341
FXUS21 KWNC 301929
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 30 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 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 COULD AFFECT PART
OF THE EASTERN SEABOARD, BUT THIS REMAINS UNCERTAIN.
HAZARDS
MODERATE RISK FOR EXCESSIVE HEAT FOR THE CALIFORNIA VALLEYS, MOJAVE DESERT, AND
ADJACENT NEVADA, WED-THU, AUG 7-8.
MODERATE RISK FOR EXCESSIVE HEAT FOR MUCH OF THE NORTHERN INTERMOUNTAIN WEST,
WED-THU, AUG 7-8.
MODERATE RISK FOR EXCESSIVE HEAT FOR PARTS OF THE CENTRAL AND SOUTHERN PLAINS,
AND THE MIDDLE AND LOWER MISSISSIPPI VALLEY, AND MUCH OF THE OHIO AND TENNESSEE
VALLEYS, WED, AUG 7.
SLIGHT RISK OF EXCESSIVE HEAT FOR MUCH OF THE WESTERN CONUS, CENTRAL AND
SOUTHERN PLAINS, AND THE MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS, WED-FRI, AUG
7-9.
SLIGHT RISK FOR HEAVY PRECIPITATION ACROSS THE FLORIDA PENINSULA AND MUCH OF
THE EASTERN SEABOARD, WED-THU, AUG 7-8.
SLIGHT RISK FOR HIGH WINDS ALONG PART OF THE IMMEDIATE EAST COAST, WED-THU, AUG
7-8.
RAPID ONSET DROUGHT RISK FOR MUCH OF THE GREAT PLAINS INTO WESTERN MISSOURI.
DETAILED SUMMARY
FOR FRIDAY AUGUST 02 - TUESDAY AUGUST 06:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY AUGUST 07 - TUESDAY AUGUST 13: 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 LATER IN THE PERIOD. THE LATEST GEFS, ECENS, AND CANADIAN ENSEMBLES
FAVOR AMPLIFYING MID-LEVEL 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 AND ANOMALOUS WARMTH OVER
MUCH OF THE CONUS. MOST OF THE GUIDANCE FAVORS ABOVE NORMAL TEMPERATURES AND AN
EXCESSIVE HEAT RISK DURING THE FIRST HALF OF WEEK-2, BUT TODAY’S INDICATORS ARE
NOT AS ROBUST AS YESTERDAY. THE PROBABILISTIC EXTREMES TOOL (PET) FOR THE GEFS
DEPICT A 40-60 PERCENT PROBABILITY FOR MAXIMUM TEMPERATURES TO EXCEED THE 85TH
CLIMATOLOGICAL PERCENTILE EARLY WEEK-2 FROM THE CENTRAL PLAINS EASTWARD TO THE
WESTERN FOOTHILLS OF THE APPALACHIANS, BUT THE PETS FROM THE ECENS AND CANADIAN
ENSEMBLE ARE NOT AS BULLISH. FARTHER WEST, THE PETS FROM THE GEFS AND ECENS
HAVE SCATTERED AREAS WITH ABOUT A 40 PERCENT RISK OF EXCESSIVE HEAT FOR THE
FIRST COUPLE OF DAYS OF THE PERIOD. HOWEVER, SIGNALS FOR EXCESSIVE HEAT ARE
REDUCED RELATIVE TO YESTERDAY ACROSS MUCH OF THE GREAT BASIN AND SOME ADJACENT
AREAS, IN THESE AREAS YESTERDAY’S MODERATE HEAT RISK HAS BEEN REMOVED.
UNCALIBRATED GUIDANCE DEPICTS A SUBSTANTIAL RISK FOR 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
HIGH HUMIDITY LIKELY LEADING TO HIGHER HEAT INDICES. A MODERATE RISK FOR
EXCESSIVE HEAT IS HIGHLIGHTED OVER THESE REGIONS FOR AUG 7 BEFORE CONDITIONS
GRADUALLY EASE. TRIPLE DIGIT HEAT IS ALSO POSSIBLE ACROSS LOW ELEVATION
PORTIONS OF THE CALIFORNIA VALLEYS AND INTERMOUNTAIN WEST, WITH SOUTHERN PARTS
OF THIS AREA POSSIBLY REACHING 110 DEG F ACCORDING TO UNCALIBRATED GUIDANCE
FROM THE GEFS AND ECENS. THIS SUPPORTS CONTINUING THE MODERATE RISK OVER THESE
AREAS FOR AUG 7-8. A SLIGHT RISK FOR EXCESSIVE HEAT COVERS A LARGE PART OF THE
CONUS FROM THE FAR WEST INTO THE CENTRAL AND SOUTHERN PLAINS, THE SOUTHERN
GREAT LAKES, AND THE MISSISSIPPI, OHIO, AND TENNESSEE VALLEYS FOR THE FIRST
HALF OF WEEK-2 (AUG 7-9). THE PETS FROM THE GEFS, ECENS, AND CANADIAN ENSEMBLE
BECOME LESS CONSISTENT WITH EACH OTHER AND REDUCE PROBABILITIES FOR MAXIMUM
TEMPERATURES REACHING THE 85TH PERCENTILE TO 20 PERCENT OR LOWER ACROSS MOST OF
THE CONUS LATER WEEK-2, ALTHOUGH THE GEFS MAINTAINS LIMITED COVERAGE THROUGHOUT
ALL OF WEEK-2 OVER A FEW AREAS. THE EVOLVING SYNOPTIC PATTERN FAVORS MODERATING
TEMPERATURES AND DECREASING HUMIDITY, ESPECIALLY ACROSS THE NORTHERN TIER, AS
WEEK-2 PROGRESSES.
