DES MOINES, Iowa — A fierce winter storm was moving into the nation’s midsection today, promising to wallop the region with heavy snow and strong winds.

Officials were warning residents in parts of the west and Midwest to stay close to home.

“Anybody traveling tomorrow morning is really taking a huge risk I would say — a risk of being stranded and not having anybody be able to help you for 6 or 12 hours, probably,” Karl Jungbluth, a meteorologist with the National Weather Service in Johnston, Iowa, said today.

The storm already blanketed much of the Mountain West with snow and drenched Southern California with rain. In the Phoenix area, fierce wind brought down power lines, left four hospitals temporarily without power and created wide outages.

Ice was the problem in Oklahoma, where Interstate 40 was closed for about 25 miles in western Oklahoma between Clinton and Elk City, leaving truckers to wait out the storm.

Mitch Dodson, a trucker hauling soda pop out of Durango, Colo., to Virginia, was waylaid at the Travel America plaza near the town of Sayre.

“It’s just a sheet of ice from Amarillo to here,” Dodson said. “It’s a disaster.”

Misty Willis, the assistant manager at the plaza, said I-40 had become a “skating rink.”

“I drove 20 miles an hour to get here,” she said. “I literally slid into my parking space.”

In Schaller, Iowa, Sparky’s One Stop gas station assistant manager Rose Jansen said they were bracing for the storm.

“Snow and lots of it!” Jansen said. “We’ll be here, no matter what.”

Jungbluth said a “classic, big, deepening winter storm” was affecting more than a dozen states. He said it would take shape over Oklahoma and Kansas today, then swing northeast through Missouri and the Upper Midwest before heading toward Lake Michigan. A foot or more of snow was expected in parts of Iowa, Illinois and Wisconsin. Wind gusts of up to 40 mph could create snow drifts of 8-15 feet.

Kent Barnard, a spokesman for the Minnesota Department of Transportation’s Twin Cities district, said preparations for the storm began well before dawn today as crews treated curves, bridge decks and other slippery spots with chemicals.

The storm had hit much of the West on Monday, from subzero wind chills in Washington state to heavy snow that closed schools and government offices in Reno, Nev. Big rigs were left jackknifed across highways in several states.

In New Mexico, two people were killed in traffic accidents blamed on slick conditions.

The National Weather Service said the upper elevations of the Sierra mountains could get up to 3 feet of snow, with up to 4 feet forecast for the mountains of southern Utah.

Reno schools closed, and many state government workers were told to stay home. Several flights into and out of Reno-Tahoe International Airport were delayed or canceled. Chains or snow tires were required across the region.

“Motorists are going to have to chain up,” Trooper Chuck Allen with the Nevada Highway Patrol said. “Otherwise, we end up with a parking lot.”

In northern Arizona, state officials closed parts of Interstate 17 and I-40, saying early today that some stretches of the highways were snow-packed and visibility levels were near zero. Department of Transportation spokesman Rod Wigman advised people to stay home if possible as the brunt of the storm sweeps through.

“When the sun goes down, people need to go home,” Wigman said.