Human triggered avalanches are likely today at mid and upper elevations with the potential for deeper, weak layers to also crack and fail. Recently formed wind slabs which developed yesterday will continue to grow through the day. These slabs are likely to be sensitive to triggering by a skier or rider and could be one to two feet thick. If these avalanches involve a more deeply buried persistent weak layer, an avalanche three to four feet could result. Dangerous avalanche conditions such as these require careful routefinding and snowpack evaluation. Low elevation have a very limited snowpack making avalanches unlikely there.
More new snow and wind will continue to build wind slabs throughout the day. These slabs will be sensitive to triggering and may fail naturally, especially near ridgetops or heavily loaded lee areas. Wind slabs could be up to two feet thick but may also break more deeply on weak snow closer to the ground. Beware of steep, wind loaded areas that shows signs of wind loading.
Weak layers deeper in the snowpack may fail under weight of a passing skier or rider or the stress of new snow and wind loading. Natural avalanches on this layer will be increasingly possible. Avalanches on this problem layer could be three to four feet deep.
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.
