Dozens of motorists are already stranded by a blizzard that's left thousands of power customers in the dark, and state officials say it's going to keep causing problems as it moves east.
A long stretch of Interstate 90, where dozens of vehicles are trapped, is already closed. Some motorists have been stranded for more than 24 hours, and South Dakota's governor says search teams can't get to them because of zero visibility.
There have been more than 400 calls for assistance, though no fatalities have been reported.
