Winter storm Cleon is heading toward the Pacific Northwest and, besides bringing chilly temperatures and cold winds, is expected to drop 2 to 3 feet of snow.

A winter storm dropped 30 inches of snow in Idaho Tuesday, and is forecast to bring temperatures well below zero elsewhere in the country as the week goes on.

Frigid temperatures swept across the northern Rockies and the northern Plains on Tuesday, and heavy sheets of snow are likely in Colorado, Utah, Wyoming, Montana and swaths of North Dakota. Parts of nine states were under winter storm warnings; nine other states were under various levels of advisories for current or future wintry precipitation.

Snow accumulation was racking up by Tuesday afternoon. By 3 p.m. ET, 30 inches of snow had fallen in Idaho's Saddle Mountain, and 22 inches had fallen north of Two Harbors, Minn. Stuart Mountain in Montana received 20 inches. Duluth had gotten 14 inches of snow and was forecast to receive another foot-plus as the flakes continued to fall.

"This has been a pretty helter-skelter storm today. It's snowing in a lot of places," said Nick Wiltgen, a meteorologist for weather.com. "Today we've got a band of snow extending from the Sierra Nevada in California all the way east to northern Michigan. But it's a fairly broken-up area of snow. There are some gaps where it's not snowing or only snowing extremely lightly."

The snow was wreaking havoc on Interstate 15 in Salt Lake City, where multiple accidents were reported. There were also road closures on Interstate 84 in northeastern Oregon due to car wrecks and snowy conditions and Interstate 90 in Wyoming was closed.

In the hardest-hit regions of the Rockies, the National Weather Service has predicted up to 15 inches of snow.

"There will be very significant snow out of this storm" said Jonathan Erdman, senior meteorologist at the Weather Channel. "If they don't have the Christmas spirit yet, they will by Wednesday. It will look like a postcard out there."

And yet snow is not all the winter blast has in store. Arctic air behind the storm is expected to slash southward across the Plains - bringing within it subzero temperatures.

Warm gusts of wind that could churn 80 mph were billowing through parts of Colorado on Monday ahead of the cold front. Temperatures in the Centennial State could plummet 50 degrees by Wednesday, according to NBC affiliate KUSA in Denver.

Denver has a 90 percent chance of snow overnight into Wednesday, The Denver Post reported, and could get up to 7 inches. Elsewhere in the state, in mountainous areas, one to three feet could fall by Wednesday afternoon, according to KUSA.

Montana saw the coldest of the temperatures on Tuesday, with single digits extending down to Yellowstone National Park. Starting Wednesday night through the weekend, temperatures of down to 20 degrees below zero are forecast for Montana, the Dakotas and Minnesota.

"We're looking ahead to the next phase of this system as another piece of energy comes out of the West and the cold air continues to ooze southward across the Plains states. They've already started posting winter storm watches across parts of Arkansas, most of Oklahoma and a small part of northern Texas in anticipation of what's going to be more of an ice event with some snow involved," Wiltgen said.

Sleet, freezing rain and hefty ice accumulations are possible with that next phase on Thursday and Friday, he said, and could damage power lines and bring tree branches and large limbs down, in addition to creating travel nightmares for commuters.

NBC News' Daniella Silva and the Associated Press contributed to this report.