Yesterday, a snowmobiler was caught and killed in a large avalanche in the Squaw Creek Drainage located in the Grey’s River area southeast of Alpine. The Bridger-Teton Avalanche Center will be conducting an investigation of this accident. In the Teton forecast area, a break in the clouds yesterday allowed for a few observations of large avalanches that occurred during the end of this most recent storm. At the upper elevations, backcountry travelers could encounter dangerous avalanche conditions today, and when traveling in avalanche-prone terrain it is possible to trigger large avalanches. Expert snowpack and terrain analysis skills are essential for safe travel in avalanche terrain, and if triggered slides could run long distances.
Persistent slab avalanches could be human-triggered at the lower elevations and at the mid and upper elevations in areas with shallower snow depths, where poor structure of faceted snow lies at the base of the snowpack. These persistent slabs are likely to range in depth from 2 to 5 feet, and could also be triggered by the release of a wind slab.
At the higher elevations, northwest winds from yesterday formed wind slabs on leeward slopes. Slab formation from a few days ago was caused by southwest to west winds. On wind-loaded terrain features, slab avalanches one to three feet deep could be human-triggered on density breaks and firm wind-packed snow surfaces.
Conditions will be mostly dry except for some isolated snow showers until midnight. The next storm system is fast moving and will bring snow that could become heavy at times between 2 am and noon. After a lull in the precipitation a second wave of moisture, which is slower moving, will arrive in the evening. Winds will back to the southwest, increase to 25 miles per hour with higher gusts and bring warmer air into the region. Tomorrow's temperatures are expected to rise into the 20s.In the Greys River and Togwotee Pass areas conditions are dangerous and are likely to remain that way. Recent new snow lies upon older faceted persistent weak layers and is unstable on steep slopes. Slab avalanches can be easily triggered by the weight of a person. The new snow is deep and therefore this situation can produce large, dangerous slab avalanches that could be three to six feet deep. In these areas the general avalanche hazard is expected to be considerable. In the Teton forecast area visibility has been limited. Several very large slab avalanches are known to have occurred in response to recent snowfall and wind events. With more snow and wind in the forecast conditions are expected to remain dangerous at the upper elevations where the general avalanche hazard is expected to be considerable. A moderate hazard is anticipated at the mid and lower elevations. Large to very large slab avalanches are possible and could be 2 to 5 feet deep.
