Recent snowfall and strong southwesterly winds have created dangerous avalanche conditions. Since the early hours on December 23, there has been 13 to 15 inches of new snow with about 1.5 inches of water. This rapid loading has made it likely for human-triggered, small to large, slab avalanches on steep wind-loaded terrain and isolated terrain features above 8,000 feet. Natural avalanches are possible at the upper elevations. High wind speeds have probably caused snow surfaces to become stiff, and slabs could break above the trigger. The rapid loading is also stressing weak, faceted snow deep within the snowpack and causing these avalanches to be more easily triggered. Today, backcountry travelers should use cautions route-finding, careful evaluation of the snowpack, and conservative decision-making. And Merry Christmas!
New snow and strong winds continue to form wind slabs on leeward slopes. High wind speeds have likely formed hard slabs and transported snow into sheltered areas. These hard slabs may be too firm to ski cut and crowns could be lower in the start zones. Slabs could be up to 2 feet in depth.
The interface of the December 5th old snow layers, deeper in the snowpack, still remains a concern. The increased loading over these layers will add stress and the potential to trigger a deeper avalanche up to 3 feet in depth. Yesterday, riders near the Ditch Creek area, nearby Mount Leidy, were remote triggering large avalanches on these persistent weak layers.
( Discussion is generated from the previous day's afternoon forecast. )Pacific moisture in a westerly flow will continue to bring snowy weather to the forecast area. West to southwesterly winds are expected to increase overnight into the 40s with gusts into the 50s and then lessen into the 20s and 30s by tomorrow morning. The heaviest snowfall is expected to occur overnight, with an additional 6 to 9 inches for the Greys River area, 5 to 8 for the Teton Range, and 2 to 4 for the Togwotee Pass area by morning. Then throughout the day snowfall will lessen with an additional 3 to 6 inches across the region. Mountain temperatures will cool into the single digits and then warm into the teens. The avalanche hazard above 8,500 feet will remain Considerable on Christmas Day. Due to recent snowfall and sustained winds, dangerous avalanche conditions exist on steep wind-loaded slopes and isolated terrain features. On these suspect slopes, it will be likely for humans to trigger avalanches. High wind speeds may cause snow’s surface to become stiff and make it harder to trigger these newly formed slabs. If triggered, a slide could entrain new snow and grow in size. In isolated areas, it remains possible to trigger slab avalanches up to 4 feet deep on older weak snow, and the additional load continues to increase the stress on these layers.
