NATIONAL PARKS -- Snowmobiles and metal-tracked vehicles are being prohibited between West Yellowstone and Old Faithful in Yellowstone National Park because of a lack of snow on the ground.

Restrictions were put in place Tuesday morning because large portions of visible pavement on many areas along the road, Yellowstone park officials said in a statement.

“This results in unsafe operating conditions for snowmobiles and snowcoaches with ski steering,” the statement said.

Commercial snowcoaches with rubber tracks or commercial wheeled vehicles are still permitted.

To no one’s surprise, the unusually warm weather and lack of snowfall is the culprit, Yellowstone spokeswoman Amy Bartlett said Wednesday.

“It’s just been such a long stretch of above-normal temperatures and not much snow,” Bartlett told the Jackson Hole News & Guide. “It’s been so warm. It’s definitely not normal.”

The weather, Bartlett said, so far has not affected winter travel in other portions of the park — including the highway leading north from Jackson Hole through the South Entrance.

Conditions on other interior Yellowstone roads remain “fair to good,” Yellowstone’s statement said.

“Park staff members continue to closely monitor oversnow road conditions and weather forecasts,” it read. “Improving or deteriorating conditions may prompt further changes to motorized oversnow access in the coming days.”

More winterlike conditions were expected to return Friday and Saturday with cold and snow predicted by the National Weather Service.

Interior roads in the park would ordinarily be open to winter travel through early to mid-March.

A fast-diminishing snowpack isn’t the rule everywhere in Yellowstone.

“There are areas in the park that are at or above their normal snow levels,” Bartlett said.

A 7,860-foot monitoring site at the Lewis Lake Divide showed that the snow depth Wednesday in southern Yellowstone’s high country was about 62 inches. Measured by its water weight, the snowpack was 89 percent of the long-term median, according to the University of Wyoming’s online Water Resource Data System.

The warmth so far hasn’t affected normal winter activities in Grand Teton National Park, spokeswoman Jackie Skaggs said.

“We don’t really have any problems here as a result of the warmer temperatures,” Skaggs said.

The freeze-thaw cycle has made for good “crust cruising” on skate skies, she said, and ice fishing is still occurring on Jackson Lake.