A few details from Friday’s snowmobile fatality have trickled in. It appears that the event took place east of Upper Palisades Lake on a south facing slope around an elevation of 9,000 feet. Four snowmobilers were caught; three were able to self-rescue, and one was fully buried. Yesterday, a significant slide was remotely triggered on the northeast facing aspect of Ullrs slide path off of 25 Short in Grand Teton National Park. A snowmobiler also triggered a large slide on a south facing aspect of Horseshoe Bowl at an elevation of 9,300 feet on Teton Pass.At the mid and upper elevations, skiers and riders will remain likely to trigger small to large wind slabs in steep, leeward terrain. Backcountry travelers could also trigger large persistent slabs on a variety of aspects and elevations. These dangerous slabs could step down from the release of a wind slab. Mountain temperatures are starting out around 10 degrees warmer than yesterday, and any extended periods of sunshine could increase the likelihood of triggering these slabs on sunlit aspects. Careful snowpack evaluation and conservative terrain choices will be your best tools for staying safe in avalanche terrain. Skiers and riders still have some potential of triggering small to large slab avalanches at the lower elevations.
Strong northwesterly ridgetop winds were sustained on Saturday, and wind slabs continued to form on leeward slopes. In steep, wind loaded terrain above 7,500 feet, backcountry travelers are likely to trigger these slabs with depths of one to three feet. Similar slabs up to 18 inches deep could be human triggered below 7,500 feet.
On steep avalanche prone slopes, large persistent slab avalanches could fail on buried weak layers of faceted snow. These dangerous slabs could be up to four feet deep above 7,500 feet. Below 7,500 feet, slab depths are expected to range from one to three feet. These slabs could be triggered directly by the weight of a single person or indirectly after the release of a wind slab.
A cold front will bring colder air to the region. Snow showers are possible overnight. On Monday temperatures will be in the single digits. Skies will become mostly sunny. Northwesterly winds will decrease to 10 to 15 miles per hour.Persistent weak layers continue to be failure planes for avalanche release. These weak layers include buried layers of surface hoar in areas with a deeper snowpack and a base of well-developed faceted snow in areas where the snowpack is less than four feet deep. Large slab avalanches could be triggered by backcountry travelers who venture onto steep avalanche prone slopes. These dangerous slabs could be 2 to 4 feet deep at the mid and upper elevations where the general avalanche hazard is expected to be considerable and up to two feet deep below an elevation of 7,500 feet where the general avalanche hazard is expected to be moderate.
