314
FXUS21 KWNC 031837
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 03 2026
SYNOPSIS: MID-LEVEL HIGH PRESSURE IS FORECAST TO STRENGTHEN OVER THE SOUTHERN
TO CENTRAL GREAT PLAINS AND LOWER TO MIDDLE MISSISSIPPI VALLEY DURING
MID-AUGUST WHICH WOULD INCREASE THE CHANCE OF EXTREME HEAT. ANTECEDENT DRYNESS
ALONG WITH THE LIKELIHOOD OF ABOVE-NORMAL TEMPERATURES AND BELOW-NORMAL
PRECIPITATION DURING THE NEXT TWO WEEKS SUPPORTS AN ENHANCED RISK FOR THE RAPID
ONSET OF DROUGHT TO PARTS OF THE CENTRAL TO SOUTHERN GREAT PLAINS AND OZARKS
REGION. AN ENHANCED MONSOON IS FORECAST BY AUGUST 10TH WITH AN INCREASED CHANCE
OF LOCALLY HEAVY PRECIPITATION AND FLASH FLOODING FROM THE DESERT SOUTHWEST
NORTH TO THE CENTRAL ROCKIES.
HAZARDS
MODERATE RISK OF EXTREME HEAT FOR PARTS OF THE CENTRAL ROCKIES, AND CENTRAL TO
SOUTHERN HIGH PLAINS, TUE-WED, AUG 11-12.
MODERATE RISK OF EXTREME HEAT FOR MUCH OF THE CENTRAL TO SOUTHERN GREAT PLAINS
AND MIDDLE TO LOWER MISSISSIPPI VALLEY, TUE-MON, AUG 11-17.
SLIGHT RISK OF EXTREME HEAT FOR MOST OF THE CONUS EXCLUDING PORTIONS OF THE
NORTHERN, WESTERN, SOUTHWESTERN CONUS, AND APPALACHIANS, TUE-MON, AUG 11-17.
MODERATE RISK OF HEAVY PRECIPITATION FOR PARTS OF THE SOUTHWEST, TUE-FRI, AUG
11-14.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE DESERT SOUTHWEST AND FOUR CORNERS
REGION, TUE-MON, AUG 11-17.
FLASH FLOODING POSSIBLE FOR PARTS OF THE SOUTHWEST.
INCREASED RISK FOR RAPID ONSET DROUGHT (ROD) ACROSS PARTS OF THE CENTRAL TO
SOUTHERN GREAT PLAINS AND OZARKS REGION.
DETAILED SUMMARY
FOR THURSDAY AUGUST 06 - MONDAY AUGUST 10:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY AUGUST 11 - MONDAY AUGUST 17: THE GEFS AND ECENS REMAIN CONSISTENT
AND IN GOOD AGREEMENT THAT A BROAD AND MODERATELY STRONG 500-HPA RIDGE PERSISTS
OVER THE SOUTHERN TWO-THIRDS OF THE CONTIGUOUS U.S. (CONUS) THROUGH MID-AUGUST.
COMPARED TO THE BEGINNING OF THE MONTH, THESE ENSEMBLE MEANS DEPICT A SLIGHTLY
WEAKER RIDGE (500-HPA HEIGHTS BELOW 597 DM) BUT THERE REMAINS EITHER A SLIGHT
OR MODERATE RISK OF EXTREME HEAT FOR MUCH OF THE LOWER 48 STATES FROM AUG 11 TO
17. THE 500-HPA RIDGE IS FORECAST TO WEAKEN (STRENGTHEN) OVER THE WESTERN
(CENTRAL AND SOUTHEASTERN) CONUS FROM EARLY TO MID-AUGUST. A MODERATE RISK OF
EXTREME HEAT, VALID AUG 11 AND 12, IS POSTED FOR THE CENTRAL ROCKIES, AND
CENTRAL TO SOUTHERN HIGH PLAINS WHERE THE NWS HEATRISK TOOL INDICATES MORE THAN
A 40 PERCENT CHANCE OF REACHING THE MAJOR HEATRISK CATEGORY. ALSO, A CONSENSUS
OF THE GEFS AND ECENS PROBABILISTIC EXTREMES TOOLS (PETS) GENERALLY DEPICT THAT
MAXIMUM TEMPERATURES HAVE AT LEAST A 40 PERCENT CHANCE OF EXCEEDING THE 85TH
PERCENTILE. THE STRENGTHENING RIDGE ALOFT, WITH 500-HPA HEIGHTS INCREASING TO
NEAR OR EXCEEDING 594 DM, SUPPORTS A MODERATE RISK OF EXTREME HEAT FROM THE
CENTRAL AND SOUTHERN GREAT PLAINS EAST TO THE MIDDLE AND LOWER MISSISSIPPI
VALLEY FOR THE ENTIRE WEEK-2 PERIOD. ENSEMBLE MEANS INDICATE TEMPERATURE
ANOMALIES OF 5-10+ DEG F ABOVE NORMAL IN THE OUTLINED MODERATE RISK AREA ACROSS
THE SOUTH-CENTRAL CONUS. MAXIMUM HEAT INDEX VALUES ARE FORECAST TO RANGE FROM
100-105 DEG F IN THE CENTRAL GREAT PLAINS TO 105-110 DEG F IN THE SOUTHERN
GREAT PLAINS AND LOWER MISSISSIPPI VALLEY. THE GEFS WOULD ALSO SUPPORT A
MODERATE RISK OF EXTREME HEAT FOR THE COASTAL PLAIN OF THE SOUTHEAST. HOWEVER,
THE ECENS AND CMCE ARE COOLER MODEL SOLUTIONS AND WITH AN AMPLIFIED 500-HPA
TROUGH NEARBY OVER THE NORTHEAST, FORECAST CONFIDENCE IS NOT HIGH ENOUGH TO
DESIGNATE A MODERATE RISK FOR THE SOUTHEAST AT THIS TIME. THE PERSISTENCE OF
THE ANOMALOUS 500-HPA RIDGE SUPPORTS A SLIGHT RISK OF EXTREME HEAT FOR A
MAJORITY OF THE CONUS THROUGH THE END OF WEEK-2, AUG 17. ANOMALOUSLY WARM
TEMPERATURES AND DRIER-THAN-NORMAL CONDITIONS ARE EXPECTED TO MAINTAIN AN
ELEVATED WILDFIRE DANGER ACROSS THE NORTHERN INTERMOUNTAIN WEST THROUGH
MID-AUGUST.
