239
FXUS21 KWNC 301803
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JUNE 30 2026
SYNOPSIS: BUILDING MID-LEVEL HIGH PRESSURE OVER PARTS OF THE WESTERN AND
CENTRAL CONTIGUOUS U.S. (CONUS) SUPPORTS ABOVE-NORMAL SUMMERTIME TEMPERATURES
WITH AN INCREASED HEAT RISK EXTENDING FROM THE DESERT SOUTHWEST INTO THE UPPER
MIDWEST EARLY IN WEEK-2. FURTHER SOUTH, ENHANCED SUBTROPICAL HIGH PRESSURE ALSO
FAVORS THE POTENTIAL FOR EXTREME HEAT CONDITIONS FOR PARTS OF FLORIDA DURING
THE PERIOD. ABOVE THE SUBTROPICAL MID-LEVEL HIGH PRESSURE, THERE IS BETTER
MODEL SUPPORT FOR SURFACE LOW DEVELOPMENT AND AN ACCOMPANYING HEAVY
PRECIPITATION RISK OVER PARTS OF THE SOUTHEAST AND MID-ATLANTIC. OVER THE WEST
COAST, STRENGTHENING PRESSURE GRADIENTS FAVORED LEADS TO INCREASED CHANCES FOR
EPISODES OF HIGH WINDS ACROSS THE PACIFIC NORTHWEST AND CALIFORNIA FOR MUCH OF
THE PERIOD.
HAZARDS
SLIGHT RISK OF EXTREME HEAT ACROSS MUCH OF THE GREAT BASIN, NORTHERN
INTERMOUNTAIN, ROCKIES, SOUTHWEST, AND GREAT PLAINS, WED-FRI, JUL 8-10.
SLIGHT RISK OF EXTREME HEAT FOR THE EASTERN GULF COAST AND FLORIDA PENINSULA,
WED-SUN, JUL 8-12.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE MID-ATLANTIC AND THE
SOUTHEAST, WED-FRI, JUL 8-10.
SLIGHT RISK OF EPISODIC HIGH WINDS FOR PORTIONS OF CALIFORNIA AND THE PACIFIC
NORTHWEST, WED-TUE, JUL 8-14.
DETAILED SUMMARY
FOR FRIDAY JULY 03 - TUESDAY JULY 07:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY JULY 08 - TUESDAY JULY 14: A SIGNIFICANT HEAT EVENT REMAINS
FAVORED FOR MUCH OF THE CENTRAL AND EASTERN CONUS DURING WEEK-1, WITH HEAT
RISKS EXPECTED TO SHIFT WESTWARD AND POTENTIALLY LINGER INTO WEEK-2 ASSOCIATED
WITH A RETROGRADING 500-HPA RIDGE BY EARLY NEXT WEEK. MID-LEVEL HEIGHT ANOMALY
FORECASTS FROM THE TODAY'S 0Z GEFS AND ECMWF ENSEMBLES ARE IN GOOD AGREEMENT BY
THE OUTSET OF WEEK-2 (JUL 8), BOTH FEATURING A 594 DM HEIGHT CENTER OVER THE
FOUR CORNERS, WITH THE STRONGEST POSITIVE HEIGHT DEPARTURES FOCUSED OVER THE
NORTHERN PLAINS AND SOUTHCENTRAL CANADA. THIS MID-LEVEL PATTERN SHOULD ALLOW
FOR MORE MEAN NORTHWESTERLY FLOW TO BRING COOLER TEMPERATURES AND HEAT RELIEF
FOR AREAS DOWNSTREAM MAINLY EAST OF THE MISSISSIPPI, HOWEVER THE GREATEST
POTENTIAL FOR CONTINUING HEAT RISK RESIDES ALONG THIS RIDGE AXIS EXTENDING FROM
THE SOUTHWESTERN CONUS INTO THE UPPER MIDWEST EARLY IN WEEK-2. IN ADDITION,
ENHANCED SUBTROPICAL RIDGING REMAINS A FACTOR ACROSS THE LOWER LATITUDES LATER
NEXT WEEK. WHILE THE GEFS IS RELATIVELY WEAKER WITH THIS POTENTIAL, THE ECMWF
PLACES A SECONDARY 594 DM HEIGHT CENTER OVER THE EASTERN GULF OF AMERICA. THIS
TRANSLATES TO HEIGHT ANOMALIES THAT ARE GREATER THAN 3 STANDARD DEVIATIONS
ABOVE NORMAL, SUPPORTIVE OF AN INCREASED HEAT RISK OVER THE EASTERN GULF OF
AMERICA DURING THE PERIOD. OVER TIME, DIVERGING MID-LEVEL HEIGHT FORECASTS FROM
GEFS AND ECMWF RESULT IN INCREASINGLY VARIED TEMPERATURE SOLUTIONS. THE GEFS
FAVORS A MORE STABLE RIDGE PATTERN OVER THE INTERIOR WEST WITH DEEPER TROUGHING
DEVELOPING OVER THE EASTERN CONUS, WHEREAS THE ECMWF REESTABLISHES A HEIGHT
ANOMALY CENTER OVER THE UPPER MIDWEST AND GREAT LAKES LEADING TO HIGHER ODDS
FOR ABOVE-NORMAL TEMPERATURES AND POSSIBLE RENEWED HEAT RISKS OVER THE
NORTHEASTERN CONUS.
