A continuous line of powerful storms may create an unusual weather event called derecho – a massive system of straight-line winds spanning at least 240 miles.
The National Weather Service says 64 million people in 10 states are under a heightened risk of dangerous weather. A gigantic line of powerful thunderstorms could affect one in five Americans on Wednesday as it rumbles from Iowa to Maryland packing hail, lightning and tree-toppling winds.
National Weather Service officials say two tornadoes touched down in northern Iowa. They say a tornado touched down about 5 p.m. Wednesday and was moving east at 25 mph toward the town of Hampton in Franklin County. The first tornado was reported about 4:30 p.m. near Belmond in nearby Wright County and was moving east at 30 mph. Some debris was reported for the first tornado, but additional information about damage or injuries for both tornadoes is not available
National Weather Service authorities are reporting several small tornados, quarter-sized hail and winds of up to 60 mph as severe weather moves across northern Illinois. Severe storms were hitting the Rockford area and moving to the east. Meanwhile, airlines canceled more than 120 flights at Chicago's O'Hare International Airport. And Wednesday night's White Sox game was postponed.
Northern Indiana's largest utility says it has increased staffing to cope with any outages caused by a massive line of thunderstorms bearing down on Indiana. The storms are expected to push into northwest Indiana early Wednesday evening. The Northern Indiana Public Service Co. says it is increasing staff at its customer call center and scheduling extra work crews to handle any outages.
The National Weather Service in Grand Rapids has issued a severe thunderstorm and flash flood watches for parts of southwest Michigan and counties near the Indiana state line. Officials say 1 to 3 inches of rain could be dumped on parts of southwest Michigan within a couple of hours.
A storm dumped heavy rain to parts of southern Minnesota Wednesday morning, including nearly 3.25 inches at Hutchinson airfield, 3.3 inches in Arlington, 2.83 inches in Carver and 2.28 inches near Green Isle. Madison, in far western Minnesota, recorded a wind gust of 65 mph. No significant damage was reported. A tornado watch remained in effect for Fillmore, Houston and Mower counties in southeastern Minnesota until 9 p.m.
The entire state of Pennsylvania remains under a flood watch for high waters overnight and through the day Thursday. National Weather Service officials say the greatest risk of flooding is in the northern portion of the state, while the worst thunderstorms are expected in southern areas. Parks events Wednesday night and a downtown farmers' market on Thursday were among events canceled. Public safety and public works personnel are being added and some equipment is being repositioned to prepare for possible flooding or downed trees and wires.
Last year, a derecho caused at least $1 billion in damage from Chicago to Washington, killing 13 people and leaving more than four million people without power. Another 34 people died from the heat wave that followed in areas without power.
The storms are the type that will move so fast that "by the time you see the dark sky and distant thunder you may have only minutes to get to safe shelter,"according to Bill Bunting, operations chief at the Storm Prediction Center.
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The Associated Press contributed to this report