553
FXUS21 KWNC 081759
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 08 2026
SYNOPSIS: HIGHLY AMPLIFIED MID-LEVEL HIGH PRESSURE IS FORECAST TO DEVELOP
ACROSS THE WESTERN AND CENTRAL CONTIGUOUS U.S. (CONUS) DURING WEEK-1 AND
PERSIST INTO WEEK-2. WHILE THERE IS SOME UNCERTAINTY IN THE DYNAMICAL MODELS
REGARDING THE WESTWARD PROGRESSION OF THIS FEATURE AND THE EXTENT OF MID-LEVEL
LOW PRESSURE DOWNSTREAM IN THE EAST, A BROAD AREA OF EXTREME HEAT IS LIKELY
ACROSS THE WESTERN, CENTRAL, AND SOUTHEASTERN CONUS THROUGHOUT THE PERIOD GIVEN
THE CLIMATOLOGICAL PEAK OF SUMMER TIME HEATING. THIS PATTERN IS ALSO EXPECTED
TO ENHANCE THE MONSOONAL CIRCULATION, POTENTIALLY BRINGING TROPICAL MOISTURE
AND A RISK OF HEAVY PRECIPITATION INTO PARTS OF THE SOUTHWESTERN CONUS.
HAZARDS
HIGH RISK OF EXTREME HEAT ACROSS PORTIONS OF THE NORTHERN PLAINS AND UPPER
MISSISSIPPI VALLEY, THU, JUL 16.
MODERATE RISK OF EXTREME HEAT ACROSS PORTIONS OF THE CALIFORNIA CENTRAL VALLEY,
SOUTHWEST, GREAT BASIN, AND THE ROCKIES, THU-SAT, JUL 16-18.
MODERATE RISK OF EXTREME HEAT ACROSS THE GREAT PLAINS, MISSISSIPPI VALLEY,
SOUTHEAST, AND CAROLINAS, THU-SAT, JUL 16-18.
SLIGHT RISK OF EXTREME HEAT ACROSS MUCH OF THE WESTERN AND CENTRAL CONUS AS
WELL AS THE SOUTHEAST, OHIO AND TENNESSEE VALLEYS, GREAT LAKES, AND THE
SOUTHERN MID-ATLANTIC, THU-MON, JUL 16-20.
SLIGHT RISK OF HEAVY PRECIPITATION ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN
ROCKIES AND DESERT SOUTHWEST, THU-MON, JUL 16-20.
DETAILED SUMMARY
FOR SATURDAY JULY 11 - WEDNESDAY JULY 15:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY JULY 16 - WEDNESDAY JULY 22: MULTIPLE MODEL ENSEMBLES DEPICT
ANOMALOUS RIDGING DEVELOPING ACROSS THE WESTERN AND CENTRAL CONUS AROUND THE
MIDDLE OF WEEK-1 AND PERSISTING INTO WEEK-2. WHILE THE RIDGE IS PREDICTED TO
PEAK IN STRENGTH PRIOR TO THE START OF WEEK-2, THE 0Z ECMWF AND GEFS ENSEMBLES
STILL DEPICT A 595-596 DM RIDGE CENTER AT THE OUTSET OF WEEK-2. MODELS ARE IN
NO BETTER AGREEMENT COMPARED TO YESTERDAY REGARDING THE MID-LEVEL PATTERN
PROGRESSION OVER THE CONUS, WITH THE 0Z ECMWF ENSEMBLE CONTINUING TO DEPICT A
MORE EASTWARD ORIENTATION OF THE RIDGE, WITH ENHANCED POSITIVE 500-HPA HEIGHT
ANOMALIES (GREATER THAN 60 METERS) OVER PORTIONS OF THE MIDWEST. CONVERSELY,
THE 0Z GEFS DEPICTS MORE AMPLIFIED TROUGHING DEVELOPING OVER THE NORTHEASTERN
U.S. WHICH RESULTS IN A QUICKER RETROGRESSION OF THE RIDGING OVER THE WESTERN
CONUS, AND INCREASING NORTHWESTERLY MID-LEVEL FLOW INTO THE UPPER MIDWEST AND
OHIO VALLEY FAVORING RELATIVELY COOLER TEMPERATURES. THE FORECAST LEANS MORE ON
THE ECMWF DUE TO RECENT MODEL SKILL IN PERSISTING THE PREVIOUS HEAT WAVE ACROSS
THE EASTERN U.S.