BASED ON GOOD AGREEMENT AMONG TEMPERATURE TOOLS AMONG THE MODELS EARLY IN
WEEK-2, A SLIGHT RISK OF EXTREME HEAT REMAINS ISSUED EXTENDING FROM THE
SOUTHWESTERN CONUS NORTHEASTWARD TO THE UPPER MIDWEST FOR IN PROXIMITY TO THE
RIDGE AXIS FAVORED. COVERAGE HAS BEEN ADJUSTED TO INCLUDE MORE PORTIONS OF THE
INTERIOR WEST, AND IS NOW VALID THROUGH JUL 10 BEFORE THE RIDGING POTENTIALLY
DEAMPLIFIES AS ADVERTISED IN THE ECMWF ENSEMBLE. WITHIN THE HIGHLIGHTED SLIGHT
RISK AREA, PROBABILISTIC EXTREME TOOLS (PETS) INDICATE 10-40% CHANCES OF
DAYTIME TEMPERATURES EXCEEDING THE 85TH PERCENTILE AND RAW TEMPERATURE TOOLS
SHOW THE GREATEST SIGNALS FOR POSITIVE TEMPERATURE DEPARTURE FROM NORMAL
EXCEEDING 5 AND 10 DEG F. WITH THE HOTTEST TEMPERATURES FAVORED OVER THE DESERT
SOUTHWEST, A MODERATE RISK OF EXTREME HEAT WAS CONSIDERED BASED ON STRONGER
SUPPORT IN THE GEFS PET AND INCREASING HEAT SIGNALS IN THE NWS PROBABILISTIC
HEAT RISK TOOL, HOWEVER, THIS RISK IS LESS SUPPORTED IN THE ECMWF PET WHICH
SHOWS LESS THAN 20% CHANCES FOR MAXIMUM TEMPERATURES EXCEEDING THE 85TH
PERCENTILE OVER THE LOWER FOUR CORNERS. THE OMISSION OF A HIGHER RISK
DESIGNATION IS ALSO CONSISTENT WITH THE NATIONAL BLEND OF MODELS (NBM) WHICH
MAINTAIN DAYTIME HIGHS BELOW 110, AND ECMWF PRECIPITATION PET DEPICTING WETTER
CONDITIONS ASSOCIATED WITH THE SOUTHWESTERN MONSOON, WHERE INCREASED CLOUDINESS
AND PRECIPITATION WOULD KEEP ANY ELEVATED HEAT POTENTIAL AT BAY EARLY IN THE
PERIOD. BY DAY 10 (JUL 10) AND BEYOND, THE DIVERGING MID-LEVEL HEIGHT SOLUTIONS
RESULT IN ANOMALOUS TEMPERATURE PATTERNS THAT NEARLY BECOME OUT OF PHASE WITH
ONE ANOTHER OVER THE MID-LATITUDES. WITH THE GEFS (ECMWF) PETS FOCUSING THE
STRONGEST SIGNALS FOR ANOMALOUS WARMTH AND POTENTIAL HEAT ACROSS THE WESTERN
(NORTHEASTERN) CONUS, THERE IS ADDED UNCERTAINTY PRECLUDING ANY ADDITIONAL
TEMPERATURE RELATED HAZARDS BEING POSTED IN THE UPDATED OUTLOOK.
TIED TO THE STRONG SUBTROPICAL RIDGING OVER THE GULF AND WESTERN ATLANTIC, A
SLIGHT RISK OF EXTREME HEAT IS ALSO POSTED OVER THE EASTERN GULF COAST AND
FLORIDA PENINSULA WHERE BOTH PETS SHOW INCREASED CHANCES FOR DAYTIME
TEMPERATURES EXCEEDING THE 85TH PERCENTILE THROUGH THE MIDDLE OF WEEK-2. THIS
RISK IS ALSO SUPPORTED BY THE DETERMINISTIC NBM DEPICTING APPARENT TEMPERATURES
ABOVE 100 DEG F LATE NEXT WEEK, AND VERY WARM SEA SURFACE TEMPERATURES IN THE
EASTERN GULF, WITH ANOMALIES REGISTERING UPWARDS OF 1.5 TO 2 DEG C ABOVE
NORMAL. THE NBM ALSO CONTINUES TO SHOW A NUMBER OF LOCATIONS WITH VERY WARM
NIGHTTIME LOWS APPROACHING AND/OR BREAKING RECORDS ALONG THE GULF COAST THROUGH
LATE NEXT WEEK.
