Volatile spring weather will kick into high gear this week as a potential severe thunderstorm outbreak and life-threatening flooding loom large for tens of millions of people in the central and eastern United States.

Widespread storms are expected to sweep through a region stretching from Texas to Michigan on Sunday. Some of the most severe weather is expected in the Ohio and Tennessee River Valleys, where forecasters said the conditions are right for “very large hail, damaging winds and strong tornadoes.”