David Duprey / AP
A tow truck operator attaches a cable to a car that crashed into a flooded ditch during heavy rain along the New York State Thruway in Buffalo, N.Y., on Thursday, June 13. The National Weather Service issued a flood watch for much of upstate New York, saying the region was in for two days of rain starting Thursday.
A tornado in Maryland as well as lightning, hail and heavy rain delayed flights and snarled work commutes along the East Coast on Thursday, caused by a massive storm system that tormented the Midwest a day earlier.
The storm turned deadly in Virginia, where a large, mature tree uprooted by the storm fell on a school-age child, killing him, police said. A man was also injured in the incident that took place at Maymont Park in Richmond, but his injuries are not life-threatening.
Flood warnings were in issued for New York, New Jersey, Connecticut and Washington, while severe thunderstorm warnings were also issued in the South and Southeast.
The National Weather Service confirmed a tornado near the Washington suburb of Laurel, Md., just after 4 p.m. ET Thursday, and said the twister was moving east at 50 mph. A tornado threat had been issued earlier in the day, extending all the way from southern New Jersey and southern Pennsylvania to the Gulf Coast, said Weather Channel forecaster Greg Forbes. The threat was highest from north and east Virginia to east Pennsylvania and central New Jersey.
In Maryland and Virginia, tornado watches expired at 4:30 p.m. ET.
Roughly 62 million Americans were in the path of severe weather, MSNBC Meteorologist Bill Karins said. Washington, D.C., Baltimore, Richmond, Va., and Philadelphia were expected to get the worst of it.
An initial batch of storms passed through the nation's capital Thursday morning, with more severe weather hitting the area in the evening, NBCWashington.com reported. Downed wires and trees were reported in nearby Frederick County, Md.; Baltimore-Washington International Thurgood Marshall Airport and Ronald Reagan National Airport ordered groundstops Thursday morning.
The storms delayed hundreds of people on planes and trains and created massive backups on area roadways. More than 360 flights were canceled at O'Hare International Airport. For a time, all inbound flights to O'Hare were kept at their origin. Midway International, to the south, saw another 50 cancellations.
Weather Service ground crews surveying damage on Thursday made preliminary confirmation of a derecho -- straight-line windstorms whose gusts can reach hurricane force -- happening Wednesday night into early Thursday morning in northern Indiana and northwest Ohio, The Weather Channel reported.
Winds during the likely derecho event, which completely destroyed a grain silo and two barns in the Wabash, Ind., area, were estimated at 90-100 mph in a swath 7 miles long and 3 miles wide.
The storm's broad path along the Eastern United States knocked out electricity for up to 200,000 people across several states. In Georgia alone, more than 162,000 customers were without power, officials said.
At least 55,000 customers were without power in Illinois and northwest Indiana after the storm system pushed through the Upper Midwest Wednesday, bringing suspected tornadoes to Chicago and Ohio. The Weather Service confirmed Thursday that the tornado that hit the Savanna area of Illinois, knocking a house off its foundation and damaging several smaller buildings, was an EF-2 storm with maximum winds of 135 mph.
New York and surrounding suburbs, already saturated with up to 7 inches of rain from the downpours Friday and Monday, primarily faced the threat of more flooding, NBCNewYork reported.
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A powerful supercell system pushed through metropolitan Cleveland in the early hours of Thursday, which forecasters earlier predicted would bring baseball-sized hailstones and more high winds.
It was the end of what Weather Channel meteorologist Mike Seidel had earlier warned was going to be a "long and ugly night" for Chicago, Detroit, Cleveland, Indianapolis and the rest of the Midwest.
Scott Eisen / AP
Lightning flashes over Chicago's skyline on Wednesday.
Kevin Gold / NOAA, file
This photo taken in LaPorte, Indiana, on June 29, 2012, shows a shelf cloud on the leading edge of a derecho.
The Weather Channel reported "buildings destroyed" in Auglaize County as powerful winds blew through Ohio's northern Miami Valley early Thursday, though no details were immediately available. In the same county, a semi truck was toppled by high winds, NBC station WDTN TV in Dayton reported.
In Lake Delton, Wis., a "very, very strong downpour of rain" caused the roof over a loading dock to collapse at a Wal-Mart store late Wednesday afternoon, police said.
Police Sgt. William Hitchcock told NBC station WTMJ of Milwaukee that no serious injuries were reported, but the store is likely to be closed through Thursday.
NBC News' Jeff Black, Catherine Cetta, Justin Kirschner, Elizabeth Chuck and Sophia Rosenbaum contributed to this report.
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This story was originally published on Thu Jun 13, 2013 8:29 PM EDT