789
FXUS21 KWNC 251835
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 25 2026
SYNOPSIS: A PERSISTENT AREA OF STRONG MID-LEVEL HIGH PRESSURE OVER THE SOUTHERN
TIER OF THE CONTIGUOUS U.S. (CONUS) SUPPORTS ABOVE-NORMAL LATE SUMMERTIME
TEMPERATURES AND A CONTINUED RISK OF EXCESSIVE HEAT, WITH THE GREATEST RISK
FOCUSED OVER THE SOUTHERN PLAINS EARLY IN THE PERIOD BEFORE MID-LEVEL HIGH
PRESSURE GRADUALLY EASES WITH TIME. ENHANCED MOISTURE ADVECTION FAVORED OVER
THE SOUTHWESTERN CONUS TOWARDS THE LATER PART OF NEXT WEEK INCREASES CHANCES
FOR HEAVY PRECIPITATION ACROSS PARTS OF THE DESERT SOUTHWEST. THE ABNORMALLY
HOT AND DRY CONDITIONS OVER THE PAST FEW WEEKS ARE EXPECTED TO CONTINUE THROUGH
MUCH OF WEEK-2, SUPPORTING A RAPID ONSET DROUGHT (ROD) RISK FOR PORTIONS OF THE
CENTRAL AND SOUTHERN PLAINS, AND THE MIDDLE AND LOWER MISSISSIPPI VALLEY.
HAZARDS
HIGH RISK OF EXTREME HEAT FOR THE CENTRAL AND SOUTHERN PLAINS, AND PORTIONS OF
THE LOWER AND MIDDLE MISSISSIPPI VALLEY, WED, SEP 2.
MODERATE RISK OF EXTREME HEAT FOR THE PARTS OF THE DESERT SOUTHWEST, SOUTHERN
AND CENTRAL PLAINS, LOWER AND MIDDLE MISSISSIPPI VALLEY, AND SOME ADJACENT
AREAS, WED-THU, SEP 2-3.
SLIGHT RISK OF EXTREME HEAT FOR SOUTHERN PARTS OF CALIFORNIA, THE SOUTHERN
GREAT BASIN, ROCKIES, GREAT PLAINS, MISSISSIPPI, TENNESSEE, AND LOWER OHIO
VALLEYS, EASTERN GULF COAST REGION, AND SOUTHERN PORTIONS OF THE EASTERN
SEABOARD, WED-TUE, SEP 2-8.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF SOUTHERN ARIZONA AND SOUTHERN
NEW MEXICO, FRI-SUN, SEP 4-6.
RAPID ONSET DROUGHT (ROD) RISK FOR PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS,
THE LOWER MISSISSIPPI VALLEY AND ADJACENT AREAS.
DETAILED SUMMARY
FOR FRIDAY AUGUST 28 - TUESDAY SEPTEMBER 01:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY SEPTEMBER 02 - TUESDAY SEPTEMBER 08: OVER THE PAST WEEK OR SO,
DYNAMICAL MODELS CONTINUE TO FAVOR A FAIRLY STABLE 500-HPA HEIGHT PATTERN FOR
THE WEEK-2 PERIOD. THE MAIN MEAN HEIGHT FEATURES CONSIST OF ENHANCED
SUBTROPICAL RIDGING OVERSPREADING THE SOUTHERN TIER OF THE U.S. WITH AN
ANOMALOUS RIDGE AXIS EXTENDING NORTHWARD INTO CANADA, BOOKENDED BY A PAIR OF
MEAN TROUGHS OVER THE NORTHWESTERN AND NORTHEASTERN CONUS, ALL OF WHICH ARE
FAVORED TO PERSIST INTO EARLY SEPTEMBER. ACCOMPANYING THE STRONG SUBTROPICAL
RIDGING, THERE CONTINUES TO BE GOOD SUPPORT FOR THE CONTINUATION OF A LONG
DURATION LATE SUMMER HEAT WAVE, THOUGH BOTH THE GEFS AND ECMWF ENSEMBLES HAVE
BECOME SLIGHTLY LESS AMPLIFIED WITH THIS HEIGHT FEATURE OVER THE PAST SEVERAL
DAYS, RESULTING IN A SLIGHTLY DECREASED RISK OF EXTREME HEAT IN THE UPDATED
OUTLOOK. WHILE THE SUBTROPICAL RIDGE CENTER HAS BEEN SHOWN TO MEANDER, SHIFTING
ZONALLY BETWEEN THE LOWER FOUR CORNERS AND THE LOWER MISSISSIPPI VALLEY SINCE
LAST WEEK, MODELS ARE IN AGREEMENT WITH THE POSITION AND STRENGTH OF THE RIDGE
CENTER OVER THE SOUTHERN HIGH PLAINS BY THE OUTSET OF THE PERIOD, WHERE THE
GREATEST RISK OF EXTREME HEAT IS EXPECTED TO BE INITIALLY FOCUSED. OVER TIME,
THERE ARE LOWERING CHANCES FOR 500-HPA HEIGHTS EXCEEDING 594 DM RIDGE CENTER,
WITH A LARGE DISPERSION OF WEAK HEIGHT EXCEEDANCE SIGNALS THROUGHOUT THE
SOUTHERN TIER OF THE U.S.. AS A RESULT, THERE IS MORE UNCERTAINTY AS TO WHERE
THE RIDGE CENTER WILL MIGRATE NEXT, AND WHETHER THE HEAT EVENT WILL PERSIST
INTO AND BEYOND LABOR DAY WEEKEND.
