December 17–22, 2012 North American blizzard  The December 17–22, 2012 North American blizzard was a winter storm that affected the Midwestern and Eastern United States. Forming on December 17, the winter storm moved across the midwest, forcing schools to close throughout the region. Numerous warnings and advisories had been posted by the National Weather Service for many states, including Iowa, Nebraska, Illinois, and Wisconsin. Both O'Hare International Airport and Midway International Airport in Chicago, Illinois canceled most departures and arrivals. According to flight tracking website FlightStats.com, more than 1,000 flights were canceled across the region. More than 130,000 customers were without power across the west and midwest. In addition to snow, strong thunderstorms and possible tornadoes went across the Southern United States. A multiple-car pileup on Interstate 35 in Fort Dodge, Iowa killed two people, according to the Iowa State Patrol. American Airlines, American Eagle Airlines, and Southwest Airlines collectively canceled a total of 573 flights in the midwest. Greyhound Lines also canceled service in Chicago, Minneapolis, and Indianapolis. The storm moved east towards the Northeast and New England. Winter storm and blizzard warnings were issued from north New York to western Pennsylvania. On December 17, an upper-level shortwave and associated trough made landfall along the coast of the Pacific Northwest. The system initially moved towards the southeast, strengthening over the Rocky Mountains. This led to the development and formation of a surface low over eastern Colorado early on December 19. The low began to curve towards the northeast, and its barometric pressure began to deepen. The low attained its lowest pressure at 1800 UTC on December 20 over northern Illinois. However, the system became occluded, and as such moved quickly to the northeast, where it weakened and subsequently dissipated over southern Ontario late on December 21. Another low pressure area formed in the vicinity of the previous low over the East Coast of the United States, which quickly moved north across the coast, bringing heavy snowfalls to the region. The low later exited the continental United States on December 22. During the next several days, the winter storm drifted northeastward, and eventually to the south of Greenland, before finally being absorbed by another more powerful extratropical cyclone just south of Iceland, on December 29. A dry line associated with the system moved east across eastern Oklahoma and northwestern Arkansas, helping to trigger thunderstorm and shower development across Arkansas. The thunderstorms produced wind gusts as high as , downing trees and power lines.