12 / 30

This photo provided by the Iowa State Patrol shows the scene of a 25-vehicle pileup that killed three people Thursday, Dec. 20, 2012 north of Des Moines, Iowa. Authorities said drivers were blinded by blowing snow and didn’t see vehicles that had slowed or stopped on Interstate 80 about 60 miles north of Des Moines. A chain reaction of crashes involving semitrailers and passenger cars closed down a section of the highway. (AP Photo/Iowa State Patrol)

This photo provided by the Iowa State Patrol shows the scene of a 25-vehicle pileup that killed three people Thursday, Dec. 20, 2012 north of Des Moines, Iowa. Authorities said drivers were blinded by blowing snow and didn’t see vehicles that had slowed or stopped on Interstate 80 about 60 miles north of Des Moines. A chain reaction of crashes involving semitrailers and passenger cars closed down a section of the highway. (AP Photo/Iowa State Patrol)

Winter storms hit U.S.

A winter storm system that blew

through Christmas Day with Gulf Coast tornadoes and snow in the nation's

midsection headed for the Northeast, spreading blizzard conditions that slowed holiday travel all week. The death toll rose to six with car accidents on snow and highways.