253
FXUS21 KWNC 291841
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 29 2024
SYNOPSIS: BROAD MID-LEVEL HIGH PRESSURE IS FORECAST ACROSS THE CONTIGUOUS U.S.
(CONUS) AT THE OUTSET OF THE PERIOD, WITH ANOMALOUSLY WARM TEMPERATURES AND
EXCESSIVE HEAT CONDITIONS PERSISTING OVER MUCH OF THE WESTERN AND CENTRAL U.S.
EARLY IN WEEK-2. HOWEVER, AN AMPLIFYING MID-LEVEL LOW ACROSS EASTERN CANADA
FAVORS A FLATTENING OF THE MID-LEVEL PATTERN ACROSS THE CONUS BY THE MIDDLE OF
WEEK-2 AND A MODERATION IN TEMPERATURES, PARTICULARLY ACROSS THE NORTHERN TIER.
POSSIBLE TROPICAL CYCLONE DEVELOPMENT IN THE WESTERN ATLANTIC WITH A SUBSEQUENT
TRACK OFF THE EASTERN SEABOARD RAISES SOME CONCERNS FOR RELATED IMPACTS ALONG
THE EAST COAST, BUT THIS IS HIGHLY UNCERTAIN.
HAZARDS
MODERATE RISK FOR EXCESSIVE HEAT FOR PARTS OF THE GREAT BASIN, CALIFORNIA, AND
SOUTHWEST, TUE-THU, AUG 6-8.
MODERATE RISK FOR EXCESSIVE HEAT FOR PARTS OF THE CENTRAL AND SOUTHERN PLAINS,
AND THE MIDDLE AND LOWER MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, TUE-WED, AUG
6-7.
SLIGHT RISK OF EXCESSIVE HEAT FOR MUCH OF THE WESTERN CONUS, CENTRAL AND
SOUTHERN PLAINS, MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, AND SOUTHERN GREAT
LAKES, TUE-SAT, AUG 6-10.
SLIGHT RISK FOR HEAVY PRECIPITATION ALONG THE EASTERN SEABOARD, TUE-THU, AUG
6-8.
SLIGHT RISK FOR HIGH WINDS ALONG THE EASTERN SEABOARD, TUE-THU, AUG 6-8.
RAPID ONSET DROUGHT RISK FOR MUCH OF THE GREAT PLAINS, AND INTO WESTERN
MISSOURI.
DETAILED SUMMARY
FOR THURSDAY AUGUST 01 - MONDAY AUGUST 05:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY AUGUST 06 - MONDAY AUGUST 12: A TRANSITIONAL 500-HPA PATTERN IS
PREDICTED ACROSS THE CONUS DURING WEEK-2, WITH BROAD RIDGING FORECAST ACROSS
THE CONUS AT THE OUTSET OF THE PERIOD, FOLLOWED BY A MORE ZONAL MID-LEVEL FLOW
PATTERN BY THE SECOND HALF OF THE PERIOD. THE 0Z GEFS AND ECENS FAVORS
AMPLIFYING TROUGHING ACROSS EASTERN CANADA, FAVORING AN INCREASE IN NORTHERLY
FLOW ACROSS PARTS OF THE NORTHERN TIER AND A GRADUAL REDUCTION OF THE POSITIVE
500-HPA HEIGHT ANOMALIES OVER MUCH OF THE CONUS. EXCESSIVE HEAT REMAINS A
CONCERN EARLY IN WEEK-2, WITH DECENT SIGNALS IN THE GUIDANCE ACROSS THE WEST
AND ALSO OVER PARTS OF THE GREAT PLAINS AND LOWER MIDWEST. THE GEFS AND ECENS
PROBABILISTIC EXTREMES TOOLS (PETS) DEPICT 40-60 PERCENT PROBABILITIES FOR
MAXIMUM TEMPERATURES TO EXCEED THE 85TH PERCENTILE OVER PARTS OF THESE AREAS.
