781
FXUS21 KWNC 201816
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 20 2024
SYNOPSIS: MODEL ENSEMBLES DEPICT HIGH PRESSURE BOTH AT THE SURFACE AND
MID-LEVELS ACROSS MUCH OF THE CONTIGUOUS U.S. (CONUS) THROUGHOUT THE FORECAST
PERIOD, LEADING TO THE POTENTIAL FOR EXCESSIVE HEAT FOR PORTIONS OF THE GREAT
PLAINS AND THE OHIO AND MISSISSIPPI VALLEYS, WITH THIS RISK POSSIBLY SHIFTING
EASTWARD EARLY IN WEEK-2. PROLONGED RAINFALL DEFICITS AND CONTINUED HEAT
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 CENTRAL PLAINS, WED-THU, AUG 28-29.
RISK FOR RAPID ONSET DROUGHT FOR PORTIONS OF THE SOUTHERN PLAINS, AND LOWER AND
MIDDLE MISSISSIPPI VALLEY.
DETAILED SUMMARY
FOR FRIDAY AUGUST 23 - TUESDAY AUGUST 27:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR WEDNESDAY AUGUST 28 - TUESDAY SEPTEMBER 03: TODAY’S MODEL SOLUTIONS FOR 500
HPA HEIGHTS AND ANOMALIES DEPICT BROAD RIDGING OVER THE CONUS AT THE OUTSET OF
WEEK-2 WITH A 594 DM MAXIMUM OVER THE DESERT SOUTHWEST. 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 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 GRAND RAPIDS, 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-11 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 28-29. THE PETS ALSO INDICATE A 20%
PROBABILITY OF MAXIMUM TEMPERATURES EXCEEDING THE 90TH 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.
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 TROPICAL CONVECTION, 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