Backcountry travelers venturing into steep, wind loaded avalanche terrain at the mid and upper elevations could trigger recently developed wind slabs one to two feet in depth on a variety of aspects. Persistent slabs up to three feet deep remain a concern on northerly facing slopes above 9,000 feet. These deeper slabs could be triggered directly by skiers and riders, or indirectly by shallower wind slabs stepping down to the faceted snow near the base of the snowpack. Three to six inches of dense snow fell in the past 24 hours adding weight to the snowpack. Periods of snowfall and southwesterly ridgetop winds will continue to load the snowpack, increasing the sensitivity of human triggers to these slabs. Avalanches are unlikely at the lower elevations. During initial avalanche hazard reduction at the Grand Targhee Resort, explosives pulled out a hard slab on a southeasterly aspect with a crown depth of 40 inches. Targhee remains closed to uphill traffic as they prepare for a Friday opening.
Strong west-southwesterly to northwesterly winds over the weekend created dense wind slabs up to two feet in depth on leeward aspects. Backcountry travelers could trigger these slides in steep, wind loaded avalanche terrain. These slabs are mostly likely to be found in exposed terrain near ridgelines. Avoid slopes where the snowpack has a hollow, drum-like feel.
Weak, faceted snow persists at the base of the snow pack on northerly and shaded aspects above an elevation of 9,000 feet. These dense slabs, up to three feet in depth, could be triggered by skiers and riders on this persistent weak layer. Previous tracks on these slopes may not be an indication of stability.
The combination of a stream of Pacific moisture and an arctic cold front will produce periods of heavy snowfall overnight with four to eight inches of new snow in the mountains possible by Thursday morning. Cloud cover will then decrease during the day. Overnight lows up high will be in the mid teens before rising to near 20 during the day. Ridgetop winds will veer to the north at 10 to 20 miles per hour.Above 7,500 feet, the general avalanche hazard is expected to be MODERATE on Thursday. On northerly aspects above 9,000 feet, skiers and riders could trigger persistent slabs failing on faceted snow near the base of the snowpack. Abundant settlement followed by cooling temperatures may balance out the increased load in respect to the likelihood of triggering, but the consequences of being caught have increased with the higher density and depth of these two to four foot slabs. Backcountry travelers could also trigger recently developed wind slabs one to two feet deep in steep, wind loaded terrain. These surface slabs could step down to the basal weak layer as well. The general avalanche hazard is expected to be LOW below an elevation of 7,500 feet. The Grand Targhee Ski Resort will be closed to uphill traffic in preparation for a Friday opening.
