039
FXUS21 KWNC 172126
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JUNE 17 2026
SYNOPSIS: FORECAST MID-LEVEL HIGH PRESSURE OVER THE SOUTHWESTERN CONTIGUOUS
U.S. (CONUS) IS EXPECTED TO PROMOTE ABOVE-NORMAL TEMPERATURES WITH POSSIBLE
EXTREME HEAT CONDITIONS ACROSS THE CALIFORNIA VALLEY EASTWARD INTO THE LOWER
FOUR CORNERS LATER NEXT WEEK. ENHANCED SUBTROPICAL HIGH PRESSURE OVER THE GULF
OF AMERICA AND WESTERN ATLANTIC ALSO BRINGS AN INCREASED RISK OF HEAT OVER
PORTIONS OF FLORIDA DURING WEEK-2. ABOVE-NORMAL PRECIPITATION IS PREDOMINATELY
FAVORED OVER MUCH OF THE MIDWEST EARLY IN WEEK-2, HOWEVER THERE CONTINUES TO BE
OUTLOOK UNCERTAINTY IN REGARDS TO DESIGNATING A CORRESPONDING HEAVY
PRECIPITATION RISK.
HAZARDS
SLIGHT RISK OF EXTREME HEAT FOR PARTS OF CALIFORNIA CENTRAL VALLEY, DESERT
SOUTHWEST, SOUTHERN HIGH PLAINS, THU-SUN, JUN 25-28.
SLIGHT RISK OF EXTREME HEAT FOR FLORIDA, THU-WED, JUN 25-JUL 1.
DETAILED SUMMARY
FOR SATURDAY JUNE 20 - WEDNESDAY JUNE 24:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY JUNE 25 - WEDNESDAY JULY 01: TOWARDS THE MIDDLE OF NEXT WEEK,
DYNAMICAL MODEL 500-HPA HEIGHT ANOMALY FORECASTS FROM THE GEFS AND ECMWF
ENSEMBLES CONTINUE TO BE AT ODDS WITH ONE ANOTHER IN REGARDS TO THE SHAPE AND
EVOLUTION OF THE MID-LEVEL PATTERN OVER THE NORTHWESTERN CONUS AND EASTERN
PACIFIC, CONTRIBUTING TO INCREASED UNCERTAINTY IN THE HAZARD OUTLOOK.
CONSISTENT WITH PREVIOUS ENSEMBLE RUNS, THE GEFS FAVORS THE DEVELOPMENT OF
SHORTWAVE TROUGHING OVER THE PACIFIC NORTHWEST, WHEREAS THE ECMWF ENSEMBLE
REMAINS BULLISH IN MAINTAINING ABOVE-NORMAL HEIGHT DEPARTURES, RESULTING IN
CONTRASTING TEMPERATURE RESPONSES OVER THIS PART OF THE COUNTRY EARLY IN
WEEK-2. DOWNSTREAM, THERE IS GENERAL MODEL AGREEMENT FEATURING BROADLY WEAK
MEAN LONGWAVE TROUGHING EAST OF THE ROCKIES, WITH WEAKER SUBTROPICAL RIDGING
OVER THE SOUTHERN TIER OF THE U.S. BOTH OF THESE FEATURES ARE EXPECTED TO
BRING COOLER TEMPERATURES OVER PARTS OF THE GREAT PLAINS, MISSISSIPPI,
TENNESSEE, AND OHIO VALLEYS HEADING INTO THE WEEK-2 PERIOD, HOWEVER PARTS OF
THE EASTERN GULF COAST AND FLORIDA COULD STRUGGLE TO EXPERIENCE RELIEF FROM
ABOVE-NORMAL TEMPERATURES LINGERING FROM WEEK-1.
