660
FXUS21 KWNC 181816
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JUNE 18 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. SURFACE LOW DEVELOPMENT IN THE LEE OF THE
ROCKIES SUPPORTS AN INCREASED RISK OF HEAVY PRECIPITATION MAINLY ACROSS PARTS
OF THE MIDDLE AND UPPER MISSISSIPPI VALLEY EARLY IN THE PERIOD.
HAZARDS
SLIGHT RISK OF EXTREME HEAT FOR PARTS OF CALIFORNIA CENTRAL VALLEY, DESERT
SOUTHWEST, SOUTHERN HIGH PLAINS, FRI-SUN, JUN 26-28.
SLIGHT RISK OF EXTREME HEAT FOR PARTS OF THE FLORIDA PENINSULA, FRI-THU, JUN
26-JUL 2.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE EASTERN CENTRAL AND
NORTHERN PLAINS, UPPER AND MIDDLE MISSISSIPPI VALLEY, AND PARTS OF THE WESTERN
OHIO VALLEY AND GREAT LAKES, FRI-SUN, JUN 26-28.
DETAILED SUMMARY
FOR SUNDAY JUNE 21 - THURSDAY JUNE 25:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY JUNE 26 - THURSDAY JULY 02: COMPARED TO YESTERDAY, 500-HPA HEIGHT
ANOMALY FORECASTS FROM THE GEFS AND ECMWF ENSEMBLES GENERALLY FEATURE A LESS
AMPLIFIED PATTERN EARLY IN WEEK-2, WITH THE MEAN WEEK-2 HEIGHT FIELDS DEPICTING
FAIRLY MUTED POSITIVE HEIGHT ANOMALIES OVER PORTIONS OF THE CONUS. PERHAPS THE
MOST MEANINGFUL CHANGE IN THE ENSEMBLE GUIDANCE RESIDES IN THE ECMWF, WHICH
MAINTAINED AN AMPLIFIED RIDGE CENTER OVER THE NORTHWESTERN CONUS OVER THE PAST
FEW DAYS, BUT NOW FAVORS A CONSIDERABLY MORE WESTWARD MEAN SOLUTION OF THIS
HEIGHT FEATURE OVER THE EASTERN PACIFIC IN THE LATEST 0Z RUN. THIS SHIFT FALLS
MORE IN LINE WITH THE GEFS, AND COULD ALLOW FOR MORE TROUGHING OVER THE
NORTHWESTERN CONUS AND POTENTIALLY FORCE RISING MID-LEVEL HEIGHTS DOWNSTREAM
LATER IN THE WEEK-2 PERIOD. OVER THE LOWER LATITUDES, THERE CONTINUES TO BE
GOOD MODEL AGREEMENT FEATURING ENHANCED SUBTROPICAL RIDGING TO INCREASE CHANCES
FOR ABOVE-NORMAL TEMPERATURES WITH POSSIBLE HEAT CONDITIONS DEVELOPING OVER THE
PARTS OF THE WEST COAST, LOWER FOUR CORNERS, AND THE GULF STATES DURING THE
PERIOD.
ANALYSIS OF ECMWF AND GEFS 500-HPA HEIGHT ANOMALIES IN STANDARDIZED SPACE
CONTINUES SHOWS A FAIRLY STRONG HEIGHT MAXIMA CENTERED OVER NORTHWESTERN MEXICO
EARLY IN THE PERIOD SUPPORTIVE OF EXTREME HEAT RISK. WITH PROBABILISTIC EXTREME
TOOLS (PETS) ALSO INDICATING AT LEAST 20% CHANCES OF DAYTIME TEMPERATURES
EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE TIED TO THIS HEIGHT FEATURE, A
SLIGHT RISK OF EXTREME HEAT REMAINS POSTED FOR PORTIONS OF THE CALIFORNIA
VALLEY, DESERT SOUTHWEST AND PARTS OF THE SOUTHERN PLAINS, AND REMAINS VALID
THROUGH JUN 28 BEFORE THE RIDGE CENTER DEAMPLIFIES. WITHIN THE HIGHLIGHTED
HAZARD AREA, RAW TEMPERATURE TOOLS CONTINUE TO DEPICT INCREASED CHANCES FOR
MAXIMUM TEMPERATURES EXCEEDING 105 DEG F OVER PARTS OF THE CALIFORNIA VALLEY,
AND OVER 110 DEG F OVER THE LOWER ELEVATIONS OF THE DESERT SOUTHWEST.
