Travelers crossing Teton Pass in coming days can expect “difficult if not impossible” conditions as the winter’s first big storm hits.

The National Weather Service used those words Thursday as it issued a winter storm watch. Bad weather is expected to begin arriving in Jackson Hole this afternoon and to continue Saturday and Sunday. The change in weather is predicted to start slow and gain force by Sunday, when high winds and falling temperatures are expected.

The weather is likely to be much less severe on the valley floor, but will worsen quickly as you gain elevation, said meteorologist Dave Lipson, based in the weather service’s Riverton office.

Jackson meteorologist Jim Woodmencey agreed.

“It’s going to be rain mostly for town, the valley, but we’re right on the cusp,” Woodmencey said. “You won’t have to climb elevation a lot to get to snow.”

Lipson added: “I think you’ll see the rain-snow line, at the highest, at about 7,000 feet. And you’re going to see a more significant accumulation above 7,500 feet.”

Lipson said the valley floor can expect “when all’s said and done, about four inches of snow — not accumulated, but maybe an inch on the ground that melts, then another inch falling.”

But between Jackson, at 6,237 feet, and Teton Pass, at 8,432 feet, there’s a world of weather difference, the forecasters said.

“Teton Pass should see potentially as much as two feet, or a little more than that,” Lipson said.

“It’s going to be a considerable amount of snow,” Woodmencey said. “Two feet or more is not out of the question.”

The weather service is predicting that by Sunday there will be winds of 40 mph at higher elevations, with gusts at 70 mph: “You really need to anticipate a lot, at least a couple of hours, of really strong winds late Sunday afternoon and evening,” Lipson said.

The wind and colder temperatures Sunday promise blowing snow and drifting and dangerous driving on Teton Pass.

“It would probably be a good weekend not to be driving around up there,” Woodmencey said. “But that’s where everybody congregates” for the powder skiing.

Colder weather Sunday might also change things at lower elevations, Woodmencey said.

“Sunday night, Monday morning we will accumulate snow in the valley,” he said.

Despite hazards, the storm will be good for business, Woodmencey said.

“There’s going to be a lot of heavy, wet snow for the mountains,” he said, “to make a good base for the rest of the winter.” Woodmencey’s forecast can be found at mountainweather.com.