Much of the eastern U.S. and Midwest was facing the threat of severe thunderstorms and heavy rainfall, while heat alerts were issued Sunday for over 50 million people from Kansas to the Carolinas. The big picture: NOAA's Weather Prediction Center issued a Level 3 out of 4 risk for excessive rainfall over parts of the Ohio Valley through Monday morning,

Slow-moving storms could bring up to 11 inches of rain, raising the risk of flash floods on Sunday, particularly in Illinois and Indiana, forecasters said.