983
FXUS21 KWNC 041805
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT MAY 04 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 THE SOUTHWEST INTO THE CALIFORNIA CENTRAL VALLEY, AND GRADUALLY
SHIFTING INTO PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS. 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.
HAZARDS
MODERATE RISK OF EXTREME HEAT ACROSS THE SOUTHERN CALIFORNIA CENTRAL VALLEY,
TUE, MAY 12.
MODERATE RISK OF EXTREME HEAT ACROSS PORTIONS OF THE DESERT SOUTHWEST, TUE-WED,
MAY 12-13.
SLIGHT RISK OF EXTREME HEAT ACROSS PORTIONS OF THE SOUTHWESTERN CONUS AND THE
CALIFORNIA CENTRAL VALLEY, TUE-FRI, MAY 12-15.
SLIGHT RISK OF EXTREME HEAT ACROSS PORTIONS OF THE SOUTHERN PLAINS EXTENDING
INTO SOUTHERN KANSAS, WED-FRI, MAY 13-15.
SLIGHT RISK OF EXTREME HEAT ACROSS CENTRAL AND SOUTHERN FLORIDA, TUE, MAY 12.
SLIGHT RISK OF MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE GREAT
LAKES, OHIO VALLEY, APPALACHIANS, AND NORTHEAST, TUE-WED, MAY 12-13.
SLIGHT RISK OF HIGH WINDS ACROSS THE NORTHERN COAST OF CALIFORNIA AND COASTAL
OREGON, TUE-THU, MAY 12-14.
DETAILED SUMMARY
FOR THURSDAY MAY 07 - MONDAY MAY 11:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY MAY 12 - MONDAY MAY 18: THE 0Z ECMWF, GEFS, AND CANADIAN ENSEMBLES
DEPICT A STRONG MID-LEVEL RIDGE (+120 METER POSITIVE HEIGHT ANOMALY) OVER THE
WESTERN CONUS LATE IN WEEK-1 AND CONTINUING INTO THE START OF WEEK-2. 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. THE ECMWF AND GEFS ENSEMBLES ARE QUICKER TO FLATTEN
THE RIDGE COMPARED TO YESTERDAY, AND SHIFT IT TOWARD THE PLAINS BY THE MIDDLE
OF THE PERIOD. THEREFORE, WHILE INCREASED HEAT IS LIKELY ACROSS THE SOUTHWEST,
IT IS FORECAST TO BE TRANSIENT, WITH IMPACTS STARTING PRIOR TO THE START OF
WEEK-2. A MODERATE RISK FOR EXTREME HEAT REMAINS IN PLACE OVER THE SOUTHERN
CALIFORNIA CENTRAL VALLEY THROUGH DAY-8 (MAY 12), AND ACROSS THE DESERT
SOUTHWEST ON DAYS 8 AND 9 (MAY 12-13). 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 SUBSTANTIAL HEATING FORECAST ACROSS THE WEST FAVORS THERMAL LOW DEVELOPMENT
AND AN INCREASED PRESSURE GRADIENT ALONG PARTS OF THE WEST COAST. THE
UNCALIBRATED 0Z GEFS AND ECMWF ENSEMBLES BOTH SHOW ENHANCED PROBABILITIES FOR
WIND SPEEDS ABOVE 25-MPH ACROSS COASTAL PORTIONS OF NORTHERN CALIFORNIA AND
OREGON EARLY IN WEEK-2, AND THIS SIGNAL IS ALSO APPARENT IN THE PETS.
THEREFORE, A SLIGHT RISK OF HIGH WINDS IS POSTED ACROSS THESE AREAS, MAY 12-14.
AS THE RIDGE AXIS SHIFTS INTO THE SOUTH-CENTRAL CONUS, A WARMING TREND IS
LIKELY ACROSS THE CENTRAL AND SOUTHERN PLAINS. HIGH TEMPERATURES IN THE MID TO
UPPER 90S DEG F ARE DEPICTED IN THE UNCALIBRATED 0Z GEFS AND ECMWF ENSEMBLES
ACROSS PARTS OF WESTERN TEXAS AND OKLAHOMA, EXTENDING INTO SOUTHERN KANSAS,
WITH DAILY RECORDS BEING DEPICTED IN THE NBM TOWARD THE MIDDLE OF WEEK-2. AREAS
OF EXTREME DROUGHT ACROSS THE TEXAS PANHANDLE INTO WESTERN OKLAHOMA ALSO FAVOR
HOTTER TEMPERATURES. DUE TO THESE SIGNALS, IN ADDITION TO SUPPORT FROM CPC HEAT
RISK GUIDANCE AND THE PETS, A SLIGHT RISK OF EXTREME HEAT IS INTRODUCED ACROSS
PORTIONS OF THE SOUTHERN PLAINS INTO SOUTHERN KANSAS, MAY 13-15.
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 12-13.
DYNAMICAL MODELS CONTINUE TO INDICATE A FRONTAL SYSTEM ACROSS THE EASTERN U.S.
LATE IN WEEK-1. HOWEVER, THIS SYSTEM IS QUICK TO EXIT WITH MOST PRECIPITATION
TIMING OFF PRIOR TO THE START OF WEEK-2, WITH ONLY LINGERING AREAS OF
PRECIPITATION POSSIBLE INTO DAY-8 (MAY 12). THEREFORE, THE SLIGHT RISK OF HEAVY
PRECIPITATION ACROSS THE EAST IS REMOVED IN TODAY'S OUTLOOK.
ENHANCED SUBTROPICAL RIDGING CONTINUES TO SUPPORT A SLIGHT RISK OF EXTREME HEAT
ACROSS CENTRAL AND SOUTHERN FLORIDA, MAY 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 BY DAY-9 (MAY 13)
FOLLOWING A FRONTAL PASSAGE, BUT RELATIVELY WARMER TEMPERATURES MAY AGAIN
RETURN BY THE END OF THE PERIOD.
OVER THE ALASKA REGION, SURFACE LOW PRESSURE ACROSS THE BERING SEA FAVORS
INCREASED SOUTHERLY FLOW AND OCCASIONAL ENHANCED PRECIPITATION AND GUSTY WINDS
ALONG THE SOUTHERN AND SOUTHEAST COASTS. HOWEVER, HAZARDS CRITERIA ARE NOT
ANTICIPATED TO BE REACHED. 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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