119
FXUS21 KWNC 101812
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 10 2026
SYNOPSIS: FORECAST MID-LEVEL HIGH PRESSURE SHIFTING ACROSS THE CENTRAL AND
EASTERN CONTIGUOUS U.S. (CONUS) RESULTS IN A MORE FAVORABLE PATTERN FOR
UNSEASONABLY WARM SPRINGTIME TEMPERATURES EAST OF THE ROCKIES, WITH POSSIBLE
EXTREME HEAT CONDITIONS FROM THE MIDDLE MISSISSIPPI VALLEY EASTWARD TO THE
MID-ATLANTIC. SURFACE LOW DEVELOPMENT IN THE LEE OF THE ROCKIES SUPPORTS AN
INCREASED RISK OF HEAVY PRECIPITATION ALONG WITH EPISODES OF HIGH WINDS ACROSS
PORTIONS OF THE GREAT PLAINS AND MISSISSIPPI VALLEY. MEANWHILE, DECREASING
MID-LEVEL PRESSURE OVER THE WESTERN CONUS MAY ALSO BRING EPISODES OF HIGH WINDS
ACROSS COASTAL CALIFORNIA AND OREGON EARLY IN WEEK-2.
HAZARDS
SLIGHT RISK OF EXTREME HEAT FOR PORTIONS OF THE MIDDLE AND LOWER MISSISSIPPI,
TENNESSEE AND OHIO VALLEYS, APPALACHIANS, AND MID-ATLANTIC, MON-TUE, MAY 18-19.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE CENTRAL AND SOUTHERN
PLAINS AND THE MIDDLE AND LOWER MISSISSIPPI VALLEY, MON-WED, MAY 18-20.
SLIGHT RISK OF HIGH WINDS FOR MUCH OF COASTAL CALIFORNIA AND OREGON, MON-TUE,
MAY 18-19.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF THE ROCKIES AND THE NORTHERN AND
CENTRAL PLAINS, MON-TUE, MAY 18-19.
DETAILED SUMMARY
FOR WEDNESDAY MAY 13 - SUNDAY MAY 17:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR MONDAY MAY 18 - SUNDAY MAY 24: DYNAMICAL MODELS CONTINUE TO ADVERTISE A
POTENTIALLY SIGNIFICANT PATTERN CHANGE DURING WEEK-2. FOLLOWING A PERIOD
CHARACTERIZED BY PERSISTENT 500-HPA RIDGING OVER MUCH OF THE WESTERN CONUS,
BOTH THE ECMWF AND GEFS ENSEMBLES FAVOR THIS ANOMALOUS RIDGE FEATURE SHIFTING
EASTWARD TOWARDS THE END OF NEXT WEEK, ALLOWING FOR THE DEVELOPMENT OF MORE
TROUGHING UPSTREAM. SUCH A PATTERN TRANSITION IS ANTICIPATED TO REPLACE MUCH OF
BELOW NORMAL SPRINGTIME TEMPERATURES BEING FELT EAST OF THE ROCKIES SINCE EARLY
MAY WITH UNSEASONABLE SPRING WARMTH. DUE TO THE FAVORED AMPLIFICATION OF THE
PATTERN EARLY IN WEEK-2, POSSIBLE EXTREME HEAT CONDITIONS MAY ACCOMPANY THE
MID-LEVEL RIDGE ANOMALY, WHERE THE FAVORED MEAN TROUGHING UPSTREAM ALSO
SUPPORTS THE POTENTIAL FOR SHORTWAVE ACTIVITY AND SURFACE LOW DEVELOPMENT IN
THE LEE OF THE ROCKIES AND INCREASE RISK OF HEAVY PRECIPITATION ACROSS THE
SOUTH-CENTRAL CONUS. EVEN WITH THIS PATTERN CHANGE, HOWEVER, THERE CONTINUES TO
BE VARIATIONS AMONG THE ENSEMBLES IN REGARDS TO THE EVOLUTION AND STRENGTH OF
PATTERN, LEADING TO UNCERTAINTIES IN THE WEEK-2 OUTLOOK.
