30 million in path of winter storm

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(CNN) — It’s no Donner Pass, eat-the-driver-next-door situation, but a big winter storm threatening 18 states forced California authorities to close portions of a snowed-under interstate and a state highway in Kern County.

What California’s highway department described as “hundreds of vehicles” got stuck on State Route 58 between Bakersfield and the community of Tehachapi on Tuesday night, California’s highway department reported, and at least a few big rigs and some cars remained Wednesday morning, a highway patrol dispatcher said.

The agency closed a portion of Interstate 5 because of icy conditions early Wednesday morning, according to its website. The California Highway Patrol tweeted around 10 a.m. (1 p.m. ET) that the highway had reopened, restoring the main route between norther and southern parts of the state.

It’s all part of a major winter storm that’s now moving out of California and toward the central Plains and Midwest, where some places could see more than a foot of snow between Wednesday and Friday, CNN meteorologist Brandon Miller said.

All told, about 800,000 square miles in 18 states were under some form of watch or warning related to the storm, Miller said. About 30 million people live in the covered areas, he said.

The biggest threat of heavy snow lies in parts of Kansas, Nebraska and Missouri, with the possibility of whiteout conditions in some places, he said.

In Kansas, the National Weather Service was predicting as much as 18 inches of snow. The agency said parts of Nebraska could see more than a foot of snow, with drifts making some roads impassable.

Forecasters were predicting as much as 2 inches of snow in St. Louis, with the precipitation turning into sleet and freezing rain Thursday. The conditions will have “a significant impact on travel,” the weather service warned.

North of where the biggest snow will fall, Chicago could receive what would be its largest single snowfall of the year — 4 inches, Miller said. The city usually gets up to 4 feet of snow a year. So far this year, only about a foot has fallen, he said.

South of the snow belt, dangerously icy conditions are possible in parts of of northern Arkansas and southern Missouri, he said.

Elsewhere, severe thunderstorms moving in from the Gulf of Mexico are expected to dump from 2 to 6 inches of rain over New Orleans, Louisiana, and Montgomery, Alabama, according to CNN’s weather center, before rolling up toward Atlanta.

The torrential rains could lead to significant river flooding near the Gulf, as flood watches are still in effect from last week’s heavy rains.

Heavy winds, hail and tornadoes are possible, the National Weather Service says. Downpours are expected to continue into Friday.

By Michael Pearson and Ben Brumfield, CNN. CNN’s Ivan Cabrera and Dave Hennen contributed to this report.