395
FXUS21 KWNC 271805
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JUNE 27 2026
SYNOPSIS: EXTREME HEAT IS LIKELY TO CONTINUE FROM WEEK-1 INTO THE JULY 4TH
HOLIDAY WEEKEND ACROSS MANY AREAS OF THE CENTRAL AND EASTERN CONTIGUOUS U.S.
(CONUS) ASSOCIATED WITH ANOMALOUS MID-LEVEL HIGH PRESSURE. ANTICIPATED HIGH
DEWPOINTS FAVOR HEAT INDEX VALUES EXCEEDING 100 TO 105 DEG F OVER MANY AREAS
WITH WARM NIGHTS LIMITING OVERNIGHT RELIEF. AS THE MID-LEVEL HIGH SHIFTS
WESTWARD, SOME HEAT RELIEF IS FORECAST ACROSS THE EASTERN SEABOARD, BUT WITH
EXTREME HEAT POTENTIAL INCREASING ACROSS PARTS OF THE WESTERN CONUS. THIS
TRANSITION MAY ALSO FAVOR FRONTAL ACTIVITY AND HEAVY PRECIPITATION ACROSS
PORTIONS OF THE NORTHEAST AND MID-ATLANTIC EARLY IN THE PERIOD. SURFACE HIGH
PRESSURE OFF THE WEST COAST IN WEEK-2 INCREASES CHANCES FOR EPISODES OF HIGH
WINDS ACROSS THE PACIFIC NORTHWEST AND CALIFORNIA THROUGH MUCH OF THE PERIOD.
HAZARDS
MODERATE RISK OF EXTREME HEAT FOR THE EASTERN GREAT PLAINS, MISSISSIPPI AND
TENNESSEE VALLEYS, SOUTHEAST, AND MID-ATLANTIC, SUN, JUL 5.
SLIGHT RISK OF EXTREME HEAT ACROSS MUCH OF THE CENTRAL AND EASTERN CONUS,
SUN-TUE, JUL 5-7.
SLIGHT RISK OF EXTREME HEAT ACROSS MUCH OF THE GREAT BASIN, SOUTHWEST, AND
ROCKIES, SUN-THU, JUL 5-9.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE MID-ATLANTIC, CENTRAL
APPALACHIANS, AND EASTERN OHIO VALLEY, SUN-MON, JUL 5-6.
SLIGHT RISK OF HIGH WINDS FOR PORTIONS OF CALIFORNIA AND THE PACIFIC NORTHWEST,
SUN-SAT, JUL 5-11.
DETAILED SUMMARY
FOR TUESDAY JUNE 30 - SATURDAY JULY 04:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SUNDAY JULY 05 - SATURDAY JULY 11: A MAJOR HEAT WAVE IS FORECAST TO BE
ONGOING ACROSS MUCH OF THE CENTRAL AND EASTERN CONUS AT THE START OF WEEK-2.
FOR THE EASTERN SEABOARD, THE PEAK OF THE HEAT IS LIKELY TO OCCUR DURING THE
LATE WEEK-1 TIMEFRAME, WITH MID-LEVEL RIDGING RETROGRADING FARTHER TO THE WEST
AT THE BEGINNING OF WEEK-2. DESPITE THESE TRENDS, THE ECMWF PROBABILISTIC
EXTREME TOOL (PET) CONTINUES TO INDICATE GREATER THAN A 60 PERCENT CHANCE
MAXIMUM TEMPERATURES EXCEED THE 85TH CLIMATOLOGICAL PERCENTILE ON DAY-8 (JULY
5). ADDITIONALLY, THE UNCALIBRATED 0Z DETERMINISTIC ECMWF DEPICTS HEAT INDEX
VALUES AROUND 105 DEG F ACROSS THE MID-ATLANTIC. THE GEFS PET IS LESS ROBUST
WITH CHANCES FOR EXTREME HEAT BY DAY 8. HOWEVER, IT STILL DEPICTS ACTUAL
TEMPERATURES IN THE 90S DEG F EXTENDING THROUGH THE NORTHERN MID-ATLANTIC AND
POSSIBLY NEAR TO ABOVE 100 DEG F ACROSS PARTS OF THE CAROLINAS. GIVEN SOME OF
THE RELATIVELY COOLER SIGNALS EMERGING OVER MORE NORTHERN AREAS, THE RISKS OF
EXTREME HEAT HAVE BEEN ADJUSTED SLIGHTLY SOUTHWARD COMPARED TO YESTERDAY ACROSS
THE EAST. THE NATIONAL BLEND OF MODELS (NBM) RECORDS TOOL SHOWS A DRAMATIC
REDUCTION IN NEAR OR RECORD BREAKING HEAT BY JULY 5TH ACROSS THE EASTERN CONUS.
AS SUCH, THE HIGH RISK OF EXTREME HEAT HAS BEEN ALLOWED TO TIME OFF INTO THE
WEEK-1 PERIOD.