WITH MUCH OF THE ANOMALOUS RIDGING SHIFTING EASTWARD ACROSS THE MIDWEST LATE IN
WEEK-1, WPC SURFACE TEMPERATURE FORECASTS FOR DAY 7 (MAY 17) SHOW A WIDESPREAD
COVERAGE OF ANOMALOUS WARMTH, WITH SEVERAL LOCATIONS INDICATING POSITIVE
TEMPERATURE DEPARTURES IN THE DOUBLE-DIGITS FROM THE SOUTHERN PLAINS
NORTHEASTWARD INTO THE OHIO VALLEY. THIS ANOMALOUS WARMTH IS FAVORED TO PERSIST
AND MIGRATE EASTWARD, WHERE THE NATIONAL BLEND OF MODELS (NBM) CONTINUES TO
SHOW AN INCREASED NUMBER OF LOCATIONS FROM THE MIDDLE MISSISSIPPI VALLEY TO THE
MID-ATLANTIC WITH DAYTIME TEMPERATURE EXCEEDING 90 DEG F AND NEARING RECORD
BREAKING TERRITORY ON DAYS 8 AND 9 (MAY 18-19). WHILE THESE NBM PREDICTED
TEMPERATURES ARE LIKELY TO TRIGGER HEAT ADVISORIES BASED ON HISTORICAL HEAT
RISK DATA (ABOVE ORANGE AND RED LEVELS), THE POTENTIAL FOR MAXIMUM TEMPERATURES
EXCEEDING 90 DEG F REMAINS MUCH LESS SUPPORTED IN THE RAW AND CALIBRATED GEFS
AND ECMWF TEMPERATURE TOOLS, PARTICULARLY OVER THE MIDDLE MISSISSIPPI,
TENNESSEE AND OHIO VALLEYS. IN ADDITION, THE GEFS REMAINS WEAKER WITH THE
RIDGING COMPARED TO THE ECMWF, WHICH IS WELL REFLECTED IN THE PROBABILISTIC
EXTREME TOOLS (PETS). STILL, BOTH THE GEFS AND ECMWF PETS REMAIN SUPPORTIVE OF
A POTENTIAL EXTREME HEAT RISK WITH 20-40% CHANCES OF MAXIMUM DAYTIME
TEMPERATURES EXCEEDING THE 90TH CLIMATOLOGICAL PERCENTILE, AS THESE WARM
SIGNALS IN PERCENTILE SPACE ARE ALSO COLLOCATED WITH THE NBM. THEREFORE, A
SLIGHT RISK OF EXTREME HEAT REMAINS ISSUED WITH COVERAGE NOW EXTENDING FROM THE
MIDDLE AND LOWER MISSISSIPPI VALLEY TO THE MID-ATLANTIC, VALID FOR MAY 18-19
BEFORE MUCH OF THE RIDGING ALOFT IS FAVORED TO DEAMPLIFY. IF SPRING HEAT IS
REALIZED, SUCH TEMPERATURES MAY ADVERSELY IMPACT UNSUSPECTING POPULATIONS
WITHOUT COOLING OR HYDRATION SYSTEMS IN PLACE, AND THOSE WHO ARE NOT YET
ACCLIMATED TO THIS LEVEL OF WARMTH. TOWARDS THE MIDDLE OF THE PERIOD, ENSEMBLES
POINT TO A POTENTIAL REAMPLIFICATION OF THE MID-LEVEL MEAN RIDGING OVER THE
CENTRAL AND EASTERN U.S. WHICH MAY RENEW AN EXCESSIVE HEAT RISK. HOWEVER, THE
ENSEMBLES ALSO FAVOR CONTINUED MEAN LONGWAVE TROUGHING OVER THE CANADIAN
MARITIMES, WHERE ANY DEEPENING COULD SUPPRESS THE RIDGE AND PROMOTE COOLER
CONDITIONS. THIS PRECLUDES ANY ADDITIONAL TEMPERATURE HAZARDS IN BEING POSTED,
BUT ANY RENEWED HEAT POTENTIAL WILL CONTINUE TO BE MONITORED IN UPCOMING
OUTLOOKS.
