057
FXUS01 KWBC 210801
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
400 AM EDT FRI JUN 21 2024
VALID 12Z FRI JUN 21 2024 - 12Z SUN JUN 23 2024
...RECORD HOT TEMPERATURES CONTINUE OVER PORTIONS OF THE
MIDWEST/OHIO VALLEY WHILE EXPANDING OVER THE MID-ATLANTIC...
...HEAVY RAIN AND FLASH FLOODING CONCERNS ACROSS THE UPPER MIDWEST
FRIDAY AND GREAT LAKES SATURDAY...
..RISK FOR FLASH FLOODING IN THE FOUR CORNERS REGION FRIDAY
..HEAT BUILDING OVER MUCH OF THE WEST HEADING INTO THE WEEKEND
A STUBBORN UPPER-LEVEL HIGH OVER PORTIONS OF THE EASTERN TO
SOUTH-CENTRAL U.S. WILL GENERALLY REMAIN IN PLACE, CONTINUING A
HEAT WAVE OVER THE REGION WITH THE FOCUS FOR THE MOST INTENSE HEAT
OVER PORTIONS OF THE MIDWEST/OHIO VALLEY AND EXPANDING IN THE
MID-ATLANTIC. FORECAST TEMPERATURES GENERALLY IN THE MID-90S
FRIDAY WILL RISE INTO THE UPPER 90S TO 100 SATURDAY IN THE
MID-ATLANTIC, WITH RECORD-TYING/BREAKING TEMPERATURES POSSIBLE.
HEAT-RELATED ADVISORIES AND WARNINGS ARE IN PLACE AS THESE
TEMPERATURES, WHEN COMBINED WITH THE HUMIDITY, WILL BRING HEAT
INDEX VALUES INTO THE 100-105 DEGREE RANGE, WITH VALUES AS HIGH AS
110 POSSIBLE THROUGH THE SOUTHERN MID-ATLANTIC ON SATURDAY.
ADDITIONALLY, OVERNIGHT LOW TEMPERATURES WILL REMAIN IN THE
MID-70S FOR MANY LOCATIONS, AT POTENTIAL RECORD-TYING/BREAKING
LEVELS, PROVIDING LITTLE RELIEF FROM THE HEAT OVERNIGHT. THE EARLY
ARRIVAL OF THIS HEAT IN THE SUMMER SEASON, PERSISTENCE OVER
MULTIPLE DAYS, AND ABUNDANT SUNSHINE WILL AGGRAVATE HEAT STRESS ON
THOSE WITHOUT RELIABLE AIR CONDITIONING. TEMPERATURES MORE BROADLY
FROM THE EAST COAST TO THE CENTRAL/SOUTHERN PLAINS WILL BE IN THE
LOW 90S FRIDAY AND MID-90S SATURDAY. MEANWHILE, RELIEF CONTINUES
TO THE NORTH OF A FRONTAL BOUNDARY DRAPED THOUGH SOUTHERN NEW
ENGLAND, WITH HIGHS NOW MOSTLY IN THE 70S AND LOW 80S.
MEANWHILE, AREAS OF SHOWERS AND THUNDERSTORMS WILL CONTINUE ALONG
THIS FRONTAL BOUNDARY TO THE NORTH OF THE UPPER-HIGH, AS MOISTURE
FROM THE GULF FLOWS NORTHWARD THROUGH THE PLAINS AND AROUND
EASTWARD THROUGH THE UPPER GREAT LAKES AND INTO NEW ENGLAND. THE
GREATEST THREAT FOR SIGNIFICANT HEAVY RAINFALL WILL BE AHEAD OF A
SURFACE WAVE OVER PORTIONS OF THE UPPER MIDWEST AS OVERNIGHT STORM
COMPLEXES HELP PRIME THE SOILS THURSDAY NIGHT/FRIDAY MORNING AHEAD
OF ANOTHER ROUND OF STORMS EXPECTED LATER FRIDAY. A MODERATE RISK
OF EXCESSIVE RAINFALL (LEVEL 3/4) IS IN EFFECT FRIDAY CENTERED ON
SOUTHERN MINNESOTA AND ADJACENT WEST-CENTRAL WISCONSIN, NORTHERN
IOWA, AND SOUTHEASTERN SOUTH DAKOTA, WHERE THE HIGHEST POTENTIAL
