Fast Facts:
MEMPHIS, Tenn. – With the potential for once-in-a-lifetime rainfall and widespread impacts, "generational flooding" is possible across parts of the nation through Saturday, fueled by repeated rounds of storms that are already underway. The initial wave of storms was part of the same system that brought a deadly tornado outbreak Wednesday to parts of Arkansas, Missouri, Tennessee and Kentucky.
A stalled front is hanging over the central U.S. and bringing a series of widespread thunderstorms with drenching rain forecast to last through Saturday.
"This isn’t routine," the National Weather Service in Memphis, Tennessee, warned, noting that five-day total rainfall amounts are in the 10- to 15-inch range along and north of Interstate 40 in West Tennessee. "This is not your average flood risk. Generational flooding with devastating impacts is possible."
A "Particularly Dangerous Situation" Flood Watch is in effect through Sunday morning for portions of southern Illinois, southwestern Indiana, western Kentucky and southeastern Missouri.
Governors in Tennessee, Kentucky and Arkansas have all declared states of emergency due to flooding and severe weather damage.
Flooding was underway Thursday morning in Nashville, Tennessee. Cars were seen stuck in floodwaters in South Nashville in the early-morning hours.
By daylight Thursday, neighborhoods were already inundated. The Trace Creek in the Bellevue neighborhood was well out of its banks.
The Nashville Fire Department performed water rescues Thursday morning. Numerous roads in the metro area were closed due to flooding.
The NWS in Little Rock, Arkansas, strongly advised motorists to find an alternative route if they encounter a flooded road or high water. The force of the water can easily carry away a vehicle, and the road surface beneath the water may be damaged or completely washed out.
"River flooding will likely become an issue as well," the agency stressed. "It is absolutely imperative to stay up to date to the latest NWS forecast with regards to severe weather hazards and severe hydrologic hazards!"
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The forecast heavy rainfall in this event has a return interval of anywhere from 25 to 100 years.
"In other words, a heavy rainfall event of this magnitude falling within four days is an event that happens once in a generation to once in a lifetime," the NWS in Little Rock noted.
NOAA's Weather Prediction Center (WPC) encouraged many to prepare if they live in a flood zone anywhere from Arkansas, northeast through the Ohio and Tennessee valleys.
"Anyone surrounding will want to monitor this setup closely as small changes could have heightened impacts given the forecasted setup," the WPC warned. "Be sure to stay up to date for the latest changes as we move through the remainder of the week as this pattern remains very active and prone to significant life-threatening flash flood concerns."
The greatest concerns stretch from the Mississippi Valley into the Ohio and Tennessee valleys, where repeated rounds of storms will likely bring significant rainfall totals with local amounts up to a foot by the weekend, the FOX Forecast Center said. As much as 3-5 inches of rain could fall on Thursday alone, leading to early flash flood concerns.
Due to this, the highest level of flash flood risk has been issued for Thursday in parts of western Kentucky, the Bootheel of Missouri, West Tennessee and northeastern Arkansas.
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The FOX Forecast Center said concerns are that storms will move over the same area over and over, a process called "training." Computer forecast models have been indicating several-inch rainfall totals, especially across Arkansas into western Kentucky, where 24-hour totals in excess of 5-8 inches are possible in some spots. This is on top of several inches of rain that will have already fallen in previous days.
"This is an increasingly significant setup approaching with potential for high impacts and life-threatening flash flooding spanning the course of several days," the WPC said. "Be sure to prepare if you live in a flood zone anywhere from Arkansas, northeast through the Ohio/Tennessee valleys."
The unsettled pattern will continue into Friday and Saturday, with heavy rain and severe storms potentially persisting. By the weekend, rainfall totals could approach or exceed a foot.
The National Weather Service in Paducah, Kentucky, where a state of emergency has been issued, said storm total rainfall now ranges from 8-12 inches over the Quad State, with the highest amounts straddling the Ohio River and the lowest amounts in the far northwest and the far southeast.
"If we get anywhere near these amounts, a historic flash flooding event is likely over a large portion of the Quad State," the agency warned. "Widespread river flooding will likely develop as well."
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