861
FXUS21 KWNC 031759
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 03 2026
SYNOPSIS: MID-LEVEL HIGH PRESSURE IS FORECAST ACROSS THE WESTERN CONTIGUOUS
U.S. (CONUS) LEADING TO ABOVE-NORMAL TEMPERATURES AND EXTREME HEAT CONCERNS
EMERGING ACROSS PORTIONS OF THE SOUTHWEST INTO THE CALIFORNIA CENTRAL VALLEY.
CONVERSELY, PERSISTENT MID-LEVEL LOW PRESSURE ACROSS THE GREAT LAKES AND
NORTHEAST FAVORS ANOMALOUSLY COOL WEATHER ACROSS THE REGION, ESPECIALLY EARLY
IN THE PERIOD. THERE REMAINS THE POTENTIAL FOR LATE SEASON FROSTS OVER THE MORE
NORTHERN AND HIGHER ELEVATION AREAS. A FRONTAL SYSTEM AHEAD OF THE MID-LEVEL
LOW MAY BRING ENHANCED PRECIPITATION ACROSS THE GULF COAST EXTENDING INTO THE
EASTERN U.S.
HAZARDS
MODERATE RISK OF EXTREME HEAT ACROSS PORTIONS OF THE DESERT SOUTHWEST AND THE
SOUTHERN CALIFORNIA CENTRAL VALLEY, MON-WED, MAY 11-13.
SLIGHT RISK OF EXTREME HEAT ACROSS PORTIONS OF THE SOUTHWESTERN CONUS AND THE
CALIFORNIA CENTRAL VALLEY, MON-FRI, MAY 11-15.
SLIGHT RISK OF EXTREME HEAT ACROSS CENTRAL AND SOUTHERN FLORIDA, MON-TUE, MAY
11-12.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE GREAT
LAKES, OHIO VALLEY, APPALACHIANS, AND NORTHEAST, MON-TUE, MAY 11-12.
SLIGHT RISK OF HEAVY PRECIPITATION EXTENDING FROM THE NORTHERN GULF COAST
STATES THROUGH THE MID-ATLANTIC AND NORTHEAST, MON-WED, MAY 11-13.
DETAILED SUMMARY
FOR WEDNESDAY MAY 06 - SUNDAY MAY 10:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR MONDAY MAY 11 - SUNDAY MAY 17: THE 0Z ECMWF, GEFS, AND CANADIAN ENSEMBLES
DEPICT A STRONG MID-LEVEL RIDGE (+120 METER POSITIVE HEIGHT ANOMALY) OVER THE
WESTERN CONUS AT THE OUTSET OF THE WEEK-2 PERIOD. THIS FEATURE LEADS TO
ANOMALOUSLY WARM TEMPERATURES OVER MUCH OF THE WEST AND, WHILE STILL EARLY IN
THE SEASON, AN INCREASED CHANCE FOR EXTREME HEAT OVER THE SOUTHWEST. THE
NATIONAL BLEND OF MODELS (NBM) AND UNCALIBRATED DYNAMICAL MODELS DEPICT THE
POTENTIAL FOR RECORD DAILY HIGH TEMPERATURES, POSSIBLY ABOVE 100 DEG F ACROSS
THE DESERT SOUTHWEST INTO THE SOUTHERN CALIFORNIA CENTRAL VALLEY. THE ECMWF
PROBABILISTIC EXTREMES TOOL (PET) DEPICTS HIGH PROBABILITIES (GREATER THAN 60
PERCENT) FOR MAXIMUM TEMPERATURES TO EXCEED THE 90TH CLIMATOLOGICAL PERCENTILE
OVER THESE AREAS, AND SKILL WEIGHTED CALIBRATED HEAT RISK GUIDANCE ALSO
INDICATES ELEVATED PROBABILITIES FOR HEAT TO EXCEED THE 90TH CLIMATOLOGICAL
PERCENTILE. THEREFORE, A MODERATE RISK FOR EXTREME HEAT IS POSTED ACROSS THE
DESERT SOUTHWEST INTO THE SOUTHERN CALIFORNIA CENTRAL VALLEY, MAY 11-13. A
SLIGHT RISK FOR EXTREME HEAT EXTENDS FARTHER NORTH THROUGH THE REMAINDER OF THE
CALIFORNIA CENTRAL VALLEY AND INTO SOUTHERN NEVADA, AND IS VALID THROUGH MAY 15.
THE 0Z ECMWF ENSEMBLE DEPICTS SOME POTENTIAL FOR TEMPERATURES NEAR OR ABOVE 90
DEG F ACROSS LOW ELEVATION VALLEY AREAS OF THE GREAT BASIN DURING WEEK-2.
HOWEVER, THE GEFS IS GENERALLY COOLER, AND THE HEAT RISK IS THEREFORE FOCUSED
ON WHERE THE STRONGEST AND MORE CONSISTENT HEAT SIGNALS ARE OVER THE SOUTHWEST.
