906
FXUS21 KWNC 311804
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 31 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
POTENTIALLY EXCESSIVE HEAT OVER MUCH OF THE WESTERN AND CENTRAL U.S. EARLY
WEEK-2. HOWEVER, AN AMPLIFYING MID-LEVEL RIDGE IN NORTHERN CANADA FAVORS A PUSH
OF COOLER AIR INTO THE CENTRAL AND EASTERN CONUS FROM THE NORTH, BEFORE THE
MIDDLE OF WEEK-2, QUICKLY ENDING ANY HEAT THREAT. FARTHER WEST, WARMER THAN
NORMAL WEATHER AND POTENTIALLY EXCESSIVE HEAT PERSISTS FOR A FEW MORE DAYS
BEFORE THE BROAD MID-LEVEL HIGH PRESSURE WEAKENS. POSSIBLE TROPICAL CYCLONE
DEVELOPMENT IN THE WESTERN ATLANTIC COULD AFFECT PARTS OF THE CENTRAL GULF
COAST AND EASTERN SEABOARD, BUT UNCERTAINTY REMAINS HIGH.
HAZARDS
SLIGHT RISK OF EXCESSIVE HEAT FROM PORTIONS OF THE CENTRAL GREAT PLAINS THROUGH
THE
TENNESSEE VALLEY, LOWER OHIO VALLEY, AND THE MIDDLE AND LOWER MISSISSIPPI
VALLEY, THU, AUG
8.
SLIGHT RISK OF EXCESSIVE HEAT FOR MUCH OF THE SOUTHERN PLAINS AND WESTERN
CONUS, THU-SAT,
AUG 8-10.
SLIGHT RISK FOR HEAVY PRECIPITATION ACROSS THE CENTRAL GULF COAST, FLORIDA, AND
MUCH OF THE
EASTERN SEABOARD, THU-SAT, AUG 8-10.
SLIGHT RISK FOR HIGH WINDS ALONG PART OF THE IMMEDIATE CENTRAL GULF COAST AND
EAST COAST,
THU-SAT, AUG 8-10.
RAPID ONSET DROUGHT RISK FOR MUCH OF THE GREAT PLAINS INTO WESTERN MISSOURI.
DETAILED SUMMARY
FOR SATURDAY AUGUST 03 - WEDNESDAY AUGUST 07:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY AUGUST 08 - WEDNESDAY AUGUST 14: 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. THE LATEST GEFS, ECENS, AND CANADIAN ENSEMBLES ARE ALL WEAKER
WITH A DEVELOPING MID-LEVEL TROUGH ACROSS EASTERN CANADA THAN YESTERDAY, BUT
BUILD A MUCH STRONGER MID-LEVEL RIDGE INTO THE NORTHERN REACHES OF CANADA. THIS
WOULD FAVOR A PUSH OF COOLER AIR FROM THE NORTH INTO THE CENTRAL AND EASTERN
CONUS, WHICH SHOULD BRING A QUICK END TO ANY EXCESSIVE HEAT THREAT AFTER THE
FIRST DAY OF WEEK-2 EAST OF THE PLAINS. THE ECENS AND CANADIAN ENSEMBLES AND
THEIR DERIVED PROBABILISTIC EXTREMES TOOLS (PETS) ARE CONSIDERABLY QUICKER AND
STRONGER WITH THIS PUSH OF COOLER AIR, BUT FOR NOW THE SLOWER AND WARMER GEFS
SOLUTION IS FAVORED, WHICH IS MORE CONSISTENT WITH YESTERDAY’S GUIDANCE. THE
GEFS PET MAINTAINS A GREATER THAN 30 PERCENT CHANCE FOR MAXIMUM TEMPERATURES IN
THE UPPER 15TH PERCENTILE OF THE CLIMATOLOGICAL ENVELOPE IN THE AREAS WITH A
SLIGHT RISK OF EXCESSIVE HEAT ON DAY 8 (THU AUG 8). THE SAME TOOL PERSISTS IN
SHOWING AN ELEVATED LIKELIHOOD FOR TEMPERATURES REACHING ABOVE 100 DEG. F IN
THE SOUTHERN HALF OF THE PLAINS, WITH SUBSTANTIAL ODDS FOR TEMPERATURES TO
REACH 95 DEG. F OR HIGHER FROM THE LOWER OHIO VALLEY TO THE SOUTH AND WEST,
WHERE RELATIVELY HIGH HUMIDITY IS EXPECTED TO BOOST HEAT INDEXES INTO THE
TRIPLE DIGITS. IN ADDITION, THE NATIONAL BLEND OF MODELS INDICATES ELEVATED
CHANCES FOR DAILY-RECORD-HIGH MINIMUM TEMPERATURES IN THIS REGION. FOLLOWING
DAY 8 (AUG 8), IT IS UNCERTAIN HOW FAR SOUTH THE COOLER AIR ADVANCES, SO SOME
LINGERING RISK OF EXCESSIVE HEAT WILL PERSIST IN THE SOUTHERN PLAINS FOR A
COUPLE OF ADDITIONAL DAYS, AGAIN MOST CONSISTENT WITH THE GEFS RATHER THAN THE
COOLER ECENS AND CANADIAN ENSEMBLE SOLUTIONS.
