A storm system sweeping over large areas of the U.S. South and Midwest resulted in at least 16 weather-related deaths by early Sunday, with overnight tornado and flash flood warnings setting up more severe weather that forecasters say could cause rising waterways for days to come.

Tornadoes and violent winds flattened homes and ripped apart buildings from Oklahoma to Indiana in the first round of storms that are expected to bring record-setting rains and life-threatening flash floods across the nation's midsection in the coming days.

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. Forecasters warned that rivers in some places would continue to rise for days.