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Multiple extremely strong tornadoes will most likely tear through parts of the central United States on Wednesday ahead of days of potentially once-in-a-lifetime flooding hitting the same region of the Midwest and South, forecasters said.
National Weather Service offices warned of the potential for a “tornado outbreak” across a region that stretches from Texas to Michigan, with special risk alerts in place for the Memphis area, home to 1.3 million people. The storm system generating these tornadoes is expected to stall by Thursday, prompting the government forecasters to issue their highest alert for flooding over this same area as more than a foot of rain may fall over the next five days.
Forecasters issued a “particularly dangerous situation” tornado watch for portions of seven states: Arkansas, Tennessee, Illinois, Indiana, Missouri, Kentucky and Mississippi.
The strong language of the “particularly dangerous situation” designation is used by the Weather Service when forecasters want to grab attention; it only gets used in rare events, mainly when strong and violent tornadoes are possible but also in other extremely critical events such as wildfires and floods.
Intense storms in this area this afternoon and evening are expected over a relatively broad regional area, with multiple rounds of severe storms possible in some areas. The governors of Kentucky and Arkansas pre-emptively declared states of emergency on Wednesday.
Meteorologists said the system would not move quickly, allowing heavy rains to persist from Wednesday through the weekend. The relentless rain may lead to “significant and potentially historic” rainfall totals of 10 to 15 inches. This could create what forecasters called a “generational flooding” event, particularly in a region stretching from northeast Arkansas through western Tennessee, western Kentucky and into southern Indiana.
“One of the problems is that this storm system isn’t going to be allowed to continue moving east,” said Richard Bann, a meteorologist with the Weather Prediction Center. An area of high pressure off the Atlantic coast will block it, he said, keeping the storm stalled while warm, moisture-laden air from the Gulf fuels heavy downpours. “That’s the crux of our concern,” Mr. Bann said.
The Weather Prediction Center has placed areas from northeast Arkansas through the mid-Mississippi Valley and into southern Indiana under a threat of “high risk,” what it calls a Level 4 out of 4, for excessive rainfall on Thursday.
A higher risk of excessive rainfall shouldn’t be taken lightly. Over the past decade, some of the deadliest and most destructive floods have occurred in areas that forecasters said were at this level of risk — a level they rarely use. Areas that don’t usually experience flooding might in this case.
This storm has been building for days.
This storm system originated on the West Coast on Monday, where it brought heavy snow to the Sierra Nevada mountain range, which straddles California and Nevada. By Tuesday it had moved into the Plains, triggering severe thunderstorms.
But its most widespread and severe threat is expected on Wednesday and Wednesday night, across a region stretching from Illinois, Indiana and Ohio to Arkansas, Louisiana and Texas.
The Storm Prediction Center has issued a high risk — a Level 5 out of 5 on its scale — for these areas, cautioning that “widespread” thunderstorms could produce destructive winds, large hail and significant long-track tornadoes.
These severe storms could be particularly intense, and long-lasting severe storms at this high of a level are typically experienced only once or twice in a lifetime. This higher level of risk means forecasters with experience predicting severe storms believe widespread storms are expected to occur near or at this location.
The most likely area for tornadoes is from Arkansas to Indiana, but the chance exists as far south as Texas and as far north as Michigan.
The pattern of spring storms has been relentless.
These storms follow a series of severe weather events that have battered the central and eastern United States in recent weeks. Most recently, over the weekend, a powerful system swept through many of the same states, bringing damaging winds, power outages and flooding. In Oklahoma, a tree fell onto a trailer, killing one person, and three children in Michigan were killed after a tree struck their vehicle on Sunday.
While severe spring storms are common, the excessive rainfall leading to potential widespread flooding is more unusual, Mr. Bann said.
“It’s not something that happens every year, particularly in places like the Ohio Valley, along the Ohio River, Illinois, Indiana and in parts of Ohio,” he said, “but we have had scenarios like this before.”
The storm is expected to begin moving east later in the week. “Things will finally start getting a real push during the latter part of the weekend,” Mr. Bann said.
You can track the risk with our weather maps here.
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