304
FXUS01 KWBC 272006
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
405 PM EDT FRI SEP 27 2024
VALID 00Z SAT SEP 28 2024 - 00Z MON SEP 30 2024
...LIFE-THREATENING, CATASTROPHIC FLASH AND URBAN FLOODING ONGOING
IN THE SOUTHERN APPALACHIANS DUE TO RAINFALL FROM HELENE...
...RISK OF HEAVY RAINFALL LEADING TO SCATTERED INSTANCES OF FLASH
FLOODING AS WELL AS HIGH WINDS CONTINUES THROUGH TONIGHT FOR
PORTIONS OF THE SOUTHEAST AND OHIO/TENNESSEE VALLEYS...
...HEAVY RAINFALL AND ISOLATED FLASH FLOODING DUE TO POST TROPICAL
STORM HELENE FOR PORTIONS OF THE OHIO/TENNESSEE VALLEYS SATURDAY...
...WELL ABOVE AVERAGE TEMPERATURES AND SUMMER-LIKE HEAT EXPECTED
FROM THE SOUTHWEST TO THE NORTHERN PLAINS THIS WEEKEND WITH
NUMEROUS RECORD TYING/BREAKING HIGHS POSSIBLE...
NOW POST-TROPICAL STORM HELENE CONTINUES TO MOVE THROUGH THE
SOUTHEAST AND INTO THE TENNESSEE/OHIO VALLEYS THIS AFTERNOON WITH
A BROAD SWATH OF RAIN STRETCHING FROM THE MID-SOUTH EAST THROUGH
THE OHIO/TENNESSEE VALLEYS AND INTO THE CENTRAL APPALACHIANS AS
WELL AS THE SOUTHERN MID-ATLANTIC/CAROLINAS. WHILE RAINFALL HAS
TRENDED DOWN OVERALL, OR HAS COMPLETELY ENDED FOR SOME LOCATIONS
OVER PORTIONS OF THE SOUTHERN APPALACHIANS, LIFE-THREATENING,
CATASTROPHIC FLASH AND URBAN FLOODING CONTINUES. THERE HAVE BEEN
NUMEROUS HIGH-WATER RESCUES, ROADS CLOSED, AND AT LEAST ONE DAM
FAILURE. THE THREAT FOR FLOODING WILL ALSO CONTINUE AS RIVER
LEVELS REMAIN AT HIGH TO POTENTIALLY RECORD-BREAKING LEVELS.
ADDITIONAL LOCALLY HEAVY RAINFALL ON TOP OF ALREADY VERY WET
ANTECEDENT CONDITIONS ELSEWHERE ACROSS THE REGION WILL CONTINUE
INTO THE EVENING, BRINGING THE THREAT FOR ADDITIONAL SCATTERED
INSTANCES OF FLASH FLOODING. A BROAD SLIGHT RISK (LEVEL 2/4) OF
EXCESSIVE RAINFALL REMAINS IN PLACE. STRONG, POTENTIALLY DAMAGING
WIND GUSTS WILL ALSO CONTINUE INTO THE EVENING/EARLY OVERNIGHT
HOURS AS WELL. THERE IS A POSSIBILITY OF LONG-DURATION POWER
OUTAGES IN PORTIONS OF THE SOUTHEAST FOLLOWING THE STORM.
REMEMBER, IF YOU USE A GENERATOR, BE SURE IT IS PLACED OUTSIDE AT
LEAST 20 FEET AWAY FROM DOORS, WINDOWS, AND GARAGES TO AVOID
DEADLY CARBON MONOXIDE POISONING. THE STORM PREDICTION CENTER HAS
ALSO OUTLINED PORTIONS OF SOUTHEASTERN VIRGINIA AND NORTH CAROLINA
WITH SLIGHT (LEVEL 2/5) TO ENHANCED (LEVEL 3/5) RISKS OF SEVERE
WEATHER MAINLY FOR THE THREAT OF TORNADOES.
POST-TROPICAL STORM HELENE AND AN UPPER-LOW THAT HAS BEEN
LINGERING OVER THE MISSISSIPPI VALLEY WILL BEGIN TO INTERACT AND
BRING ADDITIONAL LOCALLY HEAVY RAINFALL TO PORTIONS OF THE OHIO
AND TENNESSEE VALLEYS ON SATURDAY, WITH SOME ISOLATED FLASH
FLOODING REMAINING POSSIBLE. THE RAINFALL WILL BEGIN TO REDUCE IN
COVERAGE AND SHIFT EASTWARD ON SUNDAY AS THE UPPER-LOW MEANDERS
EASTWARD, WITH SOME ISOLATED FLASH FLOODING POSSIBLE IN THE
CENTRAL APPALACHIANS. A LOCALLY HIGHER THREAT COULD MATERIALIZE IF
STORM COVERAGE/DURATION OVERLAPS AREAS OF WETTER ANTECEDENT
CONDITIONS FROM THE PRIOR DAYS RAINFALL DUE TO THE STORM, WITH
ADDITIONAL SLIGHT RISKS NOT OUT OF THE QUESTION. ADDITIONAL
MODERATE RAINFALL IS EXPECTED AHEAD OF A LINGERING
QUASI-STATIONARY FRONTAL BOUNDARY THROUGH THE MID-ATLANTIC THIS
WEEKEND, THOUGH AMOUNTS HERE SHOULD REMAIN LIGHTER. SHOWERS AND
THUNDERSTORMS WITH LOCALLY HEAVY RAINFALL ARE ALSO EXPECTED AHEAD
OF A STALLING COLD FRONT OVER THE FLORIDA PENINSULA, WITH SOME
ISOLATED FLASH FLOODING POSSIBLE. THE REST OF THE COUNTRY WILL BE
MOSTLY DRY THROUGH THE WEEKEND.
MUCH ABOVE AVERAGE, SUMMER-LIKE HEAT CONTINUES UNDER THE INFLUENCE
OF A BROAD UPPER-LEVEL RIDGE OVER THE WESTERN/CENTRAL U.S.,
PARTICULARLY FOR THE DESERT SOUTHWEST, GREAT BASIN, AND NORTHERN
PLAINS. EXCESSIVE HEAT WARNINGS ARE IN PLACE IN THE DESERT
SOUTHWEST AS HIGHS WILL SOAR INTO THE 110S. FORECAST HIGHS ARE IN
THE MID-80S TO MID-90S OVER MUCH OF THE NORTHERN PLAINS AND GREAT
BASIN, IN SOME CASES UPWARDS OF 20-30 DEGREES ABOVE AVERAGE.
NUMEROUS POTENTIALLY RECORD-TYING/BREAKING HIGHS ARE POSSIBLE. A
PACIFIC SYSTEM MOVING INTO THE NORTHWEST WILL BRING TEMPERATURES
DOWN TO AVERAGE FOR THE NORTHERN GREAT BASIN SUNDAY. WHILE NOT
QUITE AS WARM, CONDITIONS WILL ALSO BE ABOVE AVERAGE FOR THE
UPPER-MIDWEST AS HIGHS REACH INTO THE UPPER 70S TO MID-80S.
ELSEWHERE, HOT, HUMID CONDITIONS WILL CONTINUE AHEAD OF A COLD
FRONT IN SOUTH FLORIDA.
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