Transportation officials shut down I-70 between Vail and Golden in the late afternoon Friday because of wet, heavy snow and multiple accidents.
The American Red Cross opened a second shelter in Idaho Springs late Friday after its first shelter there filled to capacity with more than 300 people, said Jim Rettew, a spokesman for the organization's Mile High Chapter.
The stranded travelers didn't all get cots, but many got snacks, and most were in good spirits, he said.
"Some are trying to sleep, some are talking, some are eating, some are on the phone," Rettew said. "When this kind of thing happens, everyone just makes the best in trying circumstances."
The Colorado National Guard escorted a caravan of volunteers and supplies to the shelters after Clear Creek County declared an emergency and asked for state assistance. County officials were working to set up one or two more shelters in Georgetown.
It was unclear when the interstate would reopen. The spring storm had dumped up to 3 feet of snow on the foothills by Friday night but was starting to weaken, forecasters said.
The area was expected to see only another 2 to 5 inches through noon Saturday, said meteorologist Frank Cooper of the National Weather Service's Boulder office.
"It's very, very hard to speculate as to when traffic is going to be allowed back on the road," Colorado Department of Transportation spokesman Fritz Homann said early Saturday. "There seems to be a lull in the storm, but whether the second wave comes in as advertised will be anybody's guess."
Homann added that some motorists were still stuck on I-70 at Hidden Valley early Saturday, but crews were working hard to get them out.
"This is a big storm, but it is a spring storm in the Colorado Rockies, and that is something that CDOT has dealt with before," he said. "We have all our resources poised and ready to go."
Winter storm warnings across the state were expected to last until midday Saturday, with an additional 1 to 3 inches possible in the metro area and along the Front Range, the weather service said.
On Friday, heavy, wet snow closed highways, canceled flights, caused power outages and forced school closures in parts of Colorado and Wyoming. Snow accumulations of 3 to 4 feet were recorded in the mountains, with 4 to 6 inches measured in Denver.
United Airlines, the dominant carrier at Denver International Airport, canceled 76 flights. The airport urged travelers to check with their airlines before leaving home.