A MODERATE RISK (GREATER THAN 40 PERCENT CHANCE) FOR EXTREME HEAT REMAINS VALID
FOR JULY 5TH OVER THE CENTRAL AND SOUTHERN PORTIONS OF THE MID-ATLANTIC INTO
THE SOUTHEAST GIVEN THE BEST TOOL AGREEMENT AND CONTINUED CHANCES FOR HEAT
INDEX VALUES TO EXCEED 105 DEGF. THE MODERATE RISK EXTENDS WESTWARD THROUGH
PARTS OF THE TENNESSEE VALLEY, MISSISSIPPI VALLEY AND EASTERN PLAINS UNDERNEATH
THE RIDGE AXIS AND CONSISTENT WITH A VERY HUMID AIR MASS IN PLACE, WITH SKILL
WEIGHTED HEAT RISK TOOLS INDICATING AT LEAST A 40 PERCENT CHANCE OF HEAT INDEX
VALUES EXCEEDING 100 (105) DEG F INTO PARTS OF THE NORTHERN (CENTRAL &
SOUTHERN) PLAINS. THE NBM ALSO DEPICTS WIDESPREAD RECORD HIGH MINIMUM
TEMPERATURES THROUGHOUT MUCH OF THE EASTERN U.S. (POTENTIALLY ONLY DROPPING
INTO THE MID- TO UPPER 70S DEG F), RESULTING IN LITTLE OVERNIGHT RELIEF FROM
THE HEAT. STAYING HYDRATED AND LIMITING EXPOSURE TO VERY HOT, HUMID WEATHER IS
VERY IMPORTANT, ESPECIALLY FOR VULNERABLE POPULATIONS INCLUDING OLDER ADULTS. A
SLIGHT RISK (20-40 PERCENT CHANCE) OF EXTREME HEAT ENCOMPASSING THE MODERATE
RISK IS POSTED FROM THE GREAT PLAINS TO THE EASTERN SEABOARD FOR JULY 5-7.
BY DAY-9, THE 0Z ECMWF, GEFS, AND CANADIAN ENSEMBLES ALL DEPICT A 594-596 DM
RIDGE ACROSS THE FOUR CORNERS, WHICH COULD RESULT IN EXTREME HEAT CONDITIONS
EMERGING ACROSS PORTIONS OF THE INTERIOR WEST AND PERSISTING THROUGH AT LEAST
THE MIDDLE OF WEEK-2. THE WEATHER PREDICTION CENTER (WPC) PROBABILISTIC
HEATRISK TOOL SHOWS INCREASING SIGNALS FOR MAJOR HEATRISK ACROSS THE WEST BY
THE BEGINNING OF WEEK-2. THEREFORE, AN ADDITIONAL SLIGHT RISK (20-40 PERCENT
CHANCE) OF EXTREME HEAT IS VALID JULY 5-9, ACROSS MUCH OF THE INTERIOR WESTERN
US, EXCLUDING MOST AREAS WEST OF THE SIERRA NEVADA AND THE NORTHERN ROCKIES.
TIED TO WESTWARD SHIFTING RIDGING, AND THE POTENTIAL PROGRESSION OF FRONTAL
ACTIVITY, ENHANCED PRECIPITATION AND POTENTIAL THUNDERSTORMS ARE POSSIBLE
ACROSS PARTS OF THE EASTERN OHIO VALLEY, CENTRAL APPALACHIANS, AND
MID-ATLANTIC. WHILE SIGNALS ARE WEAK, CONSIDERATION IS GIVEN TO THE OVERALL
SYNOPTIC PATTERN AND INCREASED IMPACTS ON JULY 4TH WEEKEND. BOTH THE GEFS AND
ECMWF PETS INDICATE AT LEAST A 20 PERCENT CHANCE OF 3-DAY PRECIPITATION TOTALS
EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE ACROSS PARTS OF THE REGION.
UNCALIBRATED TOOLS ARE MARGINALLY SUPPORTIVE AS WELL WITH ENHANCED CHANCES OF
PRECIPITATION TOTALS REACHING 1-INCH, AND LOCALLY HIGHER AMOUNTS POSSIBLE IN
THUNDERSTORMS. THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED FOR
THE AFOREMENTIONED AREAS, JULY 5-6.
SURFACE HIGH PRESSURE OFF THE WEST COAST AND THERMAL LOW PRESSURE OVER THE
GREAT BASIN INCREASE CHANCES FOR EPISODES OF HIGH WINDS DURING WEEK-2. THE GEFS
AND ECMWF PETS INDICATE AT LEAST A 20 PERCENT CHANCE OF WIND SPEEDS EXCEEDING
THE 85TH CLIMATOLOGICAL PERCENTILE AND 25-MPH. THEREFORE, A SLIGHT RISK OF HIGH
WINDS IS POSTED ACROSS THIS REGION.
ACROSS THE SOUTHWESTERN CONUS, THE RIDGE AXIS IS FORECAST TO MOVE TOWARDS A
MORE FAVORABLE POSITION FOR ENHANCED MONSOONAL MOISTURE ADVECTION AND INCREASED
PRECIPITATION OVER PARTS OF THE DESERT SOUTHWEST. ALTHOUGH PETS SHOW INCREASED
CHANCES OF 3-DAY PRECIPITATION EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE
OVER THE DESERT SOUTHWEST AND INTO THE CENTRAL ROCKIES DURING THE SECOND HALF
OF WEEK-2, BOTH RAW AND CALIBRATED PRECIPITATION AMOUNTS IN THE ENSEMBLE MEANS
REMAIN FAIRLY LOW, 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.
TRANSIENT SHORTWAVES MOVING ACROSS ALASKA FAVOR PERIODS OF ENHANCED
PRECIPITATION ACROSS MUCH OF THE STATE, ALONG WITH A TILT TOWARD BELOW-AVERAGE
TEMPERATURES. HOWEVER, PRECIPITATION AND TEMPERATURE VALUES ARE EXPECTED TO
REMAIN BELOW HAZARDOUS THRESHOLDS.
FORECASTER: RYAN BOLT
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