THERE ARE SOME INDICATIONS THAT HEAVY RAINFALL MAY BE TRIGGERED AT TIMES ALONG
THE LEADING EDGE OF THE COOLER AIR HEADED SOUTHWARD INTO THE CENTRAL CONUS,
PARTICULARLY ALONG THE FRONT RANGE OF THE CENTRAL ROCKIES WHERE UPSLOPING WINDS
COULD ENHANCE RAINFALL TOTALS. THE COOLER AND WETTER WEATHER WOULD BENEFIT THE
CONTAINMENT OF SEVERAL LARGE WILDFIRES THAT HAVE PLAGUED THE REGION RECENTLY,
BUT COULD ALSO TRIGGER LOCALIZED FLASH FLOODING IF IT FALLS ON AREAS THAT HAVE
BEEN DENUDED BY THE WILDFIRES. HOWEVER, THE QUANTITY AND LOCATION OF ANY
PRECIPITATION ASSOCIATED WITH THIS FRONTAL SYSTEM ARE HIGHLY UNCERTAIN, SO NO
SPECIFIC HAZARD IS POSTED AT THIS TIME.
FARTHER WEST, THE FLATTENING MID-LEVEL RIDGE SHOULD BRING ABOUT A SLOW
REDUCTION IN TEMPERATURES THAT WOULD HAVE BEGUN LATE WEEK-1, ENDING ANY
EXCESSIVE HEAT THREAT BY MID-WEEK. THE PETS FROM ALL THREE ENSEMBLES MAINTAIN A
20 TO 40 PERCENT CHANCE FOR MAXIMUM TEMPERATURES REACHING THE TOP 15TH
PERCENTILE OF THE CLIMATOLOGICAL ENVELOPE OVER MUCH OF THE CONUS FROM THE
CENTRAL ROCKIES SOUTHWARD AND WESTWARD AS WEEK-2 BEGINS, BUT THIS COVERAGE
SLOWLY DECREASES EACH DAY, AND BY MID-WEEK, ONLY THE GEFS PET SHOWS ANY
SIGNIFICANT COVERAGE REMAINING.
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. MODELS REMAIN VERY INCONSISTENT IN THEIR TREATMENT OF THIS
FEATURE, AS WAS THE CASE YESTERDAY. 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. MEANWHILE, THE OPERATIONAL GFS AND A FEW MEMBERS
OF THE GEFS AND ECENS TRACK THIS SYSTEM INTO THE GULF OF MEXICO, EITHER ACROSS
FLORIDA OR NORTHWARD FROM THE CARIBBEAN SEA. GIVEN THE CURRENT ARRAY OF
POSSIBILITIES, THERE IS A LARGE AREA FROM THE CENTRAL GULF COAST THROUGH
FLORIDA AND MUCH OF THE EASTERN SEABOARD THAT MIGHT BE AFFECTED BY A TROPICAL
SYSTEM IF ONE DEVELOPS. THUS, SLIGHT RISKS OF HEAVY PRECIPITATION AND HIGH
WINDS ARE DESIGNATED FOR THESE REGIONS. THE FORWARD SPEED OF THE SYSTEM IS
ANOTHER ASPECT THAT REMAINS HIGHLY UNCERTAIN AT THIS TIME, BUT SOME OF THE
GUIDANCE MOVES THE SYSTEM MORE SLOWLY OUT OF THE ATLANTIC OCEAN OR GULF OF
MEXICO THAN INDICATED YESTERDAY, SO THE SLIGHT RISKS OF HEAVY RAIN AND HIGH
WINDS ARE EXTENDED THROUGH AUG 8-10 (DAYS 8-10 OF WEEK-2).
ABOVE-AVERAGE TEMPERATURES IN THE WEST FAVOR STRENGTHENING THERMAL GRADIENTS
AND ELEVATED WIND SPEEDS OVER SOME AREAS.TOOLS DO NOT DEPICT A WIDESPREAD
SIGNAL FOR HIGH WINDS, PRECLUDING ANY HAZARD FROM BEING POSTED, BUT LOCALIZED
HIGH WINDS COMBINED WITH THE INITIALLY HOT AND DRY CONDITIONS WEEK-2 ARE LIKELY
TO KEEP AN ENHANCED RISK OF WILDFIRES ACROSS MUCH OF THE WEST, AND HINDERING
EFFORTS TO CONTAIN ANY ONGOING INCIDENTS. THESE THREATS SHOULD SLOWLY DECLINE
ALONG WITH TEMPERATURES AS WEEK-2 PROGRESSES.
BELOW-NORMAL PRECIPITATION AND ABOVE-NORMAL TEMPERATURES FOR THE NEXT 7 TO 10
DAYS 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 NORTHERN AND CENTRAL PARTS OF THIS REGION
EARLY WEEK-2. 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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