DURING THE MIDDLE AND LATER PART OF WEEK-2, SOME OF THIS HEAT MAY SPREAD INTO
THE CENTRAL AND SOUTHERN HIGH PLAINS AS THE MID-LEVEL RIDGE SLOWLY SHIFTS
EASTWARD. HOWEVER, THE MAGNITUDE OF THE HEAT IS MORE UNCERTAIN AS THE RIDGE IS
FORECAST TO WEAKEN COMPARED TO EARLIER IN THE PERIOD. THERE ARE WEAK SIGNALS
FOR TEMPERATURES TO REACH THE LOW TO MID 90S DEG F ACROSS THE REGION AND TRENDS
WILL CONTINUE TO BE MONITORED FOR POSSIBLE HEAT RISK ADDITION IN FUTURE UPDATES.
A PERSISTENT TROUGH LINKED TO THE NEGATIVE PHASE OF THE NORTH ATLANTIC
OSCILLATION (-NAO) REMAINS FORECAST ACROSS THE GREAT LAKES AND NORTHEAST INTO
WEEK-2. THIS CONTINUES TO FAVOR BELOW-NORMAL TEMPERATURES ACROSS THE REGION.
DESPITE IT GETTING LATER INTO MAY, THE ECMWF AND GEFS PETS DEPICT PARTS OF THE
OHIO VALLEY, GREAT LAKES, APPALACHIANS, AND NORTHEAST HAVING AT LEAST A 20
PERCENT CHANCE MINIMUM TEMPERATURES FALL BELOW THE 15TH CLIMATOLOGICAL
PERCENTILE AND 40 DEG F EARLY IN WEEK-2. LATE SEASON FROSTS STILL CANNOT BE
RULED OUT ACROSS MORE NORTHERN AND HIGHER ELEVATION AREAS, AND THE SLIGHT RISK
FOR MUCH BELOW NORMAL TEMPERATURES REMAINS IN PLACE, MAY 11-12.
THIS SAME TROUGH ALSO FAVORS A FRONT TO EXTEND THROUGH THE EASTERN U.S. AND
ALONG THE GULF COAST. THE 0Z GEFS AND ECMWF BOTH DEPICT ENHANCED PRECIPITATION
ALONG THIS BOUNDARY, WITH A MORE CONVECTIVE ELEMENT POSSIBLE ACROSS THE
SOUTHEAST AND LOWER MISSISSIPPI VALLEY BEFORE TRANSITIONING TO A MID-LATITUDE
FRONTAL WAVE AS MOISTURE IS PULLED NORTHWARD INTO THE NORTHEAST. THE GEFS IS A
BIT FASTER WITH THE PROGRESSION OF THIS FEATURE COMPARED TO THE ECMWF, BUT BOTH
MODELS INDICATE A BROAD SWATH OF 0.75 TO 1.5 INCHES OF PRECIPITATION ACROSS THE
EAST IN ASSOCIATION WITH THIS SYSTEM JUSTIFYING A SLIGHT RISK OF HEAVY
PRECIPITATION FROM THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST, EXTENDING
NORTHWARD THROUGH THE MID-ATLANTIC AND NORTHEAST, MAY 11-13.
SOUTH OF THE AFOREMENTIONED FRONTAL BOUNDARY, ENHANCED SUBTROPICAL RIDGING
CONTINUES TO SUPPORT A SLIGHT RISK OF EXTREME HEAT ACROSS CENTRAL AND SOUTHERN
FLORIDA, MAY 11-12. THE GEFS AND ECMWF PETS DEPICT AT LEAST A 20 PERCENT CHANCE
MAXIMUM TEMPERATURES EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE AND 90 DEG F.
ANTECEDENT DRY CONDITIONS MAY ALSO HELP PUSH TEMPERATURES UPWARD FURTHER
JUSTIFYING THE INCREASED RISK. DYNAMICAL MODELS GENERALLY INDICATE HEAT SIGNALS
DECREASING ACROSS THE REGION AROUND THE MIDDLE OF WEEK-2.
OVER THE ALASKA REGION, MODELS INDICATE POSSIBLE SURFACE LOW FORMATION OVER THE
NORTHWESTERN GULF OF ALASKA WHICH COULD BRING UNSETTLED WEATHER TO SOUTHERN
PORTIONS OF THE STATE. HOWEVER, THE STRONGEST SIGNALS TIED TO THIS FEATURE ARE
DURING THE LATE WEEK-1 PERIOD, AND NO RELATED HAZARDS ARE POSTED IN TODAY'S
WEEK-2 OUTLOOK. RESIDUAL TROUGHING FAVORS GENERALLY NEAR- TO SLIGHTLY
BELOW-NORMAL TEMPERATURES OVER MOST OF THE STATE. 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: THOMAS COLLOW
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