403
FXUS21 KWNC 091808
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 09 2024
SYNOPSIS: EXCESSIVE HEAT IS FORECAST TO CONTINUE INTO THE WEEK-2 PERIOD ACROSS
PORTIONS OF THE SOUTHERN PLAINS AND LOWER-MISSISSIPPI VALLEY BENEATH MID-LEVEL
HIGH PRESSURE CENTERED ACROSS THE CENTRAL CONTIGUOUS U.S. (CONUS). THERE ARE
SOME SIGNALS THAT PRECIPITATION IN THE SOUTHWEST MAY PICK BACK UP WITH A
RE-STRENGTHENING OF THE MONSOON CIRCULATION. IN THE MID-ATLANTIC, A STATIONARY
FRONT AND SURFACE LOW-PRESSURE MAY BRING INCREASED CHANCES FOR HEAVY
PRECIPITATION. THIS MAY INDUCE ADDITIONAL FLOODING FOLLOWING HEAVY
PRECIPITATION OVER THE PAST SEVERAL DAYS. MEANWHILE, A TROPICAL SYSTEM MAY
INTERACT WITH PORTIONS OF FLORIDA EARLY IN WEEK-2. 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, NORTHERN TEXAS, AND THE LOWER MISSISSIPPI VALLEY.
HAZARDS
MODERATE RISK OF EXCESSIVE HEAT FOR PORTIONS OF THE SOUTHEAST, LOWER
MISSISSIPPI VALLEY, AND SOUTHERN PLAINS, SAT-MON, AUG 17-19.
SLIGHT RISK OF EXCESSIVE HEAT FOR PORTIONS OF THE SOUTHERN PLAINS, LOWER
MISSISSIPPI VALLEY AND SOUTHEAST, SAT-FRI, AUG 17-23.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE SOUTHWEST, SAT-MON, AUG
17-19.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE MID-ATLANTIC, SAT-MON,
AUG 17-19.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PORTIONS OF THE FLORIDA PENINSULA,
SAT-TUE, AUG 17-20.
SLIGHT RISK FOR EPISODES OF HIGH WINDS FOR PORTIONS OF THE FLORIDA PENINSULA,
SAT-TUE, AUG 17-20.
RAPID ONSET DROUGHT RISK FOR PORTIONS OF THE SOUTHERN PLAINS AND LOWER
MISSISSIPPI VALLEY.
FLOODING POSSIBLE RISK FOR PORTIONS OF THE MID-ATLANTIC AND SOUTHEAST.
DETAILED SUMMARY
FOR MONDAY AUGUST 12 - FRIDAY AUGUST 16:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY AUGUST 17 - FRIDAY AUGUST 23: MODELS GENERALLY AGREE ON THE
EVOLUTION OF THE MID-LEVEL HEIGHT 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 ALONG 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 ARE EXPECTED TO 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 GREAT PLAINS, WITH THE HOTTEST WEATHER EXPECTED ACROSS THE SOUTHERN HALF OF
THE GREAT PLAINS AND LOWER MISSISSIPPI VALLEY. 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 THE GEFS AND ECENS SHOW AN AREA OF
GREATER THAN 40% CHANCES OF MAXIMUM TEMPERATURES EXCEEDING THE 85TH PERCENTILE
IN THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY. THE PETS HAVE REGAINED
SOME STRENGTH RELATIVE TO YESTERDAY BUT HAVE MAINTAINED A SIMILAR AREA OF
HIGHEST RISK FOR EXCESSIVE HEAT. THE SKILL WEIGHTED BIAS-CORRECTED APPARENT
TEMPERATURE TOOL FORECASTS HEAT INDICES TO EXCEED 110 DEG F ACROSS MUCH OF THE
REGION. SOME TOOLS INDICATE THERE MAY BE A SLIGHT REDUCTION IN TEMPERATURES ON
DAYS 9 AND 10 BUT TOOLS GENERALLY CONTINUE TO SUPPORT A MODERATE RISK OF
EXCESSIVE HEAT REMAINING THROUGH DAY 10. THEREFORE, A MODERATE RISK OF
EXCESSIVE HEAT REMAINS POSTED FOR AUG 17-19 ACROSS PORTIONS OF THE LOWER
MISSISSIPPI VALLEY AND SOUTHERN PLAINS. A BROADER SLIGHT RISK IS MAINTAINED
THROUGH THE WEEK-2 PERIOD WITH CONTINUED CHANCES (20-40%) FROM THE PETS FOR
TEMPERATURES EXCEEDING THE 85TH PERCENTILE ACROSS MUCH OF THE SOUTH-CENTRAL
CONUS.
