264
FXUS21 KWNC 061825
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 06 2025
SYNOPSIS: BROAD MID-LEVEL HIGH PRESSURE SUPPORTS AN INCREASED CHANCE OF
ABOVE-NORMAL TEMPERATURES FOR A MAJORITY OF THE CONTIGUOUS U.S. (CONUS) DURING
MID-AUGUST. DESPITE THE LIKELIHOOD OF ANOMALOUS WARMTH, 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 14 TO 20. 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-WED, AUG 15-20.
SLIGHT RISK OF HEAVY PRECIPITATION FOR THE SOUTHWEST, THU-WED, AUG 14-20.
SLIGHT RISK OF HEAVY PRECIPITATION FOR SOUTHEASTERN ALASKA, THU, AUG 14.
DETAILED SUMMARY
FOR SATURDAY AUGUST 09 - WEDNESDAY AUGUST 13:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY AUGUST 14 - WEDNESDAY AUGUST 20: BEGINNING ON AUGUST 15, THE
STRONG MID-LEVEL RIDGE INITIALLY CENTERED OVER EASTERN CANADA AND THE
NORTHEASTERN CONUS IS FAVORED TO SHIFT WESTWARD WITH 500-HPA HEIGHTS RISING
OVER THE NORTH-CENTRAL CONUS. THE GEFS DEPICTS A MORE RAPID RISE IN 500-HPA
HEIGHTS WITH DAILY HEIGHT ANOMALIES REACHING +60 METERS ACROSS THE NORTHERN
GREAT PLAINS AND UPPER MISSISSIPPI VALLEY BY AUGUST 17TH. IN ADDITION, THE
UNCALIBRATED GEFS IS RUNNING 5 TO 10 DEGREES F WARMER ACROSS THE NORTHERN AND
CENTRAL GREAT PLAINS COMPARED TO THE ECENS. THE WARMER GEFS MODEL SOLUTION
SEEMS TO BE RELATED TO ITS DRIER FORECAST FOR THESE AREAS. THE SLIGHTLY COOLER
ECMWF MODEL GUIDANCE WAS PREFERRED ACROSS THE NORTH-CENTRAL CONUS DUE TO HIGHER
SOIL MOISTURE FOR MANY AREAS AND AN INCREASED CHANCE OF MESOSCALE CONVECTIVE
SYSTEMS AFFECTING THAT REGION. BASED ON THE CALIBRATED ECMWF MODEL HAVING MORE
THAN A 20 PERCENT CHANCE OF HEAT INDEX VALUES EXCEEDING THE 90TH PERCENTILE AND
REACHING HEAT ADVISORY THRESHOLDS, A SLIGHT RISK OF EXTREME HEAT (AUGUST 15-20)
WAS MAINTAINED FOR PORTIONS OF THE GREAT PLAINS EAST TO THE MIDDLE AND LOWER
MISSISSIPPI VALLEY. WITHIN THIS SLIGHT RISK AREA, THE CALIBRATED ECMWF MODEL
INDICATES AT LEAST A 20 PERCENT CHANCE OF HEAT INDEX VALUES EXCEEDING 100 DEG
F AS FAR NORTH AS SOUTH DAKOTA.
ALTHOUGH NEAR TO ABOVE-NORMAL TEMPERATURES ARE FORECAST TO CONTINUE ACROSS THE
NORTHEAST THROUGHOUT WEEK-2, A COLD FRONTAL PASSAGE ON DAY 7 OR 8 IS EXPECTED
TO END THE RISK OF EXTREME HEAT. UNCALIBRATED MODEL RUNS GENERALLY HAVE THE
HOTTEST MAXIMUM TEMPERATURES, FROM AUG 14 TO 20, RANGING FROM THE LOWER 90S
(MID-ATLANTIC) TO THE MID 80S (NORTHERN NEW ENGLAND) WHICH WOULD BE BELOW
HAZARDOUS THRESHOLDS.
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. UNLIKE PREVIOUS DAYS, THE LATEST MODEL
GUIDANCE DEPICTS A FAVORABLE MID-LEVEL PATTERN PERSISTING, RESULTING IN THE
HEAVY PRECIPITATION HAZARD BEING VALID THROUGH THE ENTIRETY OF WEEK-2. 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 6) 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 EASTWARD OVER AFRICA 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
OF THE TROPICAL ATLANTIC THROUGH LATE AUGUST. THE LATEST MODEL RUNS ARE KEYING
ON ANOTHER TROPICAL WAVE ENTERING THE EASTERN ATLANTIC BY EARLY NEXT WEEK AND
MANY GEFS AND ECENS FAVOR THIS BECOMING A TC DURING WEEK-2 ACROSS THE MAIN
DEVELOPMENT REGION.
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 ON AUGUST 14TH WAS MAINTAINED FOR FORECAST
CONTINUITY. GIVEN THE COLDER-THAN-NORMAL TEMPERATURES, PERIODS OF SNOW ARE
EXPECTED TO AFFECT THE BROOKS RANGE.
FORECASTER: BRAD PUGH
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