ACCOMPANYING THE EASTWARD SHIFTING ANOMALOUS 500-HPA RIDGE CENTER, MEAN SURFACE
HIGH PRESSURE REMAINS FAVORED OVER THE SOUTHEASTERN U.S. AND INTO THE WESTERN
ATLANTIC, WHERE THE PREVAILING LOW-LEVEL SOUTHERLY FLOW ALSO INCREASES THE RISK
OF HEAVY PRECIPITATION DUE TO ENHANCED MOISTURE ADVECTION FROM THE GULF. IN
TERMS OF SYNOPTIC FORCING, BOTH THE ECMWF AND GEFS AGREE IN FAVORING CYCLONIC
FLOW OVER THE DESERT SOUTHWEST, BUT DISAGREE IN REGARDS TO THE STRENGTH AND
LOCATION OF MEAN SURFACE LOW DEVELOPMENT. THE ECMWF ENSEMBLE FEATURES TWO MEAN
LOW CENTERS BY THE OUTSET OF WEEK-2, ONE OVER THE SOUTHERN PLAINS AND THE OTHER
OVER SOUTH-CENTRAL CANADA, WHEREAS THE GEFS APPEARS TO BE HAVING DIFFICULTY
RESOLVING ANY MEAN LOW CENTER, AS IT DEPICTS A FAIRLY LARGE DISPERSION OF LOW
CENTERS IN ITS MEMBERS THROUGHOUT THE ENTIRE GREAT PLAINS. DIFFERENCES BETWEEN
THE ECMWF AND GEFS ARE ALSO MANIFEST IN THEIR RAW PRECIPITATION TOOLS, WITH THE
ECMWF (GEFS) SHOWING A STRONGER (WEAKER) RESPONSE OVER THE PLAINS AND
MISSISSIPPI VALLEY FOR DAYS 8-10 (MAY 18-20) COMPARED TO YESTERDAY. WHILE THE
ECMWF IS MORE SUPPORTIVE OF A MODERATE RISK DESIGNATION FOR HEAVY
PRECIPITATION, CONSIDERATION IS GIVEN TO THE RAW AND CALIBRATED CANADIAN
PRECIPITATION TOOLS WHICH LEAN A BIT CLOSER TO THE GEFS. THEREFORE, A SLIGHT
RISK OF HEAVY PRECIPITATION REMAINS POSTED, AND REMAINS VALID THROUGH MAY 20.
NOTWITHSTANDING THIS RISK, ANY ENHANCED PRECIPITATION WITHIN THE HIGHLIGHTED
REGION IS EXPECTED TO BE BENEFICIAL FOR MANY AREAS IN THE PLAINS AND
MISSISSIPPI VALLEY CURRENTLY REGISTERED IN DROUGHT.
THE MEAN TROUGHING OVER THE WESTERN CONUS, ALONG WITH POTENTIAL FOR SHORTWAVE
ACTIVITY, SUPPORTS THE CONTINUATION OF THE SLIGHT RISKS OF HIGH WINDS (BOTH
VALID THROUGH MAY 19) OVER PORTIONS OF THE WEST COAST AS WELL AS OVER THE
INTERIOR WEST AND HIGH PLAINS, TIED TO SURFACE LOW DEVELOPMENT. BOTH THE GEFS
AND ECMWF PETS CONTINUE TO SHOW AT LEAST 20% CHANCES FOR WIND SPEEDS EXCEEDING
THE 85TH PERCENTILE FROM OREGON SOUTHWARD TO SOUTHERN CALIFORNIA, AND ALTHOUGH
THE GEFS PET LACKS ANY WIND SIGNALS DOWNSTREAM IN PROXIMITY TO SURFACE LOW
DEVELOPMENT, BOTH THE ECMWF PET AND UNCALIBRATED WIND TOOLS ARE MORE SUPPORTIVE
WITH INCREASED CHANCES FOR GUSTS EXCEEDING 34KTS (~40MPH) OVER PARTS OF THE
PLAINS.
IN ALASKA, THE TYPICAL PEAK OF THE RIVER ICE BREAKUP SEASON IS APPROACHING, AND
ICE JAM FLOODING CAN OCCUR THIS TIME OF YEAR WITH LITTLE OR NO NOTICE AS
CONDITIONS ON FROZEN RIVERS CAN CHANGE QUICKLY. PLEASE CHECK WITH THE ALASKA
PACIFIC RIVER FORECAST CENTER FOR THE LATEST CONDITIONS AND ADVISORIES.
FORECASTER: NICK NOVELLA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page