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FXUS21 KWNC 191923
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT AUGUST 19 2024
SYNOPSIS: MODEL ENSEMBLES DEPICT HIGH PRESSURE BOTH AT THE SURFACE AND
MID-LEVELS ACROSS MUCH OF THE CONTIGUOUS U.S. (CONUS) THROUGHOUT THE WEEK-2
PERIOD, LEADING TO THE POTENTIAL FOR EXCESSIVE HEAT FOR PORTIONS OF THE GREAT
PLAINS AND THE OHIO AND MISSISSIPPI VALLEYS. 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, TUE-FRI, AUG 17-30.
RISK FOR RAPID ONSET DROUGHT FOR PORTIONS OF THE SOUTHERN PLAINS, AND LOWER AND
MIDDLE MISSISSIPPI VALLEY.
DETAILED SUMMARY
FOR THURSDAY AUGUST 22 - MONDAY AUGUST 26:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY AUGUST 27 - MONDAY SEPTEMBER 02: TODAY’S MODEL SOLUTIONS FOR 500
HPA HEIGHTS AND ANOMALIES DEPICT GENERALLY ZONAL FLOW AND 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 CENTRAL PLAINS FOR AUG 27-30. 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.
ZONAL MID-LEVEL FLOW OVER 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 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.
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 MISSISSIPPI VALLEY FURTHER SUPPORTED BY DECLINING SOIL MOISTURE
VALUES AND DRY CONDITIONS FAVORED OVER THE NEXT TWO WEEKS. WITH RECENT AND
CONTINUING HOT AND DRY CONDITIONS, THE ROD RISK AREA HAS BEEN SLIGHTLY EXPANDED
SOUTHWARD, AS WELL AS NORTHWARD ALONG THE MISSISSIPPI VALLEY INTO SOUTHERN
ILLINOIS AND INDIANA.
FORECASTER: DANNY BARANDIARAN
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