BELOW-NORMAL RAINFALL ANTICIPATED OVER MUCH OF THE SOUTHERN PLAINS AND LOWER
MISSISSIPPI VALLEY DURING WEEK-2, COMBINED WITH INCREASED LIKELIHOOD OF
EXCESSIVE HEAT AND BELOW-NORMAL 30-DAY ACCUMULATED PRECIPITATION, RESULTS IN AN
ELEVATED RISK OF RAPID ONSET DROUGHT. THERE REMAINS TWO AREAS OF GREATEST
CONCERN ACROSS THE SOUTHERN PLAINS AND LOWER MISSISSIPPI VALLEY SUPPORTED BY
DECLINING SOIL MOISTURE VALUES AND DRY CONDITIONS FAVORED OVER THE NEXT TWO
WEEKS. MUCH OF THIS REGION IS ALREADY IDENTIFIED AS ABNORMALLY DRY (D0) ON THE
U.S. DROUGHT MONITOR.
IN THE SOUTHWEST, THERE ARE SOME MORE ENHANCED SIGNALS FOR HEAVY PRECIPITATION
IN THE ECENS PET. THE SIGNALS HAVE BEEN CONSISTENT AND GROWN STRONGER OVER THE
PAST SEVERAL DAYS, HOWEVER, THE GEFS IS YET TO SHOW THIS SIGNAL. THE RAW
PRECIPITATION TOTALS FROM THE ECENS SHOW CHANCES FOR 3 DAY PRECIPITATION
AMOUNTS TO EXCEED HALF AN INCH IN PORTIONS OF THE SOUTHWEST. THE INCREASE IN
PRECIPITATION WOULD ALSO BE CONSISTENT WITH THE RETROGRADING MID-LEVEL RIDGE
FORECAST ACROSS THE CENTRAL CONUS. AS SUCH, A SLIGHT RISK OF HEAVY
PRECIPITATION IS POSTED TODAY FOR AUG 17-19 FOR PORTIONS OF THE FOUR CORNERS
REGION.
BY AUGUST 17, A WARM FRONT IS FORECAST TO BE LIFTING NORTH THROUGH THE
MID-ATLANTIC WITH AN ASSOCIATED SURFACE LOW-PRESSURE MOVING EAST ALONG THIS
BOUNDARY. THIS SYSTEM MAY BRING INCREASED CHANCES FOR HEAVY PRECIPITATION TO
PORTIONS OF THE MID-ATLANTIC. THIS IS SUPPORTED BY THE ECENS PET AND THE RAW
DYNAMICAL TOOLS. THE GEFS IS WEAKER WITH THE SYSTEM BUT THERE IS INCREASED
SUPPORT IN THE GEFS PET TODAY RELATIVE TO YESTERDAY. THEREFORE, A SLIGHT RISK
OF HEAVY PRECIPITATION IS POSTED FOR AUG 17-19. FOLLOWING THE HEAVY
PRECIPITATION ASSOCIATED WITH POST-TROPICAL DEPRESSION DEBBY EARLY IN WEEK-1.
RIVERS MAY REMAIN SOMEWHAT ELEVATED AND ADDITIONAL PRECIPITATION COULD BRING
INCREASED CHANCES FOR FLOODING. THEREFORE, A FLOODING POSSIBLE RISK COINCIDES
WITH THE SLIGHT RISK HAZARD. THE FLOODING POSSIBLE HAZARD THEN EXTENDS FURTHER
SOUTH OF THE SLIGHT RISK OF HEAVY PRECIPITATION INTO SOUTH CAROLINA AND GEORGIA
CONSISTENT WITH THE FLOOD HAZARD OUTLOOK FROM THE NATIONAL WATER CENTER AS A
RESULT OF RESIDUAL FLOODING FROM HEAVY PRECIPITATION DUE TO POST-TROPICAL
DEPRESSION DEBBY.
THE NATIONAL HURRICANE CENTER IS TRACKING A TROPICAL WAVE OVER THE ATLANTIC. AS
OF 2PM THIS SYSTEM HAS A 60% CHANCE OF FORMATION INTO A TROPICAL CYCLONE OVER
THE NEXT 7 DAYS AS IT TRACKS WESTWARD TOWARDS THE ANTILLES. BY WEEK-2, ENSEMBLE
GUIDANCE IS SUGGESTING TWO POSSIBLE OUTCOMES, THE FIRST IS THE SYSTEM WOULD
RECURVE INTO THE ATLANTIC PRIOR TO REACHING THE U.S EAST COAST. HOWEVER, THERE
ARE SOME SIGNALS FROM THE ENSEMBLE GUIDANCE THAT THIS SYSTEM MAY APPROACH THE
FLORIDA PENINSULA. THERE REMAINS A HIGH DEGREE OF UNCERTAINTY REGARDING THE
EVOLUTION OF THIS TROPICAL SYSTEM. NEVERTHELESS, A SLIGHT RISK OF HEAVY
PRECIPITATION AND HIGH WINDS IS POSTED FOR PORTIONS OF SOUTHEASTERN FLORIDA FOR
AUG 17-20. FOLLOW THE NATIONAL HURRICANE CENTER FOR MORE DETAILS AS THIS SYSTEM
MOVES WESTWARD TOWARDS THE WESTERN ATLANTIC.
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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