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Tornadoes, flooding hit southern Plains as storm threat shifts east

The zone from eastern Texas to southern Arkansas is most at risk Thursday

Debris partly obscures the sign for the Academy of Seminole in Seminole, Okla., on May 4 after the area experienced severe weather. (AP)
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Multiple significant tornadoes tore through parts of Oklahoma and adjacent north Texas late Wednesday, destroying structures while storm chasers jammed roadways. Hail as large as baseballs and torrential rain also accompanied the storms, which brought dozens of reports of flooding in eastern Oklahoma and northwest Arkansas. Scores of high-water rescues were necessary, and waterways were cresting at historic levels Thursday morning.

The rash of severe weather marked Day 1 of a three-day severe-weather episode as storms trek toward the Southeast and Mid-Atlantic.

A tornado and flood are coming your way: Take cover or move higher?

Wednesday’s tornadoes

The Weather Service received reports of eight twisters Wednesday. Particularly hard-hit was the town of Seminole, about 50 miles east-southeast of Oklahoma City. That’s where a confirmed tornado struck the town shortly before 7 p.m. An additional rotating thunderstorm with dual tornadic circulations affected the town less than two hours later. Several residents were trapped but were freed by first responders. Minor injuries were reported.

Seminole had also been hit by a tornado Monday, meaning that — if Wednesday’s second storm produced a tornado ― three tornadoes would have struck the same town in three days.

The first of Wednesday night’s tornadoes also moved toward Cromwell, Okla., to the northeast of Seminole, while taking on a “wedge” structure.

In Texas, meanwhile, tornadoes danced in the Red River Valley and southern Panhandle for much of the afternoon. A tornado swallowed wind turbines in Crowell, about 60 miles west of Wichita Falls.

The same storm appears to have produced a larger, powerful tornado that took a left turn into the town of Lockett, Tex., after nightfall. The 90-degree left turn spared homes in Vernon, Tex., but spelled the demise of several structures in Lockett.

The tornado hit a storm chaser tour van carrying multiple passengers, but no serious injuries were reported.

Social media photos showed swarms of chase vehicles in pursuit of Wednesday’s twisters, some directly in their path, and generated debate on Twitter about whether chasers were taking unnecessary risks.

Flooding Wednesday night into Thursday morning

The storms, some of which tracked over the same areas repeatedly, also brought significant flash flooding in northeast Oklahoma, southeast Kansas, southwest Missouri and northwest Arkansas. A flash flood emergency, the most dire flood alert, was declared in Okmulgee County, Okla., before dawn Thursday. Okmulgee County is due south of Tulsa. Up to nine inches of rain fell in just a few hours.

In Muskogee, Okla., just to the east, first responders conducted about 50 high-water rescues, according to FOX Weather. Scores of water rescues were also reported in Fayetteville, Ark., where many roads were closed.

Water levels were still rising in the Illinois River basin in eastern Oklahoma on Thursday morning, creating a “life-threatening situation,” according to the National Weather Service Office in Tulsa. The water level at Eldon, about 65 miles east-southeast of Tulsa, was predicted to crest at a record high Thursday morning before rapidly receding.

Now the severe weather threat is continuing east. Thursday featured the chance of a few additional tornadoes as well as hail and flooding over the mid-Missouri Valley, and storms will rumble to the Southeast by Friday.

Thursday’s storm threat

  • Areas affected: On Thursday, a level 3 out of 5 “enhanced” risk of severe weather had been hoisted by the National Weather Service Storm Prediction Center and was drawn to include northeast Texas, northwest Louisiana and southern Arkansas. Within the risk bull’s eye are Waco, Tyler, Longview and Killeen, Tex., as well as Shreveport, La. A broader level 2 out of 5 slight risk stretches from roughly Austin to southwest of Bowling Green, Ky., and encompasses Memphis and Jackson, Tenn.
  • Summary: The leftovers of Wednesday’s storminess are manifesting as a broken squall line that will push toward the Mississippi River. The amount of fuel for storms in the atmosphere is considerably less, meaning the odds of widespread severe weather and violent storms are slimmer than on Wednesday.
  • Hazards: Sporadic 60 mph wind gusts may occur within the heavier elements of the line, along with quarter-size hail. An isolated tornado can’t be ruled out along the line. That said, the apparent severe-weather risk has decreased some since previous assessments.
  • Heavy rainfall: Heavy rainfall continued Thursday morning near the Interstate 40 corridor in eastern Oklahoma and the Ozarks, where flooding remained possible through midday. There is a slight risk of excessive rainfall and flooding farther east in Arkansas and Missouri through later in the day.

Friday’s threat

  • Areas affected: The risk area occupies much of the Southeast and the southern Mid-Atlantic on Friday. Mobile, Ala., Atlanta, Charlotte, Raleigh and Richmond are all in a level 2 out of 5 “slight” risk, indicating the potential for widely-scattered instances of severe weather.
  • Summary: Showers and thunderstorms will roll across the risk area in a broken line, with enough jet stream energy in the upper atmosphere that the heaviest storms could mix down stronger momentum from aloft. That would translate to locally damaging gusts. More concerning is the potential for an isolated rotating storm ahead of the main line in northern North Carolina or southern Virginia; any such “discrete” supercell would be capable of producing hail to the size of half-dollars, winds gusting to 70 mph or even a tornado. The Storm Prediction Center has highlighted a narrow region along the North Carolina-Virginia border to raise awareness of that threat.

Saturday onward

On Saturday, there’s a marginal risk of one or two severe thunderstorms somewhere across central or northern Nebraska or southwest South Dakota.

By Sunday, the forecast becomes considerably trickier. There will be a robust supply of thunderstorm fuel simmering in the lower atmosphere in eastern Oklahoma and Kansas, primarily along and east of Interstate 35. The question is whether a strong “cap” of warm air a mile or so above the ground will suppress that instability all day and prevent surface parcels of air from rising. That looks likely at this point. If a storm can develop, it would become severe, but that’s a highly conditional threat since the cap looks to squash storm chances.

A similar setup will be present over the Corn Belt and Upper Midwest on Monday and/or Tuesday, with a return to High Plains storminess likely thereafter. Anything beyond Sunday is riddled with bountiful uncertainty, however, precluding more-detailed forecasts.

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