UNDERNEATH THE SUBTROPICAL RIDGE CENTER, A HIGH RISK OF EXTREME HEAT IS POSTED
WITH COVERAGE NOW LIMITED FROM EASTERN NEW MEXICO EASTWARD INTO PORTIONS OF
OKLAHOMA AND TEXAS, AND ADJACENT PARTS OF THE CENTRAL PLAINS AND MISSISSIPPI
VALLEY. THIS HIGH RISK IS SUPPORTED BY CALIBRATED HEAT TOOLS INDICATING
ELEVATED CHANCES (>50%) FOR DAYTIME TEMPERATURES AND/OR HEAT INDEX VALUES
EXCEEDING THE 90TH CLIMATOLOGICAL PERCENTILE, ELEVATED MAXIMUM TEMPERATURE
SIGNALS IN PERCENTILE SPACE AMONG THE PROBABISITIC EXTREME TOOLS (PETS), AND
THE NATIONAL BLEND OF MODELS SHOWING A NUMBER OF LOCATIONS WITH DAYTIME HIGHS
NEARING AND/OR BREAKING DAILY RECORDS OVER THE SOUTHERN HIGH PLAINS. THE HIGH
RISK REMAINS VALID THROUGH SEP 2 BEFORE THE SAME NBM ANALYSIS SHOWS A REDUCTION
TO ZERO LOCATIONS, WHICH IS ALSO SUPPORTED BY 24-HOUR TEMPERATURE CHANGES IN
THE ECMWF AND GEFS ENSEMBLES DEPICTING A SLIGHT DAYTIME COOLING TREND OVER THE
HIGHLIGHTED HIGH RISK AREA BY THE MIDDLE OF NEXT WEEK. WITHIN THE HIGHLIGHTED
HIGH RISK AREA, DAYTIME TEMPERATURES ARE LIKELY TO EXCEED 100 DEG F IN MANY
LOCATIONS (EXCEPT FOR THE HIGHER ELEVATIONS), WITH HEAT INDEX VALUES POSSIBLY
EXCEEDING 110 DEG WHERE DEWPOINT TEMPERATURES ARE HIGHER. SURROUNDING THE HIGH
RISK AREA, A MODERATE RISK OF EXTREME HEAT REMAINS POSTED WHERE TEMPERATURE AND
HEAT TOOLS MAINTAIN LESSER, BUT INCREASED CHANCES FOR TEMPERATURES EXCEEDING
THE UPPER CLIMATOLOGICAL PERCENTILES THROUGH SEP 3. COVERAGE OF THE MODERATE
RISK AREA IS REMOVED OVER THE DESERT SOUTHWEST, AND ALONG THE RIO GRANDE VALLEY
AND GULF COAST BASED ON COOLER TEMPERATURES FAVORED IN THE REGION AND WHERE
THERE IS LESS SUPPORT FOR POSITIVE TEMPERATURE ANOMALIES EXCEEDING 5 DEG F IN
THE RAW MODEL TOOLS. A BROAD SLIGHT RISK AREA OF EXTREME HEAT REMAINS POSTED
ACROSS THE SOUTHERN TIER OF THE U.S, WITH COVERAGE ADDED OVER PARTS OF THE
TENNESSEE AND OHIO VALLEYS AND MID-ATLANTIC BASED ON AN UPTICK IN TEMPERATURE
SIGNALS IN THE LATEST TOOLS EARLY IN THE PERIOD. WHILE THE MID-LEVEL PATTERN
LOOKS TO BECOME MORE ZONAL LATE IN WEEK-2, THE SLIGHT RISK REMAINS VALID FOR
THE ENTIRETY OF WEEK-2 DUE TO PETS MAINTAINING INCREASED CHANCES FOR MAXIMUM
TEMPERATURES EXCEEDING THE 85TH PERCENTILE FOR MUCH OF THE SOUTHERN TIER.
