Tetons

Dangerous conditions exist. Multiple incidents occurred in all of our forecast areas yesterday afternoon. Snowmobilers in terrain above Ski Lake reported that an extremely large full depth hard slab avalanche released on a northeast aspect. The crown was reported to be up to 12 feet deep and 2,000 feet long. It took out mature trees. In the Snake River Range a skier was caught and deployed an airbag as he was being swept downhill. He was partially buried but not injured. A different slope failed after being crossed by the fifth skier. On Togwotee Pass two snowmobilers were caught and injured by a hard slab avalanche. Three people have been killed or seriously injured by avalanches in the past three days in Utah and Idaho. On steep slopes, dangerous full depth hard slabs could be triggered by a single person or more likely by a snowmobile. Conservative decisions regarding terrain selection are essential today.

A winter storm warming is in effect for Western Wyoming from 11 pm tonight thru 11 am Monday morning as a Pacific low pressure system moves through the region. Snowfall is expected to start late this evening and intensify during the day on Sunday. Six to ten inches of new snow could accumulate by Sunday evening. Overnight lows in the mountains will be in the mid teens rising into the low twenties on Sunday. South to southwesterly ridgetop winds will increase to 15 to 20 miles an hour.The general avalanche hazard is expected to be CONSIDERABLE on Sunday in the Teton, the Greys River/Southwest Trails, and Continental Divide/Togwotee Pass areas. New snow, falling upon crusts and surface hoar, will slowly increase the possibility for backcountry travelers to trigger new soft slabs and loose snow sluffs. Far more dangerous are the deep slab instabilities that plague the region. These hard slabs lie upon a base of weak, faceted snow, and could fail to the ground. A single person, and more likely a snowmobile, could trigger these avalanches even after a slope has been crossed multiple times. Conservative decisions regarding terrain selection will be essential tomorrow.