETTER AGREEMENT DEPICTING A MEAN
SURFACE LOW CENTERED JUST OFFSHORE OF THE MID-ATLANTIC AND NORTHEAST THAT
SLOWLY TRACKS TO THE NORTHEAST. ALTHOUGH THE PETS HAVE BECOME WEAKER IN
REGARDS TO HEAVY PRECIPITATION POTENTIAL OVER THE EASTERN SEABOARD, THE
STRONGER MEAN LOW FEATURED IN THE GEFS AND ECMWF, AND ACCOMPANYING ENHANCED
ONSHORE FLOW SUPPORTS THE CONTINUATION OF A SLIGHT RISK OF HEAVY PRECIPITATION
AND SLIGHT RISK OF HIGH WINDS, BOTH VALID FOR MAY 23-25. ANY HEAVY OR
PERSISTENT PRECIPITATION, AS WELL AS GUSTY WINDS ALONG THE I-95 CORRIDOR IS
LIKELY TO HAVE ADVERSE IMPACTS FOR MEMORIAL DAY WEEKEND TRAVELERS AND
BEACHGOERS.
NO HAZARDS ARE ISSUED OVER ALASKA. WARMER THAN NORMAL SPRINGTIME TEMPERATURES
ARE FAVORED MAINLY SOUTH OF THE BROOKS RANGE, WITH A SLIGHT TILT TOWARDS
ABOVE-NORMAL PRECIPITATION FOR MUCH OF THE MAINLAND AND SOUTHEAST, BUT NOTHING
APPROACHING HAZARDOUS THRESHOLDS.
FORECASTER: NICK NOVELLA
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