A severe storm swept through North Texas on Tuesday, knocking out power to thousands of customers, damaging buildings and prompting school closures and evacuations, the authorities said. More than 350,000 customers in Texas were without power on Tuesday afternoon, with the majority in North Texas, as the storm's strong winds swept across the region. Nearly a dozen counties in the Dallas-Fort Worth area were affected. It was not clear how many power outages were directly caused by the storm. The storm, part of what forecasters have called an "unusually strong" storm system that stretched from Iowa to Texas, was expected to strengthen as it moved east, bringing damaging winds, blizzard conditions and chances of localized flash flooding, according to the National Weather Service. Warnings were in place for blizzards in the Great Plains and severe storms across the South, with damaging gusts, hail and possible tornadoes forecast from eastern Oklahoma to Alabama and in western parts of Florida. The system was expected to affect much of the East Coast on Wednesday. In Irving, just northwest of Dallas, most of the damage was felt in an area of about 2 square miles in the southern section of the city of about 250,000 people. Meteorologists with the weather service were investigating whether it was a tornado that had carved the destructive path, Officer Anthony Alexander, a spokesperson for the Irving Police Department, said Tuesday. A roof was ripped from a two-floor apartment building, prompting the evacuation of about 340 people, he said. "These winds took the roof right off the structure," he said. Another apartment building's roof was partially torn off, leading to almost two dozen residents seeking shelter elsewhere. Two schools were closed in the same area, although elsewhere in the city, schools remained open as power was restored to them. The storm "hit the middle of the city on the southern side," Alexander said. "There are pockets here and there with downed power lines and trees." Shelters were opened at the Georgia Farrow Recreation Center in Irving. There were no reported injuries, he said. In Plano, Texas, roughly 30 miles from Irving, the storm ripped part of the roof off a high school, according to WFAA, a television station in Dallas. The storm also caused travel disruptions, with nearly 500 flights canceled at Dallas-Fort Worth International Airport on Tuesday, and hundreds more delayed, according to FlightAware, a website that tracks flight data. A wind advisory was in effect for north and central Texas through 9 p.m., with sustained winds and gusts of up to 50 mph expected, according to the weather service. The combination of strong winds and low humidity had increased the risk of wildfires, the weather service said, urging people to avoid any activity that could start a fire. The weather service had forecast possible tornadoes, damaging winds, large hail and heavy rain in the early part of the week. On Monday, Gov. Greg Abbott directed emergency resources to be put into place as the state braced for the storms and wildfire risk. In southern Oklahoma, about 15,000 customers were without power as of Tuesday afternoon, according to poweroutage.us. A mobile home in Ada, Oklahoma, was destroyed after a possible tornado, according to KOCO-TV, a television station in Oklahoma City. This article originally appeared in The New York Times.