(CNN) — Residents across a swath of the central United States braced Thursday evening for tornadoes tied to a system that has already brought drenching rains to the region.
The National Weather Service said the greatest risk lies in the middle and lower Mississippi River Valley, the Ozarks and the western Tennessee and Ohio valleys.
The National Weather Service’s Storm Prediction Center said on its website that a “confirmed tornado” was spotted Thursday in the Osage County community of Rich Fountain, Missouri.
The same agency reported a “damaging” tornado about 60 miles east — and some 50 miles west of St. Louis — near Washington, at about 7:11 p.m. (8:11 p.m. ET). This twister was “moving east at 35 mph” and accompanied by quarter-size hail, according to the weather service.
It was not immediately clear whether there was any related injuries or damage in either of these Missouri locales.
Denton County, Texas, sheriff’s office spokeswoman Sandi Brackeen said that “a tornado touched down south of Krum,” though the weather service hasn’t confirmed a tornado in this area. Outbuildings and barns, but no known homes or commercial properties, suffered damage, said county emergency services chief Jody Gonzalez.
“We do have significant hail damage across the county — downed tree limbs, roof and gutter damage, and busted windows,” Gonzalez said, adding that some residents “took pictures of little rope tornadoes that did touch down.”
“We do not have any reports of injuries,” Gonzalez said.
While the threat of tornadoes often dies down when the sun and temperatures go down, that won’t necessarily be the case Thursday. CNN meteorologist Chad Myers noted twisters could pop up “through midnight or later.”
“The tornado risk is actually increasing,” veteran storm chaser Jeff Piotrowski told CNN around 5:45 p.m. (6:45 p.m. ET) in southwest Missouri, predicting “things are going to change rapidly over the next hour or two.”
St. Louis awoke to tornado sirens Thursday as the cluster of heavy thunderstorms began sweeping through the central United States.
The weather service confirmed a tornado touched down about an hour before sunrise in the St. Louis suburb of University City, gouging a half-mile-by-100-yard path. The weather service gave the tornado an initial rating of EF-1, packing top winds of 112 miles per hour.
The twister knocked down trees and ripped up a gas main in University City, but there were no injuries, University City Mayor Shelley Welsch reported via Twitter. St. Louis County officials said about 100 homes had been damaged.
It wasn’t just strong winds that were a problem.
The national Storm Prediction Center noted reports of large hail falling Thursday in parts of Missouri, Arkansas, Kansas, Oklahoma and Texas. Renato Reyes-Gomez sent CNNiReport a picture of golf-ball-size hail in Denton, Texas, saying he cannot recall anything “ever this big.”
Authorities in Jefferson County, Missouri, made “a couple of water rescues and evacuated a couple of mobile homes” due to rising waters there tied to flash-flooding reports that first came in around 2:15 p.m, said the county emergency management spokesman Warren Robinson.
While several highways had closed, Robinson didn’t know of any significant damage in his eastern Missouri county.
In addition to nearby St. Louis, cities from Houston to Indianapolis faced a high risk of tornadoes through Thursday night, while some parts of the Midwest could see up to 5 inches of rain, the weather service reported.
Thursday is the 40th anniversary of the “super tornado” outbreak of 1974, when 148 twisters killed 330 people across 13 states.