Persistent weak layers are present in the snowpack. The storm that occurred two days ago deposited dense wind driven snow onto a layer of well-developed surface hoar. That new snow and strong winds also increased and redistributed the load on persistent weak layers of faceted snow deeper in the snowpack that formed much earlier in the season. Wednesday’s storm triggered the natural release of a large slab avalanche on the east face of Lava Mountain and on mulitple slopes in the Teton Range. Similar events could be triggered by humans today. Snowpack stability assessments may be inconclusive in these conditions and the consequences of your terrain choices could be fatal. Whumphing and the collapse of the snowpack are strong indications of instability.
Persistent slab avalanches could be triggered by the first person on a slope or on a slope with multiple tracks. These dangerous slabs could be triggered on a variety of aspects. They could be 2 to 4 feet deep above an elevation of 7,500 feet and up to 2 feet deep below that elevation.
( Discussion is generated from the previous day's afternoon forecast. )Clear skies and light winds under a high-pressure ridge will promote the development of a temperature inversion. Overnight lows will be in the single digits below zero in the valleys and in the single digits above zero in the mountains. Daytime highs will rise into the 20’s. Winds will be northwest and decrease from 20 to 10 miles per hour.In areas where the snowpack is deep, like the higher elevations of the Teton Range, the persistent weak layer that has been the failure plane for large to very large avalanches is going to become less sensitive to human triggers. That said, the potential remains for a person to trigger a very large and destructive slab avalanche with severe consequences in these areas. These deep persistent slab avalanches could be 3 to 6 feet deep. In areas where the snowpack is shallower large slab avalanches are more likely to be triggered by humans. These persistent slab avalanches could be 1 to 4 feet deep. In these conditions, terrain analysis skills and conservative terrain choices are essential for safe travel in avalanche terrain. As our snowpack gradually gains strength, the distribution of the hazard may become more isolated in some areas and some slopes may require larger triggers, like snowmachines, to initiate the failure of a dangerous slab avalanche. Snowpack stability assessments may be inconclusive in these conditions and the consequences of your terrain choices could be fatal. The general avalanche hazard is expected to be moderate in the Togwotee Pass and Teton areas and considerable in the Greys River area.