TIED TO STRONGER SHORTWAVE TROUGHING OVER THE NORTHWESTERN CONUS IN THE LATEST
0Z GEFS, THE CORRESPONDING RAW AND CALIBRATED TEMPERATURE TOOLS INDICATE NEAR
TO BELOW NORMAL DAYTIME TEMPERATURES, ALONG WITH A DOWNTICK IN HEAT SIGNALS IN
THE PROBABILISTIC EXTREMES TOOL (PET). WHILE ABOVE-NORMAL TEMPERATURES AND HEAT
CONDITIONS REMAIN POSSIBLE ACROSS THIS REGION AS ADVERTISED BY THE ECMWF AND
CANADIAN ENSEMBLES, DETERMINISTIC SOLUTIONS FROM THE ECWMF AND GFS ALSO POINT
TO THE POTENTIAL FOR SHORTWAVE DEVELOPMENT, RESULTING IN INSUFFICIENT
CONFIDENCE OF MAINTAINING A SLIGHT RISK OF EXTREME HEAT OVER PARTS OF THE
PACIFIC NORTHWEST AND NORTHERN INTERMOUNTAIN IN THE UPDATED OUTLOOK. HOWEVER, A
SLIGHT RISK OF EXTREME HEAT REMAINS POSTED FURTHER SOUTH ACROSS THE PORTIONS OF
THE CALIFORNIA VALLEY AND THE LOWER FOUR CORNERS WHERE THERE IS BETTER
AGREEMENT IN THE MID-LEVEL HEIGHT AND TEMPERATURE FORECASTS AMONG THE DYNAMICAL
MODELS. WITHIN THE HIGHLIGHTED REGION, BOTH GEFS AND ECMWF PETS INDICATE AT
LEAST 20% CHANCES FOR MAXIMUM TEMPERATURES EXCEEDING THE 85TH CLIMATOLOGICAL
PERCENTILE, WITH SIMILAR CHANCES FOR ACTUAL TEMPERATURES EXCEEDING 100 (110)
DEG F IN PARTS OF THE CALIFORNIA VALLEY (DESERT SOUTHWEST) EARLY IN WEEK-2. THE
SLIGHT RISK COVERAGE IS ADJUSTED TO REMOVE PARTS OF THE TEXAS WHERE COOLER
TEMPERATURES ARE FORECAST EARLY IN WEEK-2, AND IS NOW VALID THROUGH JUN 28 AS
THE RIDGING ALOFT GRADUALLY DEAMPLIFIES. DESPITE THE COOLER TEMPERATURES
FAVORED DOWNSTREAM, THE PETS CONTINUE TO HIGHLIGHT INCREASED CHANCES FOR
MAXIMUM TEMPERATURES EXCEEDING THE 85TH PERCENTILE OVER THE FLORIDA ASSOCIATED
WITH PERSISTENT ENHANCED SUBTROPICAL RIDGING OVER THE GULF AND WESTERN ATLANTIC
THROUGHOUT THE PERIOD. THEREFORE, A SLIGHT RISK OF EXTREME HEAT REMAINS POSTED
(JUN 25-JUL 1) WITH COVERAGE LIMITED TO THE FLORIDA PENINSULA IN THE UPDATED
OUTLOOK. THE NATIONAL BLEND OF MODELS (NBM) ALSO CONTINUES TO DEPICT A NUMBER
OF LOCATIONS WITH NEAR RECORD HIGH MINIMUM TEMPERATURES OVER FLORIDA LATER NEXT
WEEK SUGGESTIVE OF LITTLE RELIEF OF POTENTIAL HEAT DURING THE OVERNIGHT HOURS.
SURFACE LOW DEVELOPMENT IN THE LEE OF THE ROCKIES AND ASSOCIATED ENHANCED
LIKELIHOOD OF HEAVY PRECIPITATION IS POSSIBLE EARLY IN THE PERIOD, HOWEVER THE
GEFS AND ECMWF DIFFER IN REGARDS TO THE PLACEMENT AND STRENGTH OF ANY
DISCERNIBLE MEAN SURFACE LOW. A MORE WESTERLY SOLUTION OF A MEAN LOW PRESSURE
CENTER IS FOUND IN THE GEFS TIED TO THE SHORTWAVE TROUGHING UPSTREAM, WHEREAS
THE ECMWF FAVORS LOWERED MEAN SURFACE PRESSURE EXTENDING FROM THE GREAT PLAINS
TO THE GREAT LAKES WITH A ROBUST PRECIPITATION REFLECTION FOCUSED OVER THE
MIDDLE MISSISSIPPI VALLEY IN ITS PRECIPITATION TOOLS. IN PARTICULAR, THE
UNCALIBRATED ECMWF INDICATES 40% CHANCES OF 3-DAY AMOUNTS EXCEEDING AN INCH
OVER PARTS OF IOWA, MISSOURI EASTWARD TO THE OHIO VALLEY. THIS RISK HOWEVER IS
MUCH LESS SUPPORTED IN THE GEFS, GEFSAI AND CANADIAN GUIDANCE PRECLUDING ANY
CORRESPONDING PRECIPITATION HAZARDS IN THE OUTLOOK. THIS POTENTIAL WILL
CONTINUE TO BE MONITORED IN THE COMING DAYS.
DUE TO AFOREMENTIONED DISAGREEMENTS IN THE HEIGHT PATTERN AMONG THE DYNAMICAL
MODELS, NO WIND HAZARDS ARE POSTED OVER THE CONUS. BOTH GEFS AND ECMWF PETS
SHOW INCREASED CHANCES FOR WIND SPEEDS EXCEEDING THE 85TH PERCENTILE ACROSS THE
WESTERN CONUS, HOWEVER THERE IS LITTLE TO NO SUPPORT FOR WIND SPEEDS EXCEEDING
HAZARD THRESHOLDS IN THE UNCALIBRATED TOOLS.
FORECASTER: NICK NOVELLA
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