THE NATIONAL HURRICANE CENTER IS MONITORING A DISTURBANCE ACROSS THE WESTERN
TROPICAL ATLANTIC WITH A 60 PERCENT CHANCE OF TROPICAL CYCLONE DEVELOPMENT IN
THE NEXT 7-DAYS. MANY ENSEMBLE MEMBERS OF THE ECENS AND A FEW FROM THE GEFS
DEPICT A RECURVING TRACK NEAR OR OFF THE U.S. EAST COAST LATE IN WEEK-1 INTO
EARLY WEEK-2, BUT THE POTENTIAL FOR A TRACK INTO THE GULF OF MEXICO IS SOMEWHAT
INCREASED COMPARED TO YESTERDAY. GIVEN THE CURRENT PROJECTIONS, 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 7-8, WITH ANY IMPACTS DEPENDENT ON HOW CLOSE THE SYSTEM GETS TO THE
COAST. THE SLIGHT RISK AREAS HAVE BEEN EXTENDED SOMEWHAT FARTHER SOUTHWEST THAN
YESTERDAY IN DEFERENCE TO NOMINALLY INCREASED ODDS FOR A TRACK FARTHER SOUTH
INTO THE GULF. THIS SYSTEM MAY CONTRIBUTE TO ENHANCING THE NORTHERLY SURFACE
FLOW PATTERN AND DRY AIR ADVECTION INTO THE EASTERN CONUS LATER WEEK-2, FURTHER
HELPING TO MODERATE ANY 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 HINDER EFFORTS TO CONTAIN ANY ONGOING INCIDENTS. THE
COMBINATION OF ABOVE-NORMAL TEMPERATURES AND BELOW-NORMAL PRECIPITATION FOR THE
NEXT 7 TO 10 DAYS ALSO SUPPORTS THE CONTINUATION OF A RAPID ONSET DROUGHT (ROD)
RISK FROM MOST OF THE GREAT PLAINS INTO WESTERN MISSOURI, ALTHOUGH GUIDANCE
SHOWS TEMPERATURES COOLING OFF SUBSTANTIALLY ACROSS THE NORTH-CENTRAL CONUS
MORE QUICKLY THAN YESTERDAY. STILL, DRY SOILS, STRESSED VEGETATION, AND REDUCED
WATER AVAILABILITY DUE TO LOW PONDS AND STREAM FLOWS 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 A WARM START TO WEEK-2 IN THE EASTERN HALF OF THE STATE,
AND AN ACTIVE STORM TRACK POTENTIALLY AFFECTING PORTIONS OF SOUTHERN AND
WESTERN ALASKA WITH INCREASING CHANCES FOR PRECIPITATION. THERE MAY BE SOME
ENHANCED RISK OF WILDFIRES IN PARTS OF EASTERN ALASKA, PARTICULARLY EARLY IN
THE PERIOD WHEN IT’S EXPECTED TO BE WARM AND DRIER THAN NORMAL. ALTHOUGH THERE
ARE SOME ELEVATED SIGNALS IN THE PETS FOR 3-DAY PRECIPITATION TOTALS REACHING
THE 85TH CLIMATOLOGICAL PERCENTILE AND 1-INCH OVER SOUTHWESTERN AND/OR
SOUTH-CENTRAL ALASKA, THE TIMING AND LOCATIONS FOR ANY ENHANCED PRECIPITATION
ARE NOT CONSISTENT AND WOULD MARGINALLY APPROACH HAZARDS THRESHOLDS AT BEST, SO
NO HAZARDS ARE POSTED. NEAR JUNEAU, LOCALIZED FLOODING MAY BE A CONCERN
ASSOCIATED WITH THE GLACIAL OUTBURST FLOOD FOR THE MENDENHALL RIVER.
FORECASTER: RICH TINKER
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