By Brendan O'Brien
MILWAUKEE (Reuters) - A large swath of the U.S. Midwest is bracing for potentially dangerous weather including possible tornadoes as an intense storm system moves through the region on Wednesday and Thursday, according to the National Weather Service.
The area of greatest risk includes Oklahoma, Arkansas, southern Missouri and Illinois and western Kentucky and Tennessee, where significant tornadoes, large hail and damaging winds could strike Thursday afternoon and evening, said John Hart, a meteorologist in the service's storm prediction center.
"The parameters look pretty good for tornadic storms tomorrow, but the models are varying quite a bit on where the corridor of greatest risk will be," Hart said.
The potential threat is caused by a strong weather system coming out of southwest along with moist, unstable air rising from the Gulf of Mexico, Hart said.
Thunderstorms expected to roll through the region on Wednesday and early Thursday, ahead of the more severe weather, could give forecasters a better sense of where the biggest potential will be for tornadoes, according to Hart.
"At this point, we just can't quite tell" where the threat of twisters is greatest, he said.
The upper Midwest also faces severe weather from Wednesday night through Friday as the forecast there includes freezing rain, sleet and snow, according to the weather service.
Last year's tornado season was historic for the region. On May 20, a top-of-scale EF5 twister with winds up to 200 mph, killed 24 people in Moore, Oklahoma. Two weeks later, another EF5 tornado measuring 2.6 miles wide, the widest ever measured in the United States, touched down near El Reno, Oklahoma.
(Editing by Scott Malone and Leslie Adler)