559
FXUS21 KWNC 241838
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 24 2026
SYNOPSIS: MODELS CONTINUE TO FAVOR A LONG-DURATION EXTREME HEAT EVENT FROM THE
SOUTHERN TIER OF THE CONTIGUOUS U.S. (CONUS) NORTHWARD INTO THE CENTRAL PLAINS
AND THE MIDDLE MISSISSIPPI VALLEY. THE GREATEST RISK IS FOCUSED FROM THE
SOUTHERN AND CENTRAL HIGH PLAINS EASTWARD TO THE LOWER (AND PORTIONS OF THE
MIDDLE) MISSISSIPPI VALLEY, UNDER AMPLIFIED AND LONG-LIVED MID-LEVEL HIGH
PRESSURE. SOME AREAS MAY EXPERIENCE HEAT MORE TYPICAL OF MID-SUMMER INTO THE
FIRST WEEK OF SEPTEMBER. MEANWHILE, UNUSUALLY 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, LOWER AND
PORTIONS OF THE MIDDLE MISSISSIPPI VALLEY, TUE-WED, SEP 1-2.
MODERATE RISK OF EXTREME HEAT FOR THE DESERT SOUTHWEST, SOUTHERN ROCKIES,
SOUTHERN AND CENTRAL PLAINS, LOWER AND MIDDLE MISSISSIPPI VALLEY, AND SOME
ADJACENT AREAS, TUE-THU, SEP 1-3.
SLIGHT RISK OF EXTREME HEAT FOR SOUTHERN PORTIONS OF CALIFORNIA, THE SOUTHERN
GREAT BASIN,CENTRAL AND SOUTHERN ROCKIES,CENTRAL AND SOUTHERN PLAINS, MIDDLE
AND LOWER MISSISSIPPI, TENNESSEE, AND LOWER OHIO VALLEYS, EASTERN GULF COAST
REGION, AND SOUTHERN PORTIONS OF THE EASTERN SEABOARD, TUE-MON, SEP 1-7.
RAPID ONSET DROUGHT (ROD) RISK FOR PORTIONS OF THE CENTRAL AND SOUTHERN PLAINS,
THE LOWER MISSISSIPPI VALLEY AND ADJACENT AREAS.
DETAILED SUMMARY
FOR THURSDAY AUGUST 27 - MONDAY AUGUST 31:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY SEPTEMBER 01 - MONDAY SEPTEMBER 07: EARLY IN WEEK-2 THE 0Z ECENS,
0Z GEFS, AND 0Z CMCE SOLUTIONS PREDICT A MAXIMUM 500-HPA HEIGHT OF 593-594 DM
ASSOCIATED WITH THE SUBTROPICAL RIDGE IN THE VICINITY OF SOUTHERN NEW MEXICO.
THE GEFS AND ECENS SHOW STANDARDIZED 500-HPA HEIGHT ANOMALIES TOPPING OUT AT
1.0-1.5 STANDARD DEVIATIONS ABOVE CLIMATOLOGY ON DAYS 8-9, WHICH REPRESENTS
SOME WEAKENING COMPARED TO SEVERAL DAYS AGO. THIS IS CONSISTENT WITH A
LONG-DURATION, MAJOR HEAT WAVE OVER MUCH OF THE CENTRAL AND SOUTHERN CONUS
THROUGH AT LEAST THE FIRST HALF OF WEEK-2, AND PERHAPS WELL INTO EARLY
SEPTEMBER IN SOME AREAS. THE THREE ENSEMBLE MEAN MODELS DEPICT A SLIGHTLY
ANOMALOUS MID-LEVEL TROUGH NEAR THE WEST COAST, HELPING TO TEMPORARILY DISPLACE
THE WESTERN PORTION OF THE SUBTROPICAL RIDGE SLIGHTLY TOWARDS THE EAST. THE
MID-LEVEL RIDGE IS BOOKENDED BY A PAIR OF MEAN TROUGHS NEAR THE WEST COAST AND
OVER THE NORTHEASTERN CONUS. TOWARDS THE END OF THE WEEK-2 OUTLOOK PERIOD, THE
FLOW PATTERN IS PREDICTED TO DEAMPLIFY SIGNIFICANTLY.
THE NATIONAL BLEND OF MODELS (NBM) DEPICTS 2 STATIONS WITH NEAR-RECORD OR
RECORD-BREAKING DAYTIME HIGH TEMPERATURES IN THE SOUTHERN HIGH PLAINS ON DAY 8
(SEP 1), DECREASING TO ZERO STATIONS BY DAY 10 (SEP 3). THIS DOWNWARD TREND
CONTINUES TO SUPPORT THE IDEA OF A SLIGHT BREAK IN THE EXTREME HEAT ACROSS THE
REGION, THOUGH IT WILL LIKELY STILL BE VERY HOT.