WITH MORE MID-LEVEL TROUGHING FAVORED OVER THE EASTERN U.S. TOWARDS THE MIDDLE
OF NEXT WEEK, THERE IS GROWING ENSEMBLE SUPPORT FOR SURFACE LOW DEVELOPMENT
POTENTIALLY AFFECTING PARTS OF THE SOUTHEAST AND MID-ATLANTIC. STRENGTHENING
LOW MEMBERS OVER THE LOWER EASTERN SEABOARD AND JUST OFFSHORE IN WESTERN
ATLANTIC ARE ALSO REFLECTED IN PROBABILISTIC ECMWF AND GOOGLE AI TROPICAL
CYCLONE DEVELOPMENT TOOLS. AS IS OFTEN THE CASE WITH THESE TYPES OF OFFSHORE
LOWS, THERE IS HIGH UNCERTAINTY AS TO WHETHER ANY LOW THAT DEVELOPS WILL
ACQUIRE TROPICAL CHARACTERISTICS, BUT SUCH A REALIZATION CANNOT BE RULED OUT.
REGARDLESS, ENHANCED PRECIPITATION IS FAVORED TO ACCOMPANY ANY DEVELOPING
SURFACE LOW AND PETS ARE BEGINNING TO CONVERGE ON AN INCREASED HEAVY
PRECIPITATION RISK OVER PARTS OF THE MID-ATLANTIC AND SOUTHEAST. GIVEN THIS, AS
WELL AS RAW TOOLS NOW FAVORING 20-40% CHANCES FOR 3-DAY AMOUNTS EXCEEDING AN
INCH WHERE PETS INDICATE GROWING SIGNALS IN PERCENTILE SPACE, A SLIGHT RISK OF
HEAVY PRECIPITATION IS ISSUED FOR JUL 8-10. WITHIN THE HIGHLIGHTED SLIGHT RISK
AREA, LOCALIZED URBAN FLOODING IS POSSIBLE. IN ADDITION TO THE AFOREMENTIONED
WET TREND EVIDENT IN THE ECMWF PET OVER THE DESERT SOUTHWEST, THE GEFS PET ALSO
SHOWS INCREASED CHANCES FOR 3-DAY AMOUNTS EXCEEDING THE 85TH PERCENTILE, BUT TO
A WEAKER EXTENT. EVEN WITH THESE INCREASED SIGNALS IN BOTH THE PETS SINCE
YESTERDAY, RAW AND CALIBRATED MEAN PRECIPITATION AMOUNTS, AS WELL AS CHANCES
FOR AMOUNTS EXCEEDING A HALF AN INCH STILL REMAIN FAIRLY LOW OVER THE LOWER
FOUR CORNERS, PRECLUDING A CORRESPONDING PRECIPITATION HAZARD AT THIS TIME.
LOCALIZED THUNDERSTORMS ARE STILL POSSIBLE AND THIS AREA WILL CONTINUE TO BE
MONITORED WITH ENSEMBLE GUIDANCE INDICATING PRECIPITABLE WATER INCREASING
DURING THE WEEK-2 PERIOD.
SURFACE HIGH PRESSURE OFF THE WEST COAST ALONG WITH THERMALLY INDUCED LOW
PRESSURE OVER THE GREAT BASIN AND DESERT SOUTHWEST INCREASE CHANCES FOR
EPISODES OF HIGH WINDS DURING WEEK-2. THE GEFS AND ECMWF PETS CONTINUE TO
INDICATE AT LEAST A 20 PERCENT CHANCE OF WIND SPEEDS EXCEEDING THE 85TH
CLIMATOLOGICAL PERCENTILE. THEREFORE, A SLIGHT RISK OF HIGH WINDS REMAINS
POSTED ACROSS THIS REGION, JUL 8-14. IT SHOULD BE NOTED THAT ANY SUBSTANTIAL
INCREASE IN MONSOONAL MOISTURE AND PRECIPITATION WILL BRING COOLER
TEMPERATURES, WHICH IS LIKELY TO BREAK DOWN THE THERMAL LOW PRESSURE AND WEAKEN
THIS HIGH WIND POTENTIAL DURING THE PERIOD.
FORECASTER: NICK NOVELLA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page