581
FXUS21 KWNC 071842
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 07 2025
SYNOPSIS: MID-LEVEL HIGH PRESSURE, INITIALLY OVER THE NORTHEAST, IS FORECAST TO
SHIFT WESTWARD TO THE NORTH-CENTRAL CONTIGUOUS U.S. (CONUS) EARLY IN WEEK-2.
ALTHOUGH 7-DAY TEMPERATURES (AUGUST 15-21) ARE FAVORED TO AVERAGE ABOVE-NORMAL
FOR MUCH OF THE LOWER 48 STATES, CHANCES FOR ANY WIDESPREAD MAJOR HEAT WAVES
BEGIN TO DIMINISH HEADING INTO THE LATTER HALF OF THE MONTH. AN ENHANCED
MONSOON IS EXPECTED ACROSS THE DESERT SOUTHWEST FROM AUGUST 15 TO 19. THE
TROPICS IN THE ATLANTIC BASIN ARE BECOMING MORE ACTIVE FOR TROPICAL CYCLONE
DEVELOPMENT AND WILL BE CLOSELY MONITORED IN THE WEEKS AHEAD.
HAZARDS
SLIGHT RISK OF EXTREME HEAT FOR PARTS OF THE CENTRAL U.S., FRI-TUE, AUG 15-19.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE NORTHERN GREAT PLAINS AND
UPPER MISSISSIPPI VALLEY, FRI-SUN, AUG 15-17.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE SOUTHWEST, FRI-TUE, AUG 15-19.
SLIGHT RISK OF HEAVY PRECIPITATION FOR SOUTHEASTERN ALASKA, FRI, AUG 15.
DETAILED SUMMARY
FOR SUNDAY AUGUST 10 - THURSDAY AUGUST 14:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR FRIDAY AUGUST 15 - THURSDAY AUGUST 21: THE GEFS AND ECENS ARE IN GOOD
AGREEMENT, INDICATING ANOMALOUS 500-HPA RIDGING BECOMING CENTERED OVER THE
NORTH-CENTRAL CONUS DURING WEEK-2. THESE ENSEMBLE MEANS DEPICT 500-HPA HEIGHTS
RANGING FROM 588 TO 594 DM ACROSS THE CENTRAL TO SOUTHERN GREAT PLAINS AND
MIDDLE TO LOWER MISSISSIPPI VALLEY, WHICH ELEVATES THE RISK OF EXTREME HEAT.
BASED ON GOOD MODEL AGREEMENT AND CONSISTENCY ON THE LONGWAVE PATTERN, A SLIGHT
UPWARD TREND IN THE ECMWF PROBABILISTIC EXTREMES TOOL (PET), AND UNCALIBRATED
GEFS AND ECENS MAXIMUM TEMPERATURES, A SLIGHT RISK OF EXTREME HEAT (AUGUST
15-19) IS POSTED FOR PARTS OF THE GREAT PLAINS EAST TO THE MISSISSIPPI VALLEY.
THIS OUTLINED RISK AREA IS ALSO CONSISTENT WITH THE CALIBRATED ECMWF HEAT INDEX
TOOL WHICH HAS AT LEAST A 20 PERCENT CHANCE OF HEAT INDEX VALUES EXCEEDING 100
(105) DEGREES F FOR THE HUMID AREAS OF SOUTH DAKOTA AND NEBRASKA (KANSAS,
OKLAHOMA, ARKANSAS, AND MISSOURI). ALTHOUGH ABOVE-NORMAL TEMPERATURES ARE
FAVORED TO CONTINUE ACROSS THE NORTHEAST AND MID-ATLANTIC THROUGHOUT WEEK-2,
THE MODEL GUIDANCE HAS THE HOTTEST TEMPERATURES PRIOR TO THE START OF WEEK-2.
HEADING INTO WEEK-2, THE ECENS FAVORS A SHORTWAVE TROUGH PROGRESSING OVERTOP
THE BUILDING RIDGE ACROSS THE NORTH-CENTRAL CONUS. ALTHOUGH TIMING OF
INDIVIDUAL SHORTWAVE TROUGHS IS HIGHLY UNCERTAIN AT THIS TIME LEAD, PATTERN
RECOGNITION AND THE UNCALIBRATED ECENS PROBABILITIES FOR MORE THAN ONE INCH OF
PRECIPITATION SUPPORT A SLIGHT RISK OF HEAVY PRECIPITATION ACROSS THE EASTERN
DAKOTAS AND UPPER MISSISSIPPI VALLEY FROM AUG 15 TO 17. GIVEN THE ANTECEDENT
WETNESS FOR MUCH OF THOSE AREAS, ANY HEAVY RAINFALL COULD LEAD TO FLASH
FLOODING.
