870
FXUS01 KWBC 192001
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
400 PM EDT WED JUL 19 2023
VALID 00Z THU JUL 20 2023 - 00Z SAT JUL 22 2023
...LENGTHY & DANGEROUS HEAT WAVE TO CONTINUE ACROSS THE SOUTHERN
TIER THIS WEEK...
...FLASH FLOODING & SEVERE WEATHER POSSIBLE FROM THE NATION'S
HEARTLAND TO THE MID-ATLANTIC THROUGH THURSDAY, HEADLINED BY A
MODERATE RISK IN WESTERN KENTUCKY AND NORTHWEST TENNESSEE...
...TROPICAL STORM CALVIN WEAKENING ON APPROACH TO HAWAII THIS
MORNING, BUT HEAVY RAINS AND TROPICAL STORM FORCE WIND GUSTS STILL
EXPECTED...
LITTLE CHANGE TO THE OVERALL MESSAGE REGARDING A PROLONGED AND
EXTREMELY DANGEROUS HEAT WAVE ONGOING OVER MUCH OF THE SOUTHERN
TIER OF THE LOWER 48, WHERE AROUND 80 MILLION PEOPLE REMAIN UNDER
A EXCESSIVE HEAT WARNING/WATCH OR HEAT ADVISORY. DOZENS OF HIGH
TEMPERATURE RECORDS COULD FALL ACROSS THE FOUR CORNERS STATES,
TEXAS TO THE LOWER MISSISSIPPI VALLEY, AND SOUTH FLORIDA THROUGH
THE END OF THE WORK WEEK. DAYTIME HIGHS WILL RESIDE IN THE TRIPLE
DIGITS IN THE DESERT SOUTHWEST AND SOUTHERN PLAINS TODAY, WHILE
THE GULF COAST AND MID-SOUTH CAN EXPECT DAYTIME HIGHS IN THE UPPER
90S THAT COINCIDE WITH OPPRESSIVELY HIGH DEW POINTS THROUGH
THURSDAY, RESULTING IN SWELTERING HEAT INDICES AS HIGH AS 120
DEGREES IN SOME AREAS. MEANWHILE, DAILY LOW TEMPERATURES WILL
REMAIN QUITE WARM WITH BREAKING RECORD WARM DAILY MINIMUMS
EXPECTED, WHICH WILL LIMIT RELIEF FROM THE HEAT OVERNIGHT. EVEN
PARTS OF SOUTH FLORIDA WILL CONTINUE TO CONTEND WITH STIFLING HEAT
THANKS IN LARGE PART TO WELL ABOVE NORMAL SEA SURFACE TEMPERATURES
AND LIGHTER THAN NORMAL WINDS ACROSS THE SUNSHINE STATE. PLEASE
VISIT HEAT.GOV, AND THE KEY MESSAGES ISSUED BY THE WEATHER
PREDICTION CENTER AND CLIMATE PREDICTION CENTER FOR MORE
INFORMATION ON IMPACTS FROM THE HEAT WAVE. THE MID-ATLANTIC WILL
CONTINUE TO SEE THE USUAL HOT AND MUGGY CONDITIONS FOR MID-JULY
WHILE THE NORTHEAST REMAINS IN THE 80S BUT DEALS WITH LESS HUMID
CONDITIONS COMPARED TO THEIR NEIGHBORS TO THE SOUTH. TO THE WEST,
A PAIR OF COLD FRONTS WILL PROVIDE THE UPPER MIDWEST AND BOTH THE
NORTHERN AND CENTRAL HIGH PLAINS WITH COOLER THAN NORMAL
TEMPERATURES. IN FACT, SOME LOCATIONS IN THE NORTHERN AND CENTRAL
HIGH PLAINS WILL STRUGGLE TO GET OUT OF THE 70S FOR THROUGH
MIDWEEK.
THE AFOREMENTIONED COLD FRONTS THAT ARE USHERING IN COOLER AND
MORE REFRESHING TEMPERATURES INTO THE NORTH CENTRAL U.S. ARE ALSO
TO BLAME FOR ROUNDS TO STRONG-TO-SEVERE STORMS FROM THE CENTRAL
ROCKIES AND GREAT PLAINS, TO THE MID-ATLANTIC COAST. SINCE THIS
MORNING, CATASTROPHIC FLOODING OCCURRED ACROSS PORTIONS OF WESTERN
KENTUCKY WHERE PRELIMINARY REPORTS SHOW OVER 10" OF RAINFALL SINCE
MIDNIGHT ACROSS FAR WESTERN PORTIONS OF THE STATE FROM A
PERSISTENT BAND OF TRAINING THUNDERSTORMS. FORTUNATELY, THE
PROLIFIC RAINFALL EVENT IS GENERALLY ON A DOWNWARD TREND, ALTHOUGH
A MODERATE RISK OF EXCESSIVE RAINFALL REMAINS AS ANY ADDITIONAL
RAINFALL WILL QUICKLY TRANSLATE TO RUNOFF OVER AREAS HIT HARD
EARLIER TODAY. MEANWHILE, A SLIGHT RISK OF EXCESSIVE RAINFALL ALSO
EXTENDS INTO EASTERN TENNESSEE, WITH A SEPARATE AREA ALSO
HIGHLIGHTED ACROSS SOUTHEAST VIRGINIA/NORTHEAST NORTH CAROLINA.
HEAVY RAIN ASIDE, THE STORM PREDICTION CENTER (SPC) HAS ISSUED A
SLIGHT RISK OF SEVERE WEATHER TODAY ACROSS THE CENTRAL PLAINS INTO
THE UPPER MIDWEST, AND OVER SOUTHEAST VIRGINIA/NORTHEAST NORTH
CAROLINA FOR SOME TORNADOES, HAIL, AND WIND. BY THURSDAY, THE
SEVERE WEATHER AND EXCESSIVE RAINFALL THREAT EXPANDS TO INCLUDE
THE CENTRAL HIGH PLAINS, PORTIONS OF THE GREAT LAKES, THE CENTRAL
APPALACHIANS, AND THE TENNESSEE VALLEY. IN THESE REGIONS,
THUNDERSTORMS COULD PRODUCE ANY COMBINATION OF DAMAGING WIND
GUSTS, LARGE HAIL, TORNADOES, OR FLASH FLOODING. FARTHER WEST, THE
ROCKIES AND SOUTHWEST WILL ALSO HAVE ENOUGH MONSOON MOISTURE TO
WORK WITH TO FUEL SCATTERED SHOWERS AND THUNDERSTORMS THROUGH THE
END OF THE WORK-WEEK.
IN THE NORTH CENTRAL PACIFIC OCEAN, TROPICAL STORM CALVIN WILL
CONTINUE TO WEAKEN AS IT DRIFTS WEST OF THE HAWAIIAN ISLANDS TODAY
AND TONIGHT, ALTHOUGH SOME PERIPHERAL IMPACTS (INCLUDING DANGEROUS
SURF AND DAMAGING WINDS) WILL REMAIN. THROUGH TOMORROW, RAINFALL
AMOUNTS UPWARDS OF 4-8" (LOCALLY UP TO 10") ARE POSSIBLE ALONG THE
WINDWARD SLOPES OF THE BIG ISLAND OF HAWAII, WHICH COULD LEAD TO
LOCALIZED FLASH FLOODING AND MUDSLIDES. SEE CENTRAL PACIFIC
HURRICANE CENTER ADVISORIES ON CALVIN FOR MORE INFORMATION ON THE
STORM.
ASHERMAN/MULLINAX
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