Severe Storms in the Midwest Could Bring Tornadoes to Over a Dozen States

Widespread and potentially severe thunderstorms, including the possibility of damaging winds and tornadoes, are likely on Friday for over a dozen states in the Midwest and the mid-South, potentially affecting over 30 million people.

The thunderstorms, which could bring heavy rain and flash flooding threats, are likely to begin in the middle-to-lower Mississippi Valley and then quickly move through the Midwest, Ohio and Tennessee Valley throughout the night. Tornadoes, large hail and strong winds are possible, according to the National Weather Service’s latest forecast.

The risk area includes some of the areas devastated by tornadoes last week, like Mississippi, where at least 26 were killed.

“We’ve had a fairly high number of higher-end severe weather events” this year, said Bill Bunting, chief of forecast operations at the Storm Prediction Center. “Storm systems this year have been frequent. They’ve been intense. Qualitatively, I would say it’s a more active year than normal.”

Friday’s storm system will add to the active year and could affect an area stretching from Louisiana to Wisconsin, including Memphis, Nashville, St. Louis, Chicago and other major cities.

The reason the risk area is so large has to do with how fast-moving this storm system will be, Mr. Bunting said. It’s a strong system that will cover a lot of ground during the day on Friday and overnight into Saturday morning.

For severe storms occurring in the cold season, like this storm, there is typically not as much thunderstorm development as there is in late spring and early summer. “Like a lot of cool-season events that are strong and fascinating, it could be a pretty widespread severe weather event,” Mr. Bunting said. Not every part of the risk area will be affected by severe storms, but the conditions could allow more storms to form than would be the case at other times of year.

Further north, ice and snow will be a threat. More than a foot of snow could fall in parts of northeastern South Dakota, northeast Wisconsin and into large portions of the Upper Peninsula of Michigan. Ice accumulations of a quarter of an inch could also be possible throughout those regions, including central Minnesota. Strong winds, with gusts over 50 m.p.h., could create blizzard conditions and make travel difficult, forecasters said.

Mr. Bunting recommends that anyone living in the risk area take the rest of Thursday to prepare, create a plan and have a way of getting warnings on Friday.

With the likelihood that these storms will move very quickly, he urged people not to wait until the dangerous weather is clearly visible. The best plan of action, he said, includes heeding warnings issued by the National Weather Service and being prepared.

McKenna Oxendencontributed reporting.