Massive, days-long winter storm starts hitting large swaths of U.S.

States in the northern plains were largely shutting down ahead of a massive winter storm that could dump up to 2 feet of snow in some areas, accompanied by strong winds and dangerously cold temperatures. The system stretches as far west as California.

More than 75 million americans are under winter weather alerts in 29 states, CBS News weather producer David Parkinson says.

Many schools throughout the Dakotas, Minnesota and Wisconsin were called off for Wednesday, ahead of the storm. Offices closed, and so did the Minnesota Legislature, which won't reconvene until Monday. Emergency management leaders warned people to stay off the roads or face potential "whiteout" conditions due to the snow and fierce winds.