538
FXUS21 KWNC 061845
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 06 2024
SYNOPSIS: FLOODING FROM TROPICAL STORM DEBBY MAY LINGER INTO THE EARLY PORTIONS
OF WEEK-2 ALONG THE EASTERN SEABOARD. EXCESSIVE HEAT MAY IMPACT PORTIONS OF THE
SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY BENEATH MID-LEVEL HIGH PRESSURE
CENTERED ACROSS THE SOUTH-CENTRAL CONTIGUOUS U.S. (CONUS). ABOVE-NORMAL
TEMPERATURES AND BELOW-NORMAL PRECIPITATION ALONG WITH LIMITED ANTECEDENT
RAINFALL LEADS TO A RISK OF RAPID ONSET DROUGHT FOR PORTIONS OF THE TEXAS
PANHANDLE, SOUTHERN OKLAHOMA, AND NORTHERN TEXAS.
HAZARDS
SLIGHT RISK OF EXCESSIVE HEAT FOR PORTIONS OF THE SOUTHERN PLAINS, LOWER
MISSISSIPPI VALLEY AND SOUTHEAST, WED-SUN, AUG 14-18.
RAPID ONSET DROUGHT RISK FOR PORTIONS OF THE SOUTHERN PLAINS.
FLOODING POSSIBLE RISK FOR MUCH OF THE EASTERN SEABOARD
DETAILED SUMMARY
FOR FRIDAY AUGUST 09 - TUESDAY AUGUST 13:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY AUGUST 14 - TUESDAY AUGUST 20: MODELS GENERALLY AGREE ON THE
EVOLUTION OF THE MID-LEVEL PATTERN ACROSS NORTH AMERICA DURING WEEK-2. THE
PERIOD STARTS WITH A RIDGE AXIS EXTENDING SOUTHWARD FROM NORTH-CENTRAL CANADA
INTO THE SOUTHERN PLAINS. MID-LEVEL TROUGHS ARE EXPECTED ACROSS BOTH THE EAST
AND WEST COASTS. AS THE WEEK PROGRESSES, THE TROUGHS NEAR THE COASTS ARE
FORECAST TO SLOWLY WEAKEN WHILE THE MID-CONTINENT RIDGE MAINTAINS ITS STRENGTH
AND RETROGRADES SLIGHTLY. BY THE END OF WEEK-2, WEAK REMNANTS OF THE MID-LEVEL
TROUGHS SHOULD BE OVER OR NEAR THE EASTERN AND WESTERN PORTIONS OF NORTH
AMERICA WITH A MID-LEVEL RIDGE EXTENDING FROM THE EASTERN FOUR CORNERS REGION
NORTHWARD ROUGHLY ALONG THE FRONT RANGE OF THE ROCKIES NORTHWARD INTO
NORTH-CENTRAL CANADA. IN ALASKA, MID-LEVEL TROUGHING IS GENERALLY FAVORED AMONG
THE TOOLS THROUGHOUT MUCH OF THE PERIOD.
ABOVE-NORMAL TEMPERATURES ARE FAVORED ALONG THE MID-LEVEL RIDGE AXIS THROUGH
THE PLAINS, WITH THE HOTTEST WEATHER EXPECTED ACROSS THE SOUTHERN HALF OF THE
GREAT PLAINS AND LOWER MISSISSIPPI VALLEY, WHERE THERE IS A SLIGHT RISK OF
EXCESSIVE HEAT FOR AUG 14-18. THE CENTER OF THE MID-LEVEL RIDGE IS EXPECTED TO
MOVE VERY LITTLE UNTIL THE END OF THE PERIOD. THE PROBABILISTIC EXTREMES TOOLS
(PETS) FOR ALL THREE ENSEMBLES SHOW ENHANCED CHANCES FOR MAXIMUM TEMPERATURES
TO EXCEED THE 85TH PERCENTILE IN THE SOUTHERN PLAINS AND SOME ADJACENT AREAS AT
THE START OF WEEK-2, AND THE PETS DERIVED FROM THE ECENS AND GEFS KEEP THE
ELEVATED RISK IN PLACE FOR MUCH OF THE WEEK. FROM THE SOUTHEASTERN PLAINS INTO
THE LOWER MISSISSIPPI VALLEY, RELATIVELY HIGH DEW POINTS ARE EXPECTED TO
INCREASE HEAT INDICES POTENTIALLY INTO THE EXCESSIVE HEAT RANGE. FARTHER WEST,
THE ACTUAL TEMPERATURES ARE EXPECTED TO APPROACH OR EXCEED THE EXCESSIVE HEAT
THRESHOLD.