UNCALIBRATED GUIDANCE DEPICTS TEMPERATURES EXCEEDING 100 DEG F ACROSS PORTIONS
OF THE CENTRAL AND SOUTHERN PLAINS, AND 95 DEG F FURTHER EAST ACROSS THE MIDDLE
AND LOWER MISSISSIPPI, TENNESSEE, AND OHIO VALLEYS, WITH HUMIDITY BEING MORE OF
A FACTOR IN THESE AREAS LEADING TO HIGHER HEAT INDICES. A MODERATE RISK FOR
EXCESSIVE HEAT IS HIGHLIGHTED OVER THESE REGIONS FOR AUG 6-7. TRIPLE DIGIT HEAT
IS ALSO POSSIBLE ACROSS LOW ELEVATION PORTIONS OF THE GREAT BASIN, THE
CALIFORNIA CENTRAL VALLEY, AND SOUTHWEST, WITH AREAS FURTHER SOUTH MORE LIKELY
TO HAVE MAXIMUM TEMPERATURES GREATER THAN 105-110 DEG F. THIS SUPPORTS ANOTHER
MODERATE RISK OVER THESE AREAS VALID AUG 6-8. THE SLIGHT RISK FOR EXCESSIVE
HEAT COVERS MUCH OF THE WESTERN CONUS, AND EXTENDS INTO THE CENTRAL AND
SOUTHERN PLAINS, MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, AND SOUTHERN GREAT
LAKES FOR AUG 6-10. THE ECENS PET REDUCES PROBABILITIES FOR MAXIMUM
TEMPERATURES REACHING THE 85TH PERCENTILE BELOW 20 PERCENT ACROSS MOST OF THE
CONUS DURING THE SECOND HALF OF THE PERIOD, ALTHOUGH THE GEFS MAINTAINS SOME
COVERAGE THROUGHOUT ALL OF WEEK-2. THE EVOLVING SYNOPTIC PATTERN FAVORS
MODERATING TEMPERATURES AND DECREASING HUMIDITY, ESPECIALLY ACROSS THE NORTHERN
TIER.
THE NATIONAL HURRICANE CENTER IS MONITORING A DISTURBANCE ACROSS THE WESTERN
TROPICAL ATLANTIC WITH A 50 PERCENT CHANCE OF TROPICAL CYCLONE DEVELOPMENT IN
THE NEXT 7-DAYS. MANY ENSEMBLE MEMBERS OF THE GEFS AND ECENS DEPICT A RECURVING
TRACK NEAR OR OFF THE U.S. EAST COAST LATE IN WEEK-1 INTO EARLY WEEK-2,
ALTHOUGH THERE ARE SOME OUTLIERS THAT ENTER THE GULF OF MEXICO. GIVEN THE
CURRENT PROJECTION OF THE SYSTEM RECURVING WITH MANY MEMBERS REMAINING TOO FAR
OFFSHORE FOR DIRECT IMPACTS, SLIGHT RISKS OF HEAVY PRECIPITATION AND HIGH WINDS
ARE DESIGNATED ONLY FOR THE IMMEDIATE EAST COAST FOR AUG 6-8, WITH ANY IMPACTS
DEPENDENT ON HOW CLOSE THE SYSTEM GETS TO THE COAST. THIS SYSTEM MAY ALSO
CONTRIBUTE TO ENHANCING THE NORTHERLY FLOW PATTERN AND DRY AIR ADVECTION ACROSS
THE EASTERN CONUS IN WEEK-2 FURTHER HELPING TO MODERATE EXCESSIVE HEAT.
ABOVE-AVERAGE TEMPERATURES IN THE WEST FAVOR STRENGTHENING THERMAL GRADIENTS
AND ELEVATED WIND SPEEDS OVER SOME AREAS. WHILE TOOLS DO NOT DEPICT A
WIDESPREAD SIGNAL FOR HIGH WINDS PRECLUDING A RELATED HAZARD, LOCALIZED HIGH
WINDS COMBINED WITH HOT AND DRY CONDITIONS ARE LIKELY TO LEAD TO AN ENHANCED
RISK OF WILDFIRES, AND INHIBIT EFFORTS TO CONTAIN ANY ONGOING INCIDENTS. THE
COMBINATION OF ABOVE-NORMAL TEMPERATURES AND BELOW-NORMAL PRECIPITATION FOR THE
NEXT WEEK TO 10-DAYS ALSO SUPPORTS THE CONTINUATION OF A RAPID ONSET DROUGHT
(ROD) RISK FROM MOST OF THE GREAT PLAINS INTO WESTERN MISSOURI. DRY SOILS,
STRESSED VEGETATION, AND REDUCED WATER AVAILABILITY DUE TO LOW PONDS AND
STREAMS MAY LEAD TO INCREASED IMPACTS TO AGRICULTURE AND LIVESTOCK, WITH SOME
LOCATIONS ALREADY EXPERIENCING IMPACTS.
A MORE AMPLIFIED PATTERN IS FORECAST ACROSS ALASKA DURING WEEK-2, WITH
TROUGHING OVER THE BERING STRAIT AND RIDGING OVER MUCH OF THE MAINLAND AND
SOUTHEAST. THIS FAVORS AN ACTIVE STORM TRACK INTO WESTERN ALASKA WITH
INCREASING CHANCES FOR PRECIPITATION. HAZARDS THRESHOLDS ARE NOT FORECAST TO BE
REACHED, ALTHOUGH THERE ARE SOME ELEVATED SIGNALS IN THE PETS FOR 3-DAY
PRECIPITATION TOTALS REACHING THE 85TH CLIMATOLOGICAL PERCENTILE AND 1-INCH
OVER SOUTHWESTERN ALASKA. NEAR JUNEAU, LOCALIZED FLOODING MAY BE A CONCERN
ASSOCIATED WITH THE GLACIAL OUTBURST FLOOD FOR THE MENDENHALL RIVER.
FORECASTER: THOMAS COLLOW
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