UNDERNEATH THE AMPLIFIED RIDGE, A HIGH RISK (GREATER THAN 60% CHANCE) OF
EXTREME HEAT REMAINS POSTED EARLY IN WEEK-2 (TUE-WED, SEP 1-2) FROM THE
SOUTHERN PLAINS AND SOUTHERN HALF OF KANSAS EASTWARD INTO THE LOWER (AND PARTS
OF THE MIDDLE) MISSISSIPPI VALLEY. THE ECENS AND GEFS PROBABILITY OF EXTREMES
TOOLS (PET) DEPICT SLIGHTLY REDUCED CHANCES (COMPARED TO SEVERAL DAYS AGO) OF
MAXIMUM TEMPERATURES EXCEEDING THE 85TH HISTORICAL PERCENTILE ACROSS THE
SOUTHWESTERN CONUS EARLY IN WEEK-2, WITH THE GEFS PET BEING SLIGHTLY MORE
EXTENSIVE WITH ITS HEAT COVERAGE COMPARED TO THE ECENS, AS HAS BEEN THE CASE
FOR MUCH OF THIS SUMMER. THE EASTERN PORTION OF THE HIGH RISK AREA COVERING
MUCH OF THE MISSISSIPPI VALLEY, IS LARGELY BASED ON THE EXPECTATION THAT DEW
POINTS WILL ELEVATE HEAT INDEX VALUES CONSIDERABLY ABOVE ACTUAL AIR
TEMPERATURES. A MODERATE RISK (40-60% CHANCE) OF EXTREME HEAT IS POSTED ACROSS
A LARGER AREA SURROUNDING THE HIGH RISK AREA, CONTINUING WESTWARD ACROSS THE
DESERT SOUTHWEST, AND IS VALID FOR ONE ADDITIONAL DAY (TUE-THU, SEP 1-3). A
SLIGHT RISK (20-40% CHANCE) OF EXTREME HEAT IS EXTENDED FOR THE DURATION OF
WEEK-2 (THROUGH MON SEP 7) ACROSS A LARGE PART OF THE CENTRAL AND SOUTHERN
CONUS. WITH TEMPERATURES IN THE MID-ATLANTIC REGION FORECAST TO FLUCTUATE
DURING THE PERIOD, IT WAS DECIDED NOT TO BRING THE SLIGHT RISK AREA ANY FARTHER
NORTH THAN SOUTHEASTERN VIRGINIA. THE SLIGHT, MODERATE, AND HIGH RISK AREAS OF
FAVORED EXTREME HEAT ARE LARGELY BASED ON A SUBJECTIVE CONSENSUS OF OBJECTIVE
TOOLS SUCH AS THE SKILL WEIGHTED AND CALIBRATED (AND RAW) HYBRID FORECAST
BETWEEN THE GEFS AND THE ECENS, SKILL-WEIGHTED AND BIAS-CORRECTED HYBRID
FORECAST (USING PROBABILITY OF EXCEEDANCE THRESHOLDS OF 105 DEG F AND 110 DEG
F, DAILY MAX UNCALIBRATED 0Z ECENS/GEFS/CMCE 2-METER TEMPERATURES AND
ANOMALIES, AND THE PROBABILISTIC EXTREMES TOOL (PET) TEMPERATURE GUIDANCE FROM
THE THREE ENSEMBLE MEANS.
THE ECENS IS MORE BULLISH TODAY RELATIVE TO THE GEFS ON EXPANDING THE HEAT INTO
THE OHIO VALLEY DURING WEEK-2. IF THE ECENS AND/OR THE GEFS SUPPORTS THIS
EXPANSION OF HEAT ASSOCIATED WITH THE MID-LEVEL RIDGE TOMORROW, THE HAZARDOUS
TEMPERATURE MAP MAY BE ADJUSTED TO REFLECT THIS DEVELOPMENT.
THE EPISODE OF EXTREME HEAT IS BEING EXACERBATED 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. THE POSSIBLE EXCEPTIONS INCLUDE SOUTHEASTERN LOUISIANA AND
SOUTHERN MISSISSIPPI, WHERE UP TO 3 INCHES OF RAIN IS PREDICTED. THIS AMOUNT OF
PRECIPITATION WOULD BE ENOUGH TO OVERCOME 2-INCH DEFICITS, PLUS TAKE INTO
ACCOUNT ONE WEEK OF CLIMATOLOGICAL RAINFALL. THE ROD SHAPE WAS TRIMMED BACK
ACCORDINGLY TO REFLECT THESE PRECIPITATION FORECASTS IN THE MISSISSIPPI DELTA
REGION. NEARLY ALL OF THIS ROD AREA IS WITHIN THE MODERATE AND HIGH RISK AREAS
OF EXTREME HEAT, AND THE RESULTING INCREASE IN EVAPOTRANSPIRATION RATES ARE
LIKELY TO ACCELERATE SURFACE MOISTURE DEPLETION.
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: ANTHONY ARTUSA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page