IN FLORIDA, THERE ARE SOME CONCERNS THAT APPARENT TEMPERATURES MAY REACH
HAZARDOUS THRESHOLDS EARLY IN THE PERIOD. HOWEVER, THERE REMAINS QUITE A BIT OF
UNCERTAINTY WITH SOME OF THE PETS INDICATING 20 TO 30% CHANCES OF TEMPERATURES
EXCEEDING THE 85TH PERCENTILE, WHILE RAW ENSEMBLE TEMPERATURES FROM THE GEFS
AND ECENS KEEP TEMPERATURES BELOW 95 DEG F WHICH WOULD BE UNLIKELY TO CAUSE
HAZARDOUS HEAT. FURTHER, THE GLOBAL TROPICAL HAZARDS FORECAST IS INDICATING A
MODERATE CHANCE OF TROPICAL CYCLONE DEVELOPMENT OFF THE SOUTHEASTERN CONUS
INCREASING UNCERTAINTY IN THE REGION.
BELOW-NORMAL RAINFALL IS ANTICIPATED OVER MUCH OF THE SOUTHERN PLAINS DURING
WEEK-2, AND IN AREAS WITH A COINCIDING RISK OF EXCESSIVE HEAT AND SIGNIFICANTLY
BELOW-NORMAL 30-DAY RAINFALL, RESULTING IN AN ELEVATED RISK OF RAPID ONSET
DROUGHT. MORE SPECIFICALLY, THIS COVERS AN AREA FROM THE RED RIVER (OF THE
SOUTH) VALLEY WESTWARD, INCLUDING MUCH OF OKLAHOMA AND NORTHERN TEXAS. MUCH OF
THIS REGION IS ALREADY IDENTIFIED AS ABNORMALLY DRY (D0) ON THE U.S. DROUGHT
MONITOR.
DURING WEEK-1, EXCESSIVE RAINFALL IS EXPECTED IN ASSOCIATION WITH SLOW-MOVING
TROPICAL STORM DEBBY. CURRENTLY, A LARGE AREA OF FLOODING IS POSSIBLE IN THE
SHORT-TERM FROM CENTRAL FLORIDA NORTHWARD INTO NEW ENGLAND. FOR THE WEEK-2
PERIOD, FLOODING MAY CONTINUE IN THE AREAS EXPECTED TO BE MOST SEVERELY
AFFECTED BY DEBBY AND ASSOCIATED EXCESSIVE RAINFALL DURING WEEK-1, ALONG WITH
SOME AREAS OF VERY WET ANTECEDENT CONDITIONS IN NEW ENGLAND. WATER MODELS FROM
THE NATIONAL WATER CENTER (NWC) HAVE INCREASED CONFIDENCE FOR HIGH STREAM AND
RIVER FLOWS ACROSS THE MID-ATLANTIC AND NEW ENGLAND DURING DAYS 8 TO 10. AS A
RESULT, A LARGE AREA OF POSSIBLE WEEK-2 FLOODING EXTENDS FROM NORTHEASTERN
FLORIDA NORTHWARD ALONG MOST OF THE COASTAL PLAIN AND PIEDMONT OF THE ATLANTIC
SEABOARD, IN ADDITION TO MUCH OF NEW ENGLAND. FURTHER EXPANSION OF THE REGION
WITH POTENTIAL WEEK-2 FLOODING MAY BE NECESSARY AS THE EVOLUTION OF TROPICAL
STORM DEBBY BECOMES MORE CERTAIN LATER THIS WEEK.
WITH A MID-LEVEL TROUGH TO ITS WEST AND A LARGE 500-HPA POSITIVE ANOMALY CENTER
TO THE EAST, UNSETTLED CONDITIONS ARE EXPECTED ACROSS MOST OF ALASKA DURING
WEEK-2, WITH UNUSUALLY HEAVY PRECIPITATION MOST LIKELY IN WESTERN PARTS OF THE
MAINLAND. CURRENTLY, PRECIPITATION AND WIND ARE EXPECTED TO REMAIN BELOW
HAZARDS THRESHOLDS, BUT THE REGION WILL NEED TO BE MONITORED FOR ANY INCREASE
IN PRECIPITATION SHOWN BY THE MODELS.
FORECASTER: RYAN BOLT
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