THE PERSISTENT, ELEVATED CHANCES FOR EXTREME HEAT IS LIKELY BEING REINFORCED BY
FEEDBACK PROCESSES ASSOCIATED WITH RAPIDLY DRYING SOILS AND DROUGHT WITHIN MANY
OF THE HIGHLIGHTED REGIONS. THE HOT AND DRY CONDITIONS FAVORED ARE ALSO
EXPECTED TO ELEVATE THE RISK OF FIRE WEATHER CONDITIONS DURING THE PERIOD. IN
ADDITION, A RAPID ONSET DROUGHT (ROD) RISK IS DESIGNATED ACROSS PORTIONS OF THE
CENTRAL AND SOUTHERN PLAINS AND LOWER (AND PARTS OF THE MIDDLE) MISSISSIPPI
VALLEY. THIS AREA HAS REGISTERED 30- TO 45-DAY PRECIPITATION DEFICITS GREATER
THAN 2 INCHES BELOW NORMAL AND/OR UNDER HALF OF NORMAL, WITH LESS THAN AN INCH
EXPECTED DURING THE NEXT TWO WEEKS.
ACROSS THE EASTERN AND CENTRAL PACIFIC, THERE HAS BEEN PRONOUNCED UPTICK IN
TROPICAL ACTIVITY DURING THE PAST WEEK, WHERE THE NATIONAL HURRICANE CENTER
(NHC) IS CURRENTLY EYEING TREE ACTIVE TROPICAL CYCLONES (LALA, ISELLE, AND
JULIO), ALONG WITH FOUR WATCH AREAS FOR DEVELOPMENT IN THE TROPICAL WEATHER
OUTLOOK (TWO). ONE WATCH AREA CURRENTLY LOCATED NEAR 135E HAS 70% CHANCES OF
DEVELOPMENT (AS OF 11AM PDT) WHERE BOTH ENSEMBLES AND PROBABILISTIC TOOLS SHOW
THIS POTENTIAL SYSTEM TRACKING WESTWARD TO THE SOUTH OF HAWAII MUCH IN THE SAME
MANNER AS LALA AND MOKE. WHILE THERE IS AMPLE UNCERTAINTY ASSOCIATED WITH THIS
DISTURBANCE, HEAVY PRECIPITATION AND OTHER ADVERSE IMPACTS TO HAWAII CANNOT BE
RULED OUT DURING WEEK-2.
TWO OTHER WATCH AREAS IN THE TWO ARE LOCATED CLOSER TO MEXICO, AND REGARDLESS
OF FORMATION DURING THE NEXT WEEK, A LOW TRACKING NEAR THE GULF OF CALIFORNIA
MAY TRIGGER A SURGE EVENT AND BRING ENHANCED MOISTURE INTO THE DESERT
SOUTHWEST. WITH TROUGHING ALSO FAVORED TO PERSIST OVER THE WEST COAST TO HELP
PULL MOISTURE INTO THE SOUTHWESTERN CONUS EARLY IN WEEK-2, THE ECMWF ENSEMBLE
FAVORS AN INCREASE IN ANOMALOUS PRECIPITABLE WATER REFLECTIVE OF ENHANCED
MOISTURE ADVECTION FAVORABLE FOR LOCALLY HEAVY PRECIPITATION. WHILE TOOLS ARE
FAIRLY TENUOUS WITH A HEAVY PRECIPITATION POTENTIAL, THERE IS GROWING SUPPORT
IN THE RAW AND CALIBRATED ECMWF PET TOWARDS THE MIDDLE OF WEEK-2 WITH INCREASED
CHANCES FOR 3-DAY AMOUNTS EXCEEDING THE 85TH PERCENTILE. THEREFORE, A SLIGHT
RISK OF HEAVY PRECIPITATION IS POSTED FOR PORTIONS OF SOUTHERN ARIZONA AND NEW
MEXICO FOR SEP 4-6. EPISODES OF HIGH WINDS ARE ALSO POSSIBLE AT THE BASE AND
AHEAD OF THE TROUGH AXIS ACROSS PORTIONS OF THE WEST COAST. HOWEVER, NO
CORRESPONDING HIGH WIND HAZARDS ARE ISSUED DUE TO THE DEAMPLIFICATION OF THE
TROUGHING BY THE MIDDLE OF NEXT WEEK, AND A LACK OF SUPPORT IN THE TOOLS.
COLDER TEMPERATURES ARE PREDICTED FOR THE BROOKS RANGE IN NORTHERN ALASKA
DURING WEEK-2. THOUGH PRECIPITATION AMOUNTS ARE NOT EXPECTED TO REACH HAZARDOUS
CRITERIA, THE REGION MAY EXPERIENCE ITS FIRST SNOWFALL OF THE SEASON.
FORECASTER: NICK NOVELLA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page