185
FXUS01 KWBC 230735
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
334 AM EDT WED AUG 23 2023
VALID 12Z WED AUG 23 2023 - 12Z FRI AUG 25 2023
...OVER 100 MILLION PEOPLE UNDER HEAT ALERTS FROM THE MIDWEST TO
THE GULF COAST AS RECORD-BREAKING TEMPERATURES CONTINUE THROUGH
THE END OF THE WEEK...
...SCATTERED FLASH FLOODING THREAT SPANS ACROSS WEST TEXAS, THE
SOUTHWEST, AND CENTRAL GREAT BASIN OVER THE NEXT FEW DAYS...
...LOCALLY HEAVY RAIN AND SEVERE THUNDERSTORMS POSSIBLE ACROSS THE
LOWER GREAT LAKES AND UPPER OHIO VALLEY...
A SEARING AUGUST HEAT WAVE IS FORECAST TO CONTINUE THROUGH AT
LEAST THE END OF THIS WEEK UNDERNEATH A POTENT UPPER-LEVEL RIDGE
ANCHORED OVER THE MID-MISSISSIPPI VALLEY, WHICH WILL DRIVE
OPPRESSIVE HEAT FROM THE CENTRAL U.S. TO GULF COAST STATES. HIGH
TEMPERATURES THROUGHOUT THESE AREAS ARE FORECAST TO REACH INTO THE
UPPER 90S AND LOW 100S THROUGH THURSDAY BEFORE A COLD FRONT
DROPPING SOUTH BEGINS TO USHER IN COOLER TEMPERATURES OVER THE
UPPER MIDWEST ON FRIDAY. WHEN FACTORING IN BRUTAL HUMIDITY LEVELS,
MAXIMUM HEAT INDICES COULD APPROACH 120 DEGREES. WHILE IT IS NOT
UNCOMMON FOR AUGUST TO FEATURE DANGEROUS HEAT, THESE TEMPERATURES
ARE EXTREMELY ANOMALOUS AND LIKELY TO BREAK NUMEROUS DAILY AND
POTENTIALLY MONTHLY RECORDS. IN FACT, HIGHS ARE FORECAST TO REACH
UP TO 20 DEGREES ABOVE AVERAGE THROUGHOUT IOWA AND NEIGHBORING
STATES TODAY. VERY WARM OVERNIGHT TEMPERATURES ONLY DROPPING INTO
THE UPPER 70S AND LOW 80S WILL COMPOUND THE IMPACTS ASSOCIATED
WITH THIS POTENTIALLY DEADLY HEAT WAVE. HEAT ALERTS (EXCESSIVE
HEAT WARNINGS, WATCHES, AND ADVISORIES) HAVE BEEN ISSUED FROM
MINNEAPOLIS TO NEW ORLEANS, WHICH INCLUDES 22 STATES AND ROUGHLY
130 MILLION PEOPLE. IT IS IMPERATIVE TO TAKE THE HEAT SERIOUSLY
AND AVOID EXTENDED TIME OUTDOORS, AS TEMPERATURES AND HEAT INDICES
WILL REACH LEVELS THAT WOULD POSE A HEALTH RISK, AND BE
POTENTIALLY DEADLY TO ANYONE WITHOUT EFFECTIVE COOLING AND/OR
ADEQUATE HYDRATION. REMEMBER, HEAT IS THE
NUMBER-ONE-WEATHER-RELATED CAUSE OF DEATH IN THE UNITED STATES.
MEANWHILE, TROPICAL DEPRESSION HAROLD AND ITS SURROUNDING MOISTURE
IS CURRENTLY PUSHING WESTWARD ACROSS FAR NORTHERN MEXICO AND IS
EXPECTED TO PRODUCE THE POTENTIAL FOR FLASH FLOODING FROM WEST
TEXAS TO THE SOUTHWEST TODAY. AS THE SHOWERS AND THUNDERSTORMS
CONTINUE TO CIRCLE AROUND THE ANCHORED UPPER HIGH IN THE CENTRAL
U.S., THE REMNANT TROPICAL MOISTURE IS FORECAST TO TURN NORTH AND
ENTER THIS PART OF THE COUNTRY FROM NORTH-CENTRAL MEXICO, WHILE
ALSO PUSHING INTO THE CENTRAL GREAT BASIN ON FRIDAY. THUNDERSTORMS
WILL BE CAPABLE OF CONTAIN INTENSE RAINFALL RATES THAT COULD LEAD
TO RAPID RUNOFF AND FLOODING CONCERNS. TO FURTHER HIGHLIGHT THE
THREAT, A SLIGHT RISK (LEVEL 2/4) OF EXCESSIVE RAINFALL HAS BEEN
ISSUED FROM WEST TEXAS TO SOUTHERN NEW MEXICO TODAY AND SOUTHERN
UTAH ON THURSDAY. LINGERING ANOMALOUS ATMOSPHERIC MOISTURE CONTENT
AND AN APPROACHING COLD FRONT WILL COMBINE TO PRODUCE ADDITIONAL
SCATTERED FLASH FLOODING CHANCES OVER PARTS OF THE CENTRAL
ROCKIES/HIGH PLAINS ON FRIDAY.
ELSEWHERE, PRECIPIATION CHANCES CONTINUE TO CIRCUMVENT THE STRONG
UPPER HIGH OVER THE MIDWEST AND PROGRESS FROM THE GREAT LAKES TO
THE OHIO VALLEY/CENTRAL APPALACHIANS TODAY. SOME OF THE STRONGEST
THUNDERSTORMS COULD YIELD ISOLATED INSTANCES OF FLASH FLOODING,
DAMAGING WIND GUSTS, AND SEVERE HAIL. RAIN AND THUNDERSTORM
CHANCES WILL CONTINUE TOWARDS THE END OF THE WEEK WHILE ALSO
PROGRESSING EASTWARD TOWARDS THE MID-ATLANTIC AND NORTHEAST.
SNELL
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