A deadly tornado outbreak ripped through the South and Midwest Wednesday and Thursday, destroying homes and neighborhoods, damaging vehicles, bringing down trees and utility lines and knocking out power.

The National Weather Service described the disaster as "a once-in-a-generation to once-in-a-lifetime" event, warning that the worst may still be ahead.

Tornadoes and violent storms struck parts of the South and Midwest on Wednesday, knocking down power lines and trees, ripping roofs off homes, shooting debris thousands of feet into the air, and killing at least one person in southeast Missouri.

A storm system sweeping over large areas of the U.S. South and Midwest has resulted in at least 16 weather-related deaths, with overnight tornado and flash flood warnings setting up more severe weather.

Another round of torrential rain and flash flooding came Saturday for parts of the South and Midwest already heavily waterlogged by days of severe storms that also spawned deadly tornadoes.

Rivers rose and flooding worsened across the U.S. South and Midwest, threatening communities already waterlogged and badly damaged by days of heavy rain and wind that killed at least 18

About 22 million people are at risk for severe storms Sunday, stretching from central North Carolina southwestward to the central Gulf Coast, according to the Storm Prediction Center.

Torrential rains and flash flooding battered parts of the Midwest and South on Friday, killing a boy in Kentucky who was swept away as he walked to catch his school bus. Many communities were left reeling from tornadoes that destroyed entire neighborhoods and killed at least seven people earlier this week.

The storm inundating a large stretch of the South and Midwest has wreaked havoc since Wednesday. But heavy rain and flooding are likely to ease considerably by Monday.