Millions of Americans are bracing for the impact of dangerous weather

About 70 million Americans are under winter weather watches and wind advisories on Saturday as a winter storm moved across the Plains states and into the Midwest. Three areas of the country are expected to get heavy snowfall through Monday night: the California mountains, the Upper Midwest and the Northeast, the National Weather Service said.

In a separate storm system, rain and thunderstorms are expected in the Lower Mississippi, Tennessee, and Ohio Valleys, the National Weather Service said.

It warned travel could become impossible in some places.

“The timing couldn’t be worse,” CBS News climate change and weather contributor Jeff Berardelli said.

The National Weather Service warned that “high winds are expected, and blizzard warnings are in effect for parts of the Northern/Central Plains. Dangerous conditions will make travel almost impossible. High Wind Warnings and Wind Advisories are in effect for the Central/Southern Plains, south of the snow impacts.”

Whiteout driving conditions were treacherous north of Minneapolis. And similar scenes are likely to play out for millions of others as the storm moves east with heavy snow, strong winds and areas of wintry mix.

One storm-related death has been reported in South Dakota. Ten inches of snow were reported in Rapid City, South Dakota.

Roads were closed Saturday across eastern and southern Wyoming due to whiteout conditions. The National Weather Service in Wyoming reported 4 inches of snow fell in Cheyenne from 7 p.m. Friday through 10 a.m. Saturday on top of a foot of snow that fell before Thanksgiving. Wind gusts up to 50 mph created ground blizzards.

National Weather Service Meteorologist Andrew Lyons said a wind gust of 77 mph was reported in the mountains between Cheyenne and Laramie. All roads in and out of Casper were closed Saturday morning, including the entire 300 mile stretch of Interstate 25 in Wyoming.

Farther east, blizzard conditions Saturday are buffeting the High Plains and around Duluth.

American Airlines issued a weather alert for more than 40 airports, including the New York and Philadelphia travel hubs. The current alert allows travelers to rebook their flights without fees.