520
FXUS01 KWBC 190834
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
433 AM EDT WED JUL 19 2023
VALID 12Z WED JUL 19 2023 - 12Z FRI JUL 21 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 TODAY...
...TROPICAL STORM CALVIN WEAKENING ON APPROACH TO HAWAII THIS
MORNING, BUT HEAVY RAINS AND TROPICAL STORM FORCE WIND GUSTS STILL
EXPECTED...
...CANADIAN WILDFIRES/SMOKE RESPONSIBLE FOR AIR QUALITY ALERTS
OVER PARTS OF THE GREAT LAKES, SOUTHERN MID-ATLANTIC, AND
NORTHEAST TODAY...
A PROLONGED AND EXTREMELY DANGEROUS HEAT WAVE CONTINUES FOR MUCH
OF THE SOUTHERN TIER OF THE LOWER 48 THANKS TO AN EXPANSIVE DOME
OF HIGH PRESSURE ALOFT, WHERE OVER 80 MILLION PEOPLE ARE UNDER
EITHER AN EXCESSIVE HEAT WARNING/WATCH OR HEAT ADVISORY.
ADDITIONAL RECORD BREAKING HEAT IS EXPECTED 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. THESE EXCEPTIONALLY WARM OVERNIGHT
MINIMUMS 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 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. 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. THIS MORNING,
ONGOING ROUNDS OF THUNDERSTORMS CONTAINING PROLIFIC RAINFALL RATES
ARE RESPONSIBLE FOR THE AREAS OF SIGNIFICANT FLASH FLOODING IN
PARTS OF WESTERN KENTUCKY OVERNIGHT. THE WEATHER PREDICTION CENTER
MAINTAINS A MODERATE RISK FOR EXCESSIVE RAINFALL FROM WESTERN
KENTUCKY INTO NORTHWEST TENNESSEE. THERE ARE ALSO SLIGHT RISKS
FROM CENTRAL MISSOURI ON SOUTH AND EAST INTO THE HEART OF THE
TENNESSEE VALLEY, AS WELL AS SOUTHEAST VIRGINIA. FARTHER NORTH,
THE STORM PREDICTION CENTER (SPC) HAS ISSUED A SLIGHT RISK FROM
NORTHERN KANSAS ON NORTH AND WEST INTO THE UPPER MISSISSIPPI
VALLEY. SEVERE STORMS WITHIN THE SLIGHT RISK AREA COULD CONTAIN
VERY LARGE HAIL, AS WELL AS DAMAGING WIND GUSTS AND TORNADOES.
BOTH WPC AND SPC HAVE MARGINAL RISK AREAS IN THE CENTRAL HIGH
PLAINS AND OVER THE MID-ATLANTIC. 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 CAROLINAS. 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 HAVE
ENOUGH MONSOON MOISTURE TO WORK WITH THAT, WITH THE HELP OF STRONG
DAYTIME HEATING, SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED
THROUGH THE END OF THE WORK-WEEK.
IN THE NORTH CENTRAL PACIFIC OCEAN, TROPICAL STORM CALVIN IS
FORECAST TO CONTINUE WEAKENING AS IT TRACKS JUST SOUTH OF HAWAII'S
BIG ISLAND, WHERE TROPICAL STORM WARNINGS REMAIN IN PLACE. THE
LATEST FORECAST FROM THE CENTRAL PACIFIC HURRICANE CENTER SHOWS
THE STORM MAINTAINING TROPICAL STORM STATUS AS IT TRACKS SOUTH OF
THE BIG ISLAND TONIGHT. THE FORECAST IS STILL ON TRACK FOR CALVIN
TO PRODUCE HEAVY RAINFALL, WITH AS MUCH AS 4-8 INCHES AND
LOCALIZED AMOUNTS UP TO 10 INCHES ALONG THE WINDWARD SLOPES OF THE
BIG ISLAND. A LITTLE FARTHER NORTH, 3-6 INCHES OF RAINFALL ARE
POSSIBLE ALONG THE WINDWARD SLOPES OF MAUI. POTENTIAL IMPACTS
INCLUDE LOCALIZED FLASH FLOODING AND MUDSLIDES. CALVIN WILL ALSO
CAUSE ROUGH SEAS AND LOCALLY STRONG WINDS AROUND "THE ALOHA
STATE." SEE CENTRAL PACIFIC HURRICANE CENTER ADVISORIES ON CALVIN
FOR MORE INFORMATION ON THE STORM.
SMOKE FROM THE CANADIAN WILDFIRES ARE RESPONSIBLE FOR LINGERING
AIR QUALITY ALERTS THAT ARE IN PLACE FOR PORTIONS OF THE GREAT
LAKES, SOUTHERN MID-ATLANTIC, AND NORTHEAST. FORTUNATELY, SHORT
TERM FORECASTS SHOW LESSER CONCENTRATIONS OF CANADIAN WILDFIRE
SMOKE BEYOND THIS AFTERNOON. THIS SHOULD GIVE MOST OF THE NORTHERN
TIER OF THE U.S. A BREAK FROM THE MORE CONCENTRATED SMOKE PLUMES
THROUGH AT LEAST THURSDAY.
MULLINAX
GRAPHICS AVAILABLE AT
HTTPS://WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP
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