ALTHOUGH NEAR TO BELOW NORMAL DAYTIME TEMPERATURES ARE LARGELY FAVORED EAST OF
THE ROCKIES, THE PETS CONTINUE TO HIGHLIGHT INCREASED CHANCES FOR MAXIMUM
TEMPERATURES EXCEEDING THE 85TH PERCENTILE ACROSS PARTS OF 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 26-JUL 2) 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.
SINCE YESTERDAY, PETS ALSO SHOW A NORTHWARD EXPANSION OF WARM SIGNALS INTO THE
LOWER EASTERN SEABOARD BEGINNING BY DAYS 9-10 (JUN 27-28). THE GEFS IS A BIT
MORE AGGRESSIVE WITH THIS EXPANSION COMPARED TO THE ECMWF, BUT REGARDLESS,
THERE IS NOT MUCH SUPPORT FOR ACTUAL TEMPERATURES EXCEEDING HAZARD THRESHOLDS
BASED ON THE RAW TOOLS. THEREFORE, NO ADJUSTMENTS ARE MADE TO THE AREA
HIGHLIGHTED WITH A SLIGHT RISK OF EXTREME HEAT IN TODAY'S OUTLOOK, HOWEVER THIS
POTENTIAL WILL CONTINUE TO BE MONITORED IN THE COMING DAYS.
FOR PRECIPITATION, MODELS CONTINUE TO POINT TO POTENTIAL SURFACE LOW
DEVELOPMENT IN THE LEE OF ROCKIES EARLY IN WEEK-2, HOWEVER ENSEMBLE SOLUTIONS
REMAIN QUITE DIFFUSE IN REGARDS TO THE LOCATION OF DEVELOPMENT AND THE EVENTUAL
TRACK OF SURFACE LOW. DESPITE THIS, RAW UNCALIBRATED PRECIPITATION TOOLS HAVE
COME INTO BETTER AGREEMENT CONVERGING ON THE GREATEST PRECIPITATION RISK
CENTERED OVER THE UPPER AND MIDDLE MISSISSIPPI VALLEY WITH AT LEAST 20% CHANCES
FOR 3-DAY AMOUNTS EXCEEDING AN INCH. ADDITIONALLY, THERE IS ALSO BETTER
AGREEMENT IN THE GEFS AND ECMWF PETS HIGHLIGHTING THIS PART OF THE MIDWEST WITH
20% CHANCES OF 3-DAY AMOUNTS EXCEEDING THE 85TH PERCENTILE AND 1 INCH,
SUPPORTING THE ADDITION OF A SLIGHT RISK OF HEAVY PRECIPITATION, VALID FOR JUN
26-28 FOR THIS REGION. DUE TO THE SLIGHT RISK FOR EXCESSIVE RAINFALL FORECAST
DURING WEEK-1 ACROSS PARTS OF LOWER MISSOURI RIVER AND OHIO RIVER BASINS, ANY
HEAVY PRECIPITATION REALIZED MAY TRIGGER LOCALIZED FLOODING DURING WEEK-2.
NO HAZARDS ARE POSTED OVER ALASKA. FAVORED RIDGING ALOFT AND WARMER THAN
NORMAL CONDITIONS OVER PARTS OF THE MAINLAND MAY LEAD TO INCREASED AIR MASS
THUNDERSTORM ACTIVITY, SUPPORTIVE OF FIRE WEATHER DURING THE PERIOD.
FORECASTER: NICK NOVELLA
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