ATLANTA -- At least six people were killed as a storm system barreled across the South on Tuesday and lashed states along the East Coast on Wednesday, the authorities said.
The system, which spawned tornadoes and heavy rains, flattened homes, tossed vehicles and uprooted trees.
The Virginia State Police said Wednesday that three people had been killed in Waverly, where a suspected tornado left roads impassable and at least five structures damaged.
Those deaths, on Wednesday afternoon, came after three fatalities on Tuesday in the Deep South.
The National Weather Service said the severe conditions could last into Wednesday evening and that millions of people were at some risk.
On Wednesday afternoon, the federal forecasters said that Raleigh, North Carolina, and Richmond, Virginia, were at "moderate" risk of severe weather, and that Baltimore, Philadelphia and Washington faced an "enhanced" risk.
"A powerful weather disturbance will move across the Eastern United States today," Ariel Cohen, a Weather Service forecaster, said on Wednesday in a briefing.
"Strong winds throughout the atmosphere in association with this system will support rotating thunderstorms capable of producing tornadoes." Ahead of Wednesday's outbreak, the authorities urged residents to prepare for storms, and Gov. Pat McCrory of North Carolina said that he had placed 14 rescue teams on standby.
In North Carolina and elsewhere, dozens of school systems closed early, and many businesses and government agencies sent workers home.
Since Tuesday morning, forecasters have issued tornado warnings in Alabama, Florida, Georgia, Louisiana, Maryland, Mississippi, North Carolina, Pennsylvania, South Carolina, Texas and Virginia. Tens of thousands of customers at least briefly lost electricity.
In St. James Parish, Louisiana, where a suspected tornado on Tuesday damaged about 100 homes at the Sugar Hill RV Park, the Sheriff's Office reported two fatalities. An ambulance service said it had transported more than 30 people.
"We will do all that we can to help restore the families, business and communities destroyed by this tragedy," said Gov. John Bel Edwards of Louisiana, who toured storm damage Tuesday night in Convent and declared emergencies in nine parishes.
The Mississippi authorities said there had been one death in the state.
Officials in Escambia County, Florida, said six people were injured and at least two dozen apartments were destroyed.
More than 20 miles of Interstate 10 was closed for part of Tuesday night but had reopened by Wednesday.