Severe Storms Threaten 90 Million Across US Midwest

The volatile pattern is being driven by a deep dip in the jet stream pushing across the West Coast and a surface low advancing northward, which together feed instability into the central states. High dew points and strong daytime heating are providing the moisture and energy needed to fuel supercells and bowed storm lines. Earlier rounds of severe weather had already drenched the South and Northeast: parts of Tennessee received as much as 9 inches of rain, a flash-flood emergency was declared near Huntsville, Alabama, and the National Oceanic and Atmospheric Administration's (NOAA) Storm Prediction Center is warning of a "potentially significant severe weather event" for the Upper Midwest mid-week.

The storms have already proved deadly. In New York City, an 85-year-old man was killed by a falling tree in Queens during weekend wind gusts that reached 64 miles per hour in Brooklyn and downed more than 250 trees across the city. In Pittsburgh, resident Tim Broadwater told CBS Mornings his home was knocked off its cement supports by violent gusts. Flood watches affecting about 6 million people remain in effect across parts of the Midwest, and forecasters expect the threat to extend through Thursday, when more than 26 million Americans in metropolitan areas such as Chicago, St. Louis, and Milwaukee will face renewed risk of hail, tornadoes, and flooding as the cold front marches east.