FOR HEAVY DOWNPOURS, SEVERAL INCHES OF RAINFALL, AND SCATTERED TO
NUMEROUS INSTANCES OF FLASH FLOODING EXISTS. ADDITIONAL SCATTERED
INSTANCES OF FLASH FLOODING WILL BE POSSIBLE MORE BROADLY ACROSS
THE UPPER MIDWEST. A FEW SEVERE THUNDERSTORMS ARE EXPECTED AS
WELL, AS THE STORM PREDICTION CENTER HAS INCLUDED A SLIGHT RISK OF
SEVERE WEATHER (LEVEL 2/5) FOR THE REGION, EXTENDING SOUTHWESTWARD
INTO THE CENTRAL PLAINS AND THE NORTHWESTWARD INTO THE
CENTRAL/NORTHERN HIGH PLAINS. DAMAGING WINDS, LARGE HAIL, AND A
FEW TORNADOES ARE ALL POSSIBLE. AN UPPER-LEVEL SHORTWAVE
APPROACHING FROM THE WEST WILL HELP TO DEEPEN THE FRONTAL WAVE AND
PUSH THE SYSTEM EASTWARD ON SATURDAY, BRINGING THE THREAT FOR
HEAVY RAINFALL TO PORTIONS OF THE GREAT LAKES SOUTHWESTWARD INTO
THE UPPER MISSISSIPPI VALLEY. A SLIGHT RISK OF EXCESSIVE RAINFALL
(LEVEL 2/4) IS IN PLACE SATURDAY AS AN ORGANIZED COMPLEX OF STORMS
IS EXPECTED TO FOLLOW THE SYSTEM EASTWARD, BRINGING ADDITIONAL
LOCALLY HEAVY RAINFALL AND SCATTERED INSTANCES OF FLASH FLOODING.
SOME SEVERE THUNDERSTORMS WILL AGAIN BE POSSIBLE WITH A SLIGHT
RISK IN PLACE MAINLY FOR THE THREAT OF DAMAGING WINDS.
AN UPPER-LEVEL TROUGH MOVING OVER THE SOUTHWEST WILL BRING AREAS
OF SHOWERS AND THUNDERSTORMS TO THE FOUR CORNERS REGION ON
SATURDAY. ANOMALOUSLY HIGH MOISTURE SPREADING INTO THE REGION FROM
THE REMNANTS OF FORMER T.S. ALBERTO WILL HELP CONTRIBUTE TO
LOCALLY HEAVY DOWNPOURS AND THE THREAT FOR FLASH FLOODING, WITH A
SLIGHT RISK OF EXCESSIVE RAINFALL IN EFFECT FRIDAY. THE FOCUS FOR
STORMS SHOULD SHIFT MORE INTO PORTIONS OF THE DESERT SOUTHWEST ON
SATURDAY, WITH A LINGERING THREAT OF SOME ISOLATED FLASH FLOODING.
AS THIS TROUGH MOVES EASTWARD, A RIDGE WILL BEGIN TO BUILD OVER
THE WEST IN ITS WAKE, BRINGING AND EXPANDING AREA OF HOT, ABOVE
AVERAGE SUMMER TEMPERATURES. FORECAST HIGHS IN THE 90S ON FRIDAY
WILL SOAR INTO THE 100S ON SATURDAY FOR PORTIONS OF THE GREAT
BASIN AND CENTRAL CALIFORNIA VALLEYS. HEAT-RELATED ADVISORIES AND
WATCHES HAVE BEEN ISSUED FOR THE CENTRAL VALLEYS SOUTH INTO
INTERIOR SOUTHERN CALIFORNIA BEGINNING SATURDAY. CONDITIONS WILL
ALSO BE NOTABLY HOT OVER THE DESERT SOUTHWEST ON FRIDAY,
PARTICULARLY OVER CENTRAL ARIZONA WHERE EXCESSIVE HEAT WARNINGS
ARE IN PLACE, WITH HIGHS INTO THE 110S. THE NOTED INCREASING
MOISTURE/STORM CHANCES WILL HELP COOL TEMPERATURES DOWN A FEW
DEGREES SATURDAY. ELSEWHERE, A COUPLE OF WAVES OF LOW PRESSURE
WILL PASS OVER PORTIONS OF THE SOUTHEAST/FLORIDA AS WELL AS SOUTH
TEXAS, WITH DAILY THUNDERSTORMS CHANCES FRIDAY AND SATURDAY.
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