406
FXUS01 KWBC 180749
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
349 AM EDT TUE JUL 18 2023
VALID 12Z TUE JUL 18 2023 - 12Z THU JUL 20 2023
...LENGTHY & DANGEROUS HEAT WAVE TO CONTINUE IN THE SOUTHWEST,
SOUTH CENTRAL U.S., AND SOUTH FLORIDA...
...FLASH FLOODING & SEVERE WEATHER IN PORTIONS OF THE NATION'S
HEARTLAND AND THE EAST, HEADLINED BY A MODERATE RISK FOR EXCESSIVE
RAINFALL IN THE PARTS OF THE LOWER OHIO & TENNESSEE VALLEYS...
...TROPICAL STORM CALVIN WEAKENING ON APPROACH TO HAWAII, BUT
HEAVY RAINS AND TROPICAL STORM FORCE WIND GUSTS STILL EXPECTED...
...CANADIAN WILDFIRES/SMOKE RESPONSIBLE FOR AIR QUALITY ALERTS
OVER PARTS OF THE NORTHERN HIGH PLAINS, MIDWEST, GREAT LAKES, AND
NORTHEAST...
A PROLONGED HEAT WAVE CONTINUES THROUGH MID-WEEK FOR MUCH OF THE
SOUTHERN TIER OF THE LOWER 48 THANKS TO AN EXPANSIVE DOME OF HIGH
PRESSURE ALOFT. RECORD BREAKING HEAT IS EXPECTED IN THE FOUR
CORNERS STATES, TEXAS TO THE LOWER MISSISSIPPI VALLEY, AND SOUTH
FLORIDA EACH DAY. DAYTIME HIGHS WILL RESIDE IN THE TRIPLE DIGITS
IN THE DESERT SOUTHWEST AND TEXAS. THE GULF COAST AND MID-SOUTH
CAN EXPECT DAYTIME HIGHS IN THE UPPER 90S THAT COINCIDE WITH
OPPRESSIVELY HIGH DEW POINTS, RESULTING IN SWELTERING HEAT INDICES
BETWEEN 105-115F. DAILY LOW TEMPERATURES WILL REMAIN QUITE WARM,
BREAKING RECORD WARM DAILY MINIMUMS IN SOME AREAS, ALLOWING FOR
MINIMAL RELIEF FROM THE HEAT OVERNIGHT. AN EXPANSIVE AREA OF
EXCESSIVE HEAT WARNINGS AND HEAT ADVISORIES REMAINS IN THE
SOUTHWEST, SOUTHERN PLAINS, WESTERN AND CENTRAL GULF COAST, AND
EVEN PARTS OF SOUTH FLORIDA WHERE WELL ABOVE NORMAL SEA SURFACE
TEMPERATURES AND LIGHTER THAN NORMAL WINDS ARE CONTRIBUTING TO
STIFLING HEAT. PLEASE VISIT HEAT.GOV FOR MORE INFORMATION ON
IMPACTS FROM THE HEAT WAVE. THE NORTHEAST AND MID-ATLANTIC WILL
CONTINUE TO SEE HOT AND HUMID CONDITIONS THROUGH TUESDAY, WHILE A
COLD FRONTAL PASSAGE HELPS TO MAKE CONDITIONS A LITTLE LESS MUGGY
BY WEDNESDAY. TO THE WEST, A PAIR OF COLD FRONTS WILL PROVIDE THE
MIDWEST AND GREAT LAKES WITH COOLER THAN NORMAL TEMPERATURES. SOME
LOCATIONS IN THE UPPER MIDWEST WILL STRUGGLE TO GET OUT OF THE 70S
FOR HIGHS ON TUESDAY.
