Large portions of the Midwest and the Mid-Atlantic are at significant risk of severe weather on Friday, as a multiday storm system moves slowly to the East. A bull’s-eye centered over parts of Missouri, Illinois, and Indiana and Kentucky is at risk for some of the most severe weather.

These storms will be capable of unleashing large hail, damaging winds and tornadoes, possibly some strong ones.

“I’d be surprised if we didn’t see some tornadoes in that corridor,” said Aaron Gleason, a meteorologist with the Storm Prediction Center.

The risk on Friday generally stretches from eastern Texas into the Mid-Atlantic and the Northeast.

By early afternoon, an area of the East Coast that includes southern New Jersey, Central Pennsylvania, Philadelphia and Delaware had been under a rolling series of flash flood and tornado warnings.

Across parts of the middle Mississippi Valley and the Ohio Valley, the potential for severe weather will be greatest in the afternoon and the evening, with the storms expected to persist overnight.

On Thursday, at least 11 tornadoes spun up across the Upper Midwest, including one that was reported in Mayville, Wis., that damaged businesses and homes, forcing road closures and downing power lines, the authorities said. More than 300,000 customers in the region are still without power.

“It’s a fairly broad area for severe potential, and it looks like all hazards could be possible,” Mr. Gleason said.

The area of highest concerns includes Bloomington, Ind.; Evansville, Ind.; Louisville, Ky.; and St. Louis.

Those areas are at particular risk of supercells, highly organized, longer-lasting storms that produce even stronger winds and larger hail — in the case of Friday, bigger than baseballs — than typical thunderstorms.

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