Yesterday, a snowmobiler who deployed an airbag died in an avalanche near Sheep Pass in the Salt River Range and the second skier to cross a slope was partially buried in a terrain trap on Teton Pass. At this point, the information on the fatality is limited. Snow that fell during the past week lies upon persistent weak layers. The weight of a single person can trigger a slab avalanche on steep avalanche-prone terrain. At the mid and upper elevations these slab avalanches are large enought to fully bury or seriously injure a person. At the lower elevations, where poor snowpack structure exists, small avalanches are possible on steep slopes. This type of avalanche hazard is best managed by terrain assessment skills and conservative terrain choices. Evaluate steep slopes carefully and anticipate the potential consequences of triggering a large slab avalanche or a slab avalanche of any size in terrain traps or on slopes with low snow hazards that can cause serious trauma.
At the mid and upper elevations, small to large slab avalanches formed by southwest to west winds could be human triggered. These slabs could be one to two feet deep. At the lower elevations these slabs are smaller and generally about a foot deep. Gusty winds and additional snow could increase the likelihood and sensitivity of these slabs.
After a brief lull overnight, northwesterly flow aloft will bring another round of snowfall to the region with the Tetons being favored over the other two forecast areas. Overnight lows in the mountains will be in the mid-teens before climbing to near 30 in the afternoon. Westerly ridgetop winds will range from 20 to 30 miles per hour.On Sunday, the general avalanche hazard is expected to be Considerable in the higher elevations of the Teton and Southwest Trails forecast zones. Continued snowfall and strong winds will result in dangerous avalanche conditions. While skiers and riders could trigger slab avalanches on density breaks within the recent snowfall, the primary concern for Sunday will be persistent slab avalanches. Skiers and riders could trigger these slides in steep terrain at all elevations, but the highest consequences will be on upper elevation slopes where these slabs could be up to 30 inches deep. In lower elevation terrain, smaller slabs around a foot deep will be possible. The general avalanche hazard is expected to remain Moderate on Togwotee Pass where backcountry travelers have the potential of triggering persistent slabs with depths ranging from one to two feet.