AS THE 500-HPA RIDGE AXIS SHIFTS NORTH TOWARDS THE FOUR CORNERS REGION, AN
ENHANCED MONSOON IS EXPECTED TO RESUME ACROSS THE SOUTHWEST BY WEEK-2, WHICH IS
CONSISTENT WITH DAYS FOLLOWING A HEAT WAVE. BASED ON THE PREFERRED ECMWF
PROBABILISTIC EXTREMES TOOL (AT LEAST A 20 PERCENT CHANCE OF 3-DAY AMOUNTS
EXCEEDING THE 85TH PERCENTILE AND 0.5 INCHES), A SLIGHT RISK OF HEAVY
PRECIPITATION IS POSTED FOR THIS REGION. THE SLIGHT RISK OF HEAVY PRECIPITATION
IS DISCONTINUED AFTER AUGUST 19TH AS THE ECENS DEPICTS 500-HPA HEIGHT ANOMALIES
INCREASING TO +30 METERS OR MORE, WHICH WOULD SUPPRESS CONVECTION. ANY HEAVY
RAINFALL IN A SHORT PERIOD OF TIME COULD TRIGGER FLASH FLOODING WITH BURN SCAR
AREAS BEING THE MOST VULNERABLE.
THE NATIONAL HURRICANE CENTER IS MONITORING A TROPICAL WAVE ACROSS THE EASTERN
ATLANTIC AND STATES THAT THIS WAVE HAS A 60 PERCENT CHANCE OF TROPICAL CYCLONE
(TC) DEVELOPMENT (AS OF 2PM EDT ON AUG 7) DURING THE NEXT WEEK. MODEL CONSENSUS
FAVORS THIS POTENTIAL TC EVENTUALLY TURNING NORTH AND REMAINING WEAK. WITH THE
MADDEN-JULIAN OSCILLATION (MJO) FORECAST TO PROPAGATE EAST TO THE INDIAN OCEAN
DURING THE NEXT TWO WEEKS, THE LARGE-SCALE ENVIRONMENT IS EXPECTED TO REMAIN
FAVORABLE FOR TC GENESIS ACROSS THE MAIN DEVELOPMENT REGION (MDR) OF THE
TROPICAL ATLANTIC. THE LATEST MODEL RUNS ARE KEYING ON ANOTHER TROPICAL WAVE
ENTERING THE EASTERN ATLANTIC AND MANY GEFS AND ECENS FAVOR THIS BECOMING A TC
LATER NEXT WEEK ACROSS THE MDR. FUTURE MODEL RUNS WILL BE CLOSELY MONITORED.
30-DAY PRECIPITATION DEFICITS EXCEED 2 INCHES ACROSS PARTS OF THE SOUTHERN
GREAT PLAINS, OZARKS, LOWER MISSISSIPPI VALLEY, AND TENNESSEE VALLEY. WITH
ANOTHER DRY WEEK AND TYPICAL AUGUST HEAT, SOIL MOISTURE WILL CONTINUE TO DRY
OUT MAKING THESE AREAS SUSCEPTIBLE TO RAPID ONSET DROUGHT (ROD) IN THE NEXT FEW
WEEKS. HOWEVER, FORECAST CONFIDENCE IS TOO LOW TO POST A ROD RISK ON THE MAP AT
THIS TIME WITH SOIL MOISTURE JUST BEGINNING TO DRY OUT AND THE WEEK-2
PRECIPITATION OUTLOOK LEANING TOWARDS NEAR OR ABOVE-NORMAL PRECIPITATION.
A BROAD 500-HPA TROUGH IS FORECAST TO PERSIST OVER ALASKA THROUGH MID-AUGUST
WHICH FAVORS A COOL, WET PATTERN FOR MUCH OF THE STATE. ALTHOUGH THE 24-HOUR
ENSEMBLE MEAN PRECIPITATION AMOUNTS AND PETS HAVE ONLY A MARGINAL SIGNAL FOR
HEAVY PRECIPITATION, A SLIGHT RISK FOR HEAVY PRECIPITATION IS POSTED FOR
SOUTHEASTERN ALASKA ON AUGUST 15. GIVEN THE COLDER-THAN-NORMAL TEMPERATURES,
PERIODS OF SNOW ARE EXPECTED TO AFFECT THE BROOKS RANGE.
FORECASTER: BRAD PUGH
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