A powerful low-pressure system is likely to spawn a dangerous outbreak of severe thunderstorms in portions of the Midwest, South and East, where tornadoes, widespread damaging winds, large hail and flash flooding are all concerns.

The threat of tornadoes moved east into the Mississippi Valley and Deep South on Saturday, a day after a massive storm system moving across the country unleashed winds that damaged buildings, whipped up dust storms that caused deadly crashes and fanned more than 100 wildfires in several central states.