179
FXUS21 KWNC 211836
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 21 2024
SYNOPSIS: MODEL ENSEMBLES DEPICT HIGH PRESSURE BOTH AT THE SURFACE AND
MID-LEVELS ACROSS MUCH OF THE CONTIGUOUS U.S. (CONUS) EARLY IN THE FORECAST
PERIOD, LEADING TO THE POTENTIAL FOR EXCESSIVE HEAT FOR PORTIONS OF THE GREAT
PLAINS AND THE OHIO AND MISSISSIPPI VALLEYS. PROLONGED RAINFALL DEFICITS
COMBINED WITH CONTINUED ABOVE-NORMAL TEMPERATURES RESULTS IN THE POTENTIAL FOR
RAPID ONSET DROUGHT FOR PARTS OF THE SOUTHERN PLAINS AND MISSISSIPPI VALLEY.
HAZARDS
SLIGHT RISK OF EXCESSIVE HEAT FOR PORTIONS OF THE MISSISSIPPI, TENNESSEE, AND
OHIO VALLEYS, GREAT LAKES, AND SOUTHEAST U.S., THU-FRI, AUG 29-30.
RISK FOR RAPID ONSET DROUGHT FOR PORTIONS OF THE SOUTHERN PLAINS, AND LOWER AND
MIDDLE MISSISSIPPI VALLEY.
DETAILED SUMMARY
FOR SATURDAY AUGUST 24 - WEDNESDAY AUGUST 28:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY AUGUST 29 - WEDNESDAY SEPTEMBER 04: TODAY’S MODEL SOLUTIONS FOR
500 HPA HEIGHTS AND ANOMALIES DEPICT BROAD RIDGING OVER THE CONUS AT THE OUTSET
OF WEEK-2 WITH A RIDGE AXIS ROUGHLY OVER THE GREAT PLAINS. THIS RIDGE WEAKENS
GRADUALLY THROUGHOUT THE FORECAST PERIOD AS A WEAK TROUGH BEGINS TO TAKE SHAPE
OVER THE GREAT LAKES REGION. THE EARLY RIDGING LEADS TO THE POTENTIAL FOR
EXCESSIVE HEAT FOR PORTIONS OF THE CENTRAL AND EASTERN CONUS. THE GEFS AND
ECMWF PROBABILISTIC EXTREMES TOOLS (PETS) BOTH INDICATE AT LEAST A 20%
PROBABILITY OF MAXIMUM TEMPERATURES EXCEEDING THE 90TH PERCENTILE AND 90F AS
FAR NORTH AS CHICAGO, AND POSSIBLY OVER 100F FOR PORTIONS OF NORTH TEXAS AT THE
OUTSET OF WEEK-2. A DEVELOPING TROUGH OVER THE GREAT LAKES REDUCES POTENTIAL
FOR EXCESSIVE HEAT BY DAY-10 SO A SLIGHT RISK FOR EXCESSIVE HEAT IS POSTED FOR
PORTIONS OF THE MISSISSIPPI, TENNESSEE, AND OHIO VALLEYS, GREAT LAKES, AND
SOUTHEAST U.S. FOR AUG 29-30. THE PETS ALSO INDICATE A 20% PROBABILITY OF
MAXIMUM TEMPERATURES EXCEEDING THE 85TH PERCENTILE OVER PORTIONS OF THE DESERT
SOUTHWEST BUT ABSOLUTE TEMPERATURES ARE NOT EXPECTED TO EXCEED HAZARDOUS
THRESHOLDS FOR THE REGION, THUS NO ASSOCIATED HAZARD IS POSTED AT THIS TIME.
TROPICAL STORM GILMA IS AN ACTIVE TROPICAL CYCLONE (TC) LOCATED MORE THAN 2000
MILES EAST-SOUTHEAST OF HAWAII AND MOVING GENERALLY WEST IN THE CENTRAL
PACIFIC. CURRENTLY, THE NATIONAL HURRICANE CENTER (NHC) FORECASTS GILMA TO
CONTINUE TO TRACK ROUGHLY DUE WEST AND INITIALLY STRENGTHEN INTO A MAJOR
HURRICANE BEFORE WEAKENING AND APPROACHING THE HAWAIIAN ISLANDS EARLY IN
WEEK-2. THIS TC HAS THE POTENTIAL TO BRING HEAVY RAIN, STRONG WINDS, AND
DANGEROUS SURF. AREAS AFFECTED BY RECENT WILDFIRES WOULD ALSO BE AT ELEVATED
RISK FOR LANDSLIDES AND DEBRIS FLOWS. THERE IS STILL A GREAT DEAL OF
UNCERTAINTY REGARDING THE EVOLUTION OF GILMA BUT THE SITUATION WILL BE CLOSELY
MONITORED IN THE COMING DAYS.
MORE ZONAL MID-LEVEL FLOW OVER THE SOUTHERN TIER OF THE CONUS GENERALLY
DECREASES THE POTENTIAL FOR HEAVY PRECIPITATION. THE PETS DO INDICATE A 20%
CHANCE OF 3-DAY TOTAL PRECIPITATION EXCEEDING THE 85TH PERCENTILE FOR PORTIONS
OF THE GULF COAST AND EXTENDING WESTWARD INTO THE DESERT SOUTHWEST DUE TO AN
INCREASED POTENTIAL FOR SURFACE LOW AND/OR TROUGH DEVELOPMENT , BUT ABSOLUTE
RAINFALL TOTALS ARE NOT EXPECTED TO EXCEED HAZARDOUS THRESHOLDS SO NO HEAVY
PRECIPITATION HAZARD IS POSTED AT THIS TIME. THE ECMWF PET ALSO INDICATES A
SIMILAR POTENTIAL FOR HEAVY PRECIPITATION FOR PORTIONS OF ALASKA, BUT SIMILAR
TO THE GULF COAST, PRECIPITATION TOTALS ARE NOT EXPECTED TO EXCEED HAZARDOUS
THRESHOLDS SO NO ASSOCIATED HAZARD IS DESIGNATED.
THE ECMWF PET FOR MAXIMUM WIND SPEED INDICATES AT LEAST A 20% PROBABILITY FOR
WIND SPEEDS TO EXCEED THE 85TH PERCENTILE OVER THE FIRST HALF OF WEEK-2,
HOWEVER ABSOLUTE MAXIMUM VALUES FROM BOTH ECMWF AND GEFS FOR THE RELEVANT TIME
PERIOD DO NOT EXCEED HAZARDOUS THRESHOLDS SO NO ASSOCIATED HAZARD IS POSTED AT
THIS TIME.
BELOW-NORMAL RAINFALL ANTICIPATED OVER MUCH OF THE SOUTHERN PLAINS AND
MISSISSIPPI VALLEY DURING WEEK-2 COMBINED WITH AN INCREASED LIKELIHOOD OF
EXCESSIVE HEAT AND BELOW-NORMAL 30-DAY ACCUMULATED PRECIPITATION, RESULTS IN AN
ELEVATED RISK OF RAPID ONSET DROUGHT (ROD) ACROSS PORTIONS OF THE SOUTHERN
PLAINS AND PARTS OF THE MISSISSIPPI, TENNESSEE AND OHIO VALLEYS FURTHER
SUPPORTED BY DECLINING SOIL MOISTURE VALUES AND DRY CONDITIONS FAVORED OVER THE
NEXT TWO WEEKS.
FORECASTER: DANNY BARANDIARAN
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page