CNN — (CNN) -- "Turn around ... don't drown."
With those words, the National Weather Service warned motorists in and around Lansing and Hastings, Michigan, not to drive through flooded streets early Thursday.
The weather service assured motorists they would see such flooding in the wake of a storm system that wracked the upper Midwest on Wednesday with hail, strong winds and at least one confirmed tornado.
More warnings were issued from West Virginia to Massachusetts as the system moved east Thursday.
Clouds stalling out over Michigan were likely to result in "excessive rainfall" that would "cause flash flooding to occur," the weather service said overnight.
"Do not underestimate the power of flood waters," it warned in a flash flood bulletin. "Only a few inches of rapidly flowing water can quickly carry away your vehicle."
Residents of Fort Wayne, Indiana, received a similar warning. "Flooding is occurring or is imminent," the service said.
A system of straight-line winds that slammed Chicago with 50 mph gusts and golf-ball-size hail Wednesday reportedly bowled over trees and some buildings in Auglaize, Ohio, early Thursday, said CNN meteorologist Ivan Cabrera.
Local media in the state reported hundreds of households had lost electricity.
The "derecho," as the windy system is called, usually builds in the Midwest then heads east, he said. "Derecho" is a Spanish word that means straight.
The system resembles a squall line, but instead of potentially producing tornadoes, it sends out a slicing wind.
Derechos usually dissipate quickly, but "this one is holding together pretty good," Cabrera said. It could make it to the East Coast.
Behind it is a band of thunderstorms throwing down lots of lightning and heavy rain.
A broad swath of flood warnings and watches extends from Illinois to the Atlantic.
Federal Emergency Management Agency officials said Thursday that officials have been in touch with its state and local emergency management counterparts and with the National Weather Service as it monitors the system.