AT THE START OF THE PERIOD, EXTREME HEAT IS FORECAST ACROSS MUCH OF THE GREAT
PLAINS AND MISSISSIPPI VALLEY UNDERNEATH THE AFOREMENTIONED RIDGE AXIS. IN
ADDITION, ENHANCED SUBTROPICAL RIDGING COMBINED WITH ABOVE-NORMAL SEA SURFACE
TEMPERATURES OVER THE EASTERN GULF OF AMERICA FAVOR EXTREME HEAT ACROSS
PORTIONS OF THE SOUTHEAST AND FLORIDA. THE ECMWF ENSEMBLE INDICATES
TEMPERATURES IN THE UPPER 80S TO LOW 90S DEG F ACROSS THE GREAT LAKES AND OHIO
VALLEY EARLY IN WEEK-2, WITH THE ECMWF PROBABILISTIC EXTREMES TOOL (PET)
DEPICTING AT LEAST A 40 PERCENT CHANCE MAXIMUM TEMPERATURES EXCEED THE 85TH
CLIMATOLOGICAL PERCENTILE ACROSS THE UPPER MIDWEST. HOWEVER, THE GEFS IS
SUBSTANTIALLY COOLER OVER THESE AREAS, AS A FRONTAL SYSTEM MOVES THROUGH THE
REGION TIED TO TROUGHING AMPLIFYING ACROSS THE NORTHEAST. THE GEFS SOLUTION
WOULD FAVOR THE LARGEST EXTREME HEAT RISK SHIFTING FARTHER TO THE WEST OVER THE
GREAT PLAINS AND WESTERN CONUS. A HIGH RISK OF EXTREME HEAT IS POSTED ACROSS
PORTIONS OF THE NORTHERN PLAINS AND THE ADJACENT AREAS OF THE UPPER MISSISSIPPI
VALLEY, JUL 16, WHERE THE GEFS AND ECMWF ARE IN BETTER ALIGNMENT AND SKILL
WEIGHTED HEAT RISK GUIDANCE INDICATES PROBABILITIES GREATER THAN 50 PERCENT FOR
HEAT INDEX VALUES TO EXCEED 100 DEG F TIED TO HIGHER THAN NORMAL HUMIDITY
FORECAST OVER THE REGION. THESE NORTHERN AREAS HAVE LOWER THRESHOLDS FOR
EXTREME HEAT COMPARED TO FARTHER SOUTH, JUSTIFYING THE HIGH RISK. A MODERATE
RISK FOR EXTREME HEAT IS POSTED ACROSS MUCH OF THE GREAT PLAINS, MISSISSIPPI
VALLEY, AND SOUTHEAST, JUL 16-18, WITH HEAT INDEX VALUES POTENTIALLY ABOVE 105
DEG F ACROSS THE CENTRAL AND SOUTHERN PLAINS, AND ALONG THE GULF COAST AND
SOUTHEAST. THE NATIONAL BLEND OF MODELS (NBM) DEPICTS RECORD HIGH MINIMUM
TEMPERATURES ACROSS PARTS OF THE SOUTHEAST INTO FLORIDA, INDICATING LITTLE
OVERNIGHT RELIEF FROM THE HEAT. THE SLIGHT RISK OF EXTREME HEAT IS EXTENDED
FARTHER TO THE EAST ACROSS THE GREAT LAKES AND OHIO VALLEY, JUL 16-20,
CONSISTENT WITH THE ECMWF, BUT WITH CONFIDENCE DECREASED SOMEWHAT DUE TO THE
GEFS DEPICTION.
ELEVATED CHANCES OF EXTREME HEAT ARE ALSO FORECAST ACROSS MUCH OF THE WESTERN
CONUS, ALTHOUGH THERE IS ALSO UNCERTAINTY AS THE GEFS IS QUICKER, AND BOTH THE
GEFS AND ECMWF BEGIN TO WEAKEN THE RIDGE AMPLITUDE BY THE SECOND HALF OF THE
PERIOD. THERE IS A DECENT SIGNAL IN THE UNCALIBRATED 0Z GEFS AND ECMWF
ENSEMBLES FOR TEMPERATURES ABOVE 100 DEG F ACROSS LOW ELEVATION AREAS OF THE
GREAT BASIN AND ROCKIES, AND POSSIBLY ABOVE 105 DEG F ACROSS THE CALIFORNIA
CENTRAL VALLEY SUPPORTING A MODERATE RISK FOR EXTREME HEAT, JUL 16-18. A SLIGHT
RISK FOR EXTREME HEAT REMAINS FOR THE DESERT SOUTHWEST DUE TO THE POTENTIAL FOR
MONSOON MOISTURE TO LOWER TEMPERATURES, ALONG WITH THE WILLAMETTE VALLEY OF
OREGON WHERE UNCALIBRATED TOOLS DEPICT SOME POTENTIAL (20-40 PERCENT CHANCE)
FOR TEMPERATURES ABOVE 90 DEG F.
HIGH TEMPERATURES OVER THE SOUTHWEST ARE LIKELY TO INDUCE THERMAL SURFACE LOW
PRESSURE WHICH COMBINED WITH THE RIDGE AXIS BECOMING POSITIONED NEAR THE FOUR
CORNERS, SHOULD PULL TROPICAL MOISTURE NORTHWARD INTO THE REGION, KICKING OFF
THE SOUTHWEST MONSOON SEASON. THE ECMWF PET DEPICTS 40-60 PERCENT CHANCES FOR
RAINFALL EXCEEDING THE 85TH CLIMATOLOGICAL PERCENTILE AND ONE-HALF INCH EARLY
IN THE PERIOD, DECREASING LATER IN WEEK-2. PROBABILITIES IN THE GEFS PET ARE
GENERALLY LOW, BUT STILL INDICATE AN ENHANCED SIGNAL (AT LEAST 20 PERCENT
CHANCE) THROUGH THE MIDDLE OF THE PERIOD. THEREFORE, A SLIGHT RISK OF HEAVY
PRECIPITATION IS POSTED FOR MUCH OF THE CENTRAL AND SOUTHERN ROCKIES AND DESERT
SOUTHWEST, JUL 16-20, CONSISTENT WITH THE PETS, AND THE UNCALIBRATED ECMWF AND
GEFS WHICH DEPICT ENHANCED PRECIPITATION EXTENDING NORTHWARD INTO UTAH AND
COLORADO. THE SIGNAL IS SOMEWHAT WEAKER TOWARD THE END OF WEEK-2, TIED TO SLOW
WEAKENING OF THE MID-LEVEL RIDGE. IN ADDITION TO THE HEAVY RAIN THREAT,
MONSOONAL THUNDERSTORMS CAN ALSO PRODUCE DRY LIGHTNING, RESULTING IN INCREASED
WILDFIRE RISK.
FORECASTER: THOMAS COLLOW
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