A STORMY COUPLE OF DAYS ARE ON TAP FROM THE MIDWEST TO THE OHIO
AND TENNESSEE VALLEYS. TODAY AND INTO TUESDAY NIGHT, A STATIONARY
FRONTAL BOUNDARY OVER THE MIDDLE MISSISSIPPI VALLEY WILL BE THE
FOCUS FOR STRONG-TO-SEVERE STORMS. THE STORM PREDICTION CENTER
(SPC) HAS A SLIGHT RISK (THREAT LEVEL 2/5) THAT STRETCHED FROM THE
KANSAS CITY AND ST. LOUIS METRO AREAS TO NORTHWEST TENNESSEE AND
WESTERN KENTUCKY. DAMAGING WIND GUSTS, LARGE HAIL, AND TORNADOES
ARE ALL POSSIBLE IN SEVERE STORMS. MEANWHILE, DEVELOPING
THUNDERSTORMS WILL CONTAIN COPIOUS AMOUNTS OF MOISTURE AND COULD
TRAIN OVER PARTS OF THE REGION, RESULTING POSSIBLY IN DANGEROUS
FLASH FLOODING. THE WEATHER PREDICTION CENTER HAS ISSUED A
MODERATE RISK (THREAT LEVEL 3/4) OF EXCESSIVE RAINFALL FROM THE
MISSISSIPPI-OHIO RIVER CONFLUENCE TO NORTHWEST TENNESSEE. THERE IS
ALSO A SLIGHT RISK (THREAT LEVEL 2/4) OF EXCESSIVE RAINFALL IN THE
NORTHEAST DUE TO MORE ROUNDS OF THUNDERSTORMS IN AREAS THAT
FEATURE HIGHLY SATURATED SOILS. SPC HAS ITS OWN SEPARATE SLIGHT
RISK AREA TODAY IN NORTH DAKOTA WHERE STORMS COULD PRODUCE VERY
LARGE HAIL. ON TUESDAY, MORE SHOWERS AND STORMS WILL FORM FROM THE
CENTRAL ROCKIES AND MIDWEST TO THE MID-ATLANTIC. SPC AND WPC BOTH
HAVE LARGE MARGINAL RISK AREAS IN PLACE, WHILE WPC DOES HAVE A
SLIGHT RISK IN THE TENNESSEE VALLEY AND SOUTHERN APPALACHIANS
WHERE THE THREAT FOR FLASH FLOODING IS GREATER. FURTHER WEST, THE
SOUTHWEST MONSOON IS SHOWING SIGNS OF LIFE WITH ROUNDS OF SHOWERS
AND STORMS POSSIBLE EACH DAY. THE STRONGEST STORMS COULD PRODUCE
FLASH FLOODING AND DAMAGING WIND GUSTS.
IN THE NORTH CENTRAL PACIFIC OCEAN, TROPICAL STORM CALVIN IS
WEAKENING AS IT APPROACHES HAWAII'S BIG ISLAND WHERE TROPICAL
STORM WARNINGS HAVE BEEN ISSUED. THE LATEST FORECAST FROM THE
CENTRAL PACIFIC HURRICANE CENTER SHOWS THE STORM MAINTAINING
TROPICAL STORM STATUS AS IT TRACKS SOUTH OF THE BIG ISLAND TUESDAY
NIGHT. CALVIN IS LIKELY TO PRODUCE LOCALLY 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.
CALVIN IS ALSO LIKELY TO CAUSE ROUGH SEAS AROUND "THE ALOHA
STATE." SEE CENTRAL PACIFIC HURRICANE CENTER ADVISORIES ON CALVIN
FOR MORE INFORMATION ON THE STORM.
SMOKE FROM THE CANADIAN WILDFIRES WILL REMAIN IN THE PICTURE
THROUGH MID-WEEK AS NORTHWESTERLY WINDS ALOFT THAT ORIGINATE OVER
CANADA CONTINUE TO DIRECT SMOKE INTO THE LOWER 48. THERE ARE AIR
QUALITY ALERTS ISSUED FOR AREAS THE INCLUDE THE NORTHERN HIGH
PLAINS, THE MIDWEST, GREAT LAKES, SOUTHERN MID-ATLANTIC, AND INTO
THE NORTHEAST WHERE HIGHER CONCENTRATIONS OF SMOKE WILL RESULT IN
UNHEALTHY AIR QUALITY FOR SENSITIVE GROUPS.
MULLINAX
GRAPHICS AVAILABLE AT
HTTPS://WWW.WPC.NCEP.NOAA.GOV/BASICWX/BASICWX_NDFD.PHP
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