A flash flood emergency has been issued for the Midwest and South as forecasters warn of a 'historic' deluge - with up to 21 inches of rain expected in some areas

The National Weather Service warned on Thursday of "generational" floods in the southern and Midwestern United States, as storms ripped across a swath of the country from Texas to Michigan, flinging down hail and whipping up tornadoes.

At least two people were killed in Tennessee, officials said, and millions were under severe weather advisories. Flooding was reported in Nashville.

Two people were killed in Tennessee, officials said, and millions of people were under severe weather advisories and more than 300,000 customers had lost power.

A wide-reaching storm spawned several intense and violent tornadoes Wednesday and threatens near-nonstop rainfall Thursday that could trigger once-in-a-lifetime flooding. Follow here for live updates.

The potent storm system will bring “significant, life-threatening flash flooding” each day through Saturday, the National Weather Service said.

The National Weather Service warned on Thursday of "generational" floods in the U.S. South and Midwest as storms ripped across a swath of the country from Texas to Michigan, whipping up tornadoes and killing two people.

V iolent storms cut through a wide swath of the South and Midwest, spawning tornadoes and killing at least three people, knocking down power lines and trees and ripping roofs off homes. Dozens of tornado and severe thunderstorm warnings were issued Wednesday in parts of Arkansas,

Days of severe weather are likely from Texas to the Ohio Valley as thunderstorms begin to run over the same areas repeatedly. Tornadoes, large hail and damaging winds are all concerns in addition to flooding rainfall.