THE ADJUSTMENTS MADE TODAY TO THE EXTREME HEAT AREAS COMPARED TO YESTERDAY
INCLUDE THE REMOVAL OF THE SLIGHT RISK AREA MOSTLY OUT OF WASHINGTON STATE,
CALIFORNIA, AND AT LEAST WESTERN OREGON. THE MODERATE SHAPE THAT WAS OVER THE
WEST YESTERDAY WAS TRIMMED BACK TO NEAR THE CONTINENTAL DIVIDE. IN ADDITION,
THE SLIGHT RISK CONTOUR WAS EXPANDED NORTHWARD ACROSS THE CENTRAL CONUS TO
INCLUDE MOST OF THE DAKOTAS, MINNESOTA, AND WISCONSIN. THESE ADJUSTMENTS ARE
CONSISTENT WITH THE EXPECTED SHIFT OF THE STRONGEST HEAT SIGNALS FROM THE WEST
INTO THE CENTRAL CONUS, WITH THE MEAN POSITION OF THE MID-LEVEL RIDGE BEING
CENTERED OVER THE NORTHERN HIGH PLAINS.
THE ENSEMBLE MEAN SOLUTIONS REMAIN CONSISTENT THAT THE SUBTROPICAL RIDGE AXIS
BECOMES CENTERED OVER THE FOUR CORNERS REGION HEADING INTO WEEK-2, FAVORING A
ROBUST MONSOON. IN ADDITION, A WEAKENING RIDGE ALOFT SHOULD ALLOW FOR MORE
WIDESPREAD CONVECTION. THE PREDICTED 500-HPA HEIGHT PATTERN ALONG WITH 1 TO
3-DAY PRECIPITATION AMOUNTS FROM THE GEFS AND ECENS SUPPORT A MODERATE RISK OF
HEAVY PRECIPITATION FROM ARIZONA NORTHEASTWARD INTO SOUTHWESTERN COLORADO FROM
AUGUST 11 TO 14. ANY LOCALLY HEAVY RAINFALL COULD TRIGGER FLASH FLOODING,
ESPECIALLY IN BURN SCAR AREAS, AND A FLASH FLOODING POSSIBLE HAZARD COINCIDES
WITH THE MODERATE RISK OF HEAVY PRECIPITATION. BASED ON THE GEFS AND ECENS PETS
(> 20% CHANCE OF 3-DAY AMOUNTS EXCEEDING THE 85TH PERCENTILE), A SLIGHT RISK OF
HEAVY PRECIPITATION EXTENDS FROM THE DESERT SOUTHWEST NORTHEAST TO THE CENTRAL
ROCKIES AND GOES THROUGH AUG 17.
MULTI-MODEL ENSEMBLE MEANS AGREE THAT A 500-HPA TROUGH SHIFTS EAST NEAR THE
GREAT LAKES AT THE BEGINNING OF WEEK-2, WHICH COULD RESULT IN MESOSCALE
CONVECTIVE SYSTEMS (MCS) TRACKING SOUTHEASTWARD ACROSS THE MIDWEST. GIVEN THE
VERY HUMID AIRMASS, ANY MCS WILL BE CAPABLE OF PRODUCING FLASH FLOODING.
PATTERN RECOGNITION AND 1 TO 3-DAY PRECIPITATION AMOUNTS FROM THE GEFS AND
ECENS WERE USED AS GUIDES TO DEFINE THE SLIGHT RISK OF HEAVY PRECIPITATION,
VALID FROM AUGUST 11 TO 13.
A RAPID ONSET DROUGHT (ROD) RISK IS DESIGNATED FOR PARTS OF THE CENTRAL AND
SOUTHERN PLAINS ALONG WITH THE OZARKS REGION WHERE 30-DAY PRECIPITATION
DEFICITS ARE GREATER THAN 2 INCHES AND CONTINUED DRYNESS AND HEAT ARE FORECAST
THROUGH EARLY TO MID-AUGUST.
FORECASTER: ANTHONY ARTUSA
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