Derecho odds fade as large storm system approaches Mid-Atlantic Updated at 11:49 a.m. WASHINGTON A massive storm system surged Thursday toward the Mid-Atlantic after causing widespread power outages but largely failing to live up to its billing in ferocity through the Upper Midwest. The Washington, D.C., area braced for the storms, and the National Weather Service issued severe thunderstorm watches and warnings for much of the region. Forecasters warned that the storms could produce damaging winds and large hail, and a flash flood watch was in effect. In Maryland and Delaware, officials reported trees down, roads closed, and tens of thousands of power outages after a line of heavy thunderstorms moved through. Storms with swift, straight-line winds also soaked parts of Ohio, damaging trees and barns and leaving many without power early Thursday as commuters dodged fallen branches on roads and faced backups at intersections where traffic lights were out. Straight-line winds topping 70 mph were reported and more than two dozen tornado warnings were issued as two rounds of storms pummeled the state, but no twisters have been confirmed, said Phillip Johnson, who was part of the team monitoring developments for the Ohio Emergency Management Agency. Play was suspended at the U.S. Open at Merion Golf Club outside Philadelphia less than two hours after the start of the first round. Ian Poulter held the lead with three birdies in three holes as fans scurried toward the merchandize tents to wait out the storm. A flash flood watch for the entire state of Pennsylvania was issued through Thursday night. Rush-hour commuters tried to get to work in the morning amid torrential downpours and dark skies that made it look like nighttime. In New Jersey, officials opened the soaked state's Emergency Operations Center on Thursday morning to monitor the storm's progress. The National Weather Service issued a flood watch for most of the state. Forecasters predicted 1 to 2 inches of rain will fall on swollen rivers and streams. As thunderstorms rumbled across the southern and central parts of the state, thousands of residents were left without power. Overnight, thunderstorms that punched through northern Illinois caused significant wind damage, mainly in rural areas west and south of Chicago. The weather service said intense winds estimated to have reached 70-80 mph in some areas snapped large trees at their trunks or uprooted them entirely. Barns were destroyed in northern Kankakee County. By early Thursday, the derecho that had been forecast hadn't developed. "With each hour that goes by, it's less likely," said Greg Carbin of the National Weather Service's Storm Prediction Center in Norman, Okla. A derecho is a storm of strong straight-line winds spanning at least 240 miles. The systems are distinctive and take on a comma or bow shape, and usually have a large area of very cold cloud tops not typically seen in an ordinary thunderstorm, said Ken Pryor, a research meteorologist at the Center for Satellite Applications and Research at the National Oceanic and Atmospheric Administration in College Park, Md. While the Midwest dodged a derecho, several tornadoes, large hail and flooding did some damage Wednesday. In the small town of Belmond, Iowa, about 90 miles north of Des Moines, Duwayne Abel, owner of Cattleman's Steaks & Provisions restaurant, said a tornado demolished part of the building. No one was in the restaurant at the time. "I was, oh, eight miles west of town and I looked toward town and I could see a funnel cloud, having no idea it was exactly where our restaurant was," Abel said. His wife and an employee were able to get out of the restaurant and sought shelter in a basement. In Iowa, at least two businesses and a home were damaged, authorities said. A storm ripped through a farm in rural Alexander, destroying a motor home. Tens of thousands of people across the Upper Midwest lost power. In Wisconsin, authorities said thunderstorms packing heavy rain and high winds caused a Wal-Mart roof to partially collapse. Lake Delton Fire Chief Darren Jorgenson says two employees had minor injuries, but no customers were hurt. "We're just happy that we don't have reports of injuries or fatalities," said Stephanie Bond with Iowa Homeland Security and Emergency Management. We just hope the extent of the damage is minimal. Winds reached nearly 100 mph in some places. In addition to the people killed in the storm, 34 more died from the heat wave that followed in areas without power. For Washington, Philadelphia and parts of the Mid-Atlantic, the big storm risk continues and even increases a bit Thursday, according to the weather service. In Washington, the Office of Personnel Management said federal agencies in the area would open but that workers would be allowed to take unscheduled leave or work from home.