Blizzard conditions threaten Plains, Midwest and holiday travel A dozen states have been slammed with winter weather and another 12 may be affected in the days ahead as the icy blast that swept through the Rockies heads East. A major snowstorm sweeping across the Midwest brought blizzard warnings Thursday and threatened to dump more than a foot of snow on parts of the Central Plains. Travel will be "very difficult or impossible" in "a wide swath of the Plains and Upper Midwest," The Weather Channel reported, bringing the prospect of delays at O'Hare International Airport in Chicago, the nation's second-busiest. Snow warnings have also intensified, with more than a foot forecast for parts of Iowa by Thursday morning. Up to 4 inches is forecast at O'Hare airport, Weather Channel forecaster Brian Fortier told NBC News, including the possibility of a heavy snow shower there Thursday evening. Airlines were letting travelers flying to some Midwest cities change their bookings without fees. The storm has already delivered heavy snow and strong winds to parts of the West, where trucks tangled on icy roads on the Oregon and California state line. In West Texas, winds from the same system kicked up a dust storm that caused a series of accidents along Interstate 27, resulting in one death and more than a dozen injuries, NBC station KCBD of Lubbock reported. As snow blew sideways in Nebraska on Wednesday night, the Nebraska State Patrol closed parts of Interstate 80, a major east-west highway. Gov. Scott Walker declared a state of emergency in Wisconsin on Wednesday, where schools were canceled in advance of heavy snowfall and the University of Wisconsin-Madison postponed Thursday's final exams. Read full coverage of the storm at The Weather Channel The storm will bring with it "severe thunderstorms, damaging winds and fire weather conditions to the central United States," the National Weather Service warned. Meanwhile, another storm is beginning to affect the Pacific Northwest and Northern California, where heavy mountain snow and coastal flash flooding are possible through at least Thursday. In Chicago, people were making a run on snow shovels and salt ahead of what would be the first snow to hit the city in 290 days (the record is 296). The Home Depot in Lincoln Park sold 50 shovels by 1 p.m., NBCChicago.com reported. "It's Chicago, anything can happen," resident Louis Collazo said. I'm ready for it. Bring it on. The storm has package delivery companies nervously checking the weather forecast during this busy time of year. "We're closely monitoring the storm," FedEx spokesman Scott Fiedler told NBC News. We have a team of 15 meteorologists who track the weather around the world every day. Related in Travel: Winter storm threatens holiday travelers, gifts The storm intensified Wednesday night in Nebraska, Iowa, Wisconsin and northern Michigan, where 6 to 12 inches of snowfall was predicted, Fortier said. "Thunder snow" with lightning was reported in parts of Iowa. After blowing through the Midwest, the storm will move on to the East Coast in the form of wind and rain, according to The Weather Channel. The storm's warmer southern edge was expected to trigger thunderstorms overnight Wednesday, according to the Weather Channel, and the "chance of a few tornadoes cannot be ruled out." Isolde Raftery and A. Pawlowski, of NBC News, and Reuters contributed to this report.