A powerful winter storm swept across Colorado on Friday, forcing the cancellation of nearly 600 flights at Denver airport, closing parts of Interstate 70 and sparking a run on grocery stores before the worst weather descended.

The eastbound storm brought blizzard warnings to eastern Colorado and winter storm warnings to southeast Wyoming, western Kansas and western Nebraska.

It stretched as far south as New Mexico, where the Department of Transportation reported difficult driving conditions on several state highways because of icy snow.

Cindy Williams, who works at a truck stop about 80 miles west of the Kansas-Colorado border, said the parking lot was filling up because of road closures.

"There's nowhere to go," she said.

One of the hardest hit areas was Evergreen, west of Denver, where 3 feet of snow fell. Snow totals were mounting rapidly along the Front Range and in eastern Colorado, where 10 inches fell in Denver and 14 inches in Boulder.

Shoppers began clearing the shelves of staples on Thursday, hours in advance of the storm, said Kristine Staaf, a spokeswoman for Safeway grocery stores.

"They were coming in droves for staples -- milk, eggs and bread," she said. Most stores were restocked by Friday, except for stores on the Eastern Plains, she said.

The storm forced the cancellation of nearly 600 arriving and departing flights scheduled through Friday night at Denver International Airport. The total marked about 35 percent of its daily average of 1,700 flights.

Southwest Airlines canceled all of its flights through the airport until 4 p.m. because of the storm. The airline said it wanted to mitigate the impact of the storm on its operations elsewhere across the country.

Meanwhile, truckers and other travelers were stranded when snow closed portions of Interstate 70 on Colorado's Eastern Plains. The eastbound highway was closed from an area east of the airport to Limon. Westbound lanes were closed from near the airport all the way Burlington, near the Kansas line. The closures were expected to remain in place overnight.

The National Weather Service said snow was falling at 2 inches an hour on the Eastern Plains, producing blizzard conditions in some areas. A band of heavy snow stalled in central Nebraska, dumping nearly 13 inches in some spots.

The Colorado Avalanche Information Center issued a warning through Friday east of the Continental Divide, saying 2 feet of snow or more could overwhelm a weak snow pack, with natural and human-triggered avalanches likely.

Elsewhere, the University of Colorado closed its Boulder campus, affecting about 30,000 students. Gov. John Hickenlooper told state workers in the Denver metro area to stay home until 10 a.m. unless their jobs involved health and safety.

Colorado lawmakers canceled legislative work, and many school districts announced they would be closed, including the two largest, in Jefferson County and Denver.

Stores in Denver reported brisk business Thursday night.

"The cheese wall is hammered, bread's kind of hammered, milk's kind of low," said Aaron McFadden, a manager at a King Soopers store.

Ted Vaca at Argonaut Liquor said customers were snapping up all kinds of drinks.

"It was more like a Friday than a Thursday," he said.

The snowfall didn't slow shopping at Ewoldt's Grocery store in Thedford, Neb., about 300 miles northwest of Omaha.

Clerk Velma Burns said people were shopping a little heavier than normal. For her customers, shopping for "the Super Bowl's really bigger than the snowstorm," she said.

(Copyright 2012 by The Associated Press. All Rights Reserved.)

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