Up to 10 inches of new snow has accumulated in the past 24 hours, and very dangerous avalanche conditions have developed above 9,000 feet. Skiers and riders could easily trigger small to large wind slabs and loose snow sluffs in steep avalanche terrain above 7,500 feet, and natural activity will be possible. Much higher consequences are associated with large to very large persistent slab avalanches. These deadly slabs are likely to be triggered by backcountry travelers, and they have the potential of stepping down from a wind slab or releasing naturally. TRAVEL IN AVALANCHE TERRAIN IS NOT RECOMMENDED ABOVE 9,000 FEET. Below 9,000 feet, conservative terrain choices and cautions route finding will be essential for safe travel in avalanche terrain.
Southwesterly to westerly ridgetop winds at 15 to 30 miles per hour accompanied the new snow, and new wind slabs with depths up to 18 inches have formed above 7,500 feet. In steep, wind loaded terrain, human triggered slides will be likely, and natural activity may be possible.
Up to three quarters of an inch of snow water equivalent has been added to persistent weak layers since yesterday morning. On a variety of aspects above 7,500 feet, this new load has increased the likelihood of triggering persistent slab avalanches with depths ranging from two to four feet. Natural activity will also be possible. Below 7,500 feet, close to a half an inch of water weight accumulated, and skiers and riders could trigger similar slabs up to 18 inches deep.
( Discussion is generated from the previous day's afternoon forecast. )Periods of light to moderate snowfall will continue overnight before a drying trend begins Sunday morning. Overnight lows in the mountains will be in the low teens before rising into the upper teens during the day. Westerly ridgetop winds at 20 to 30 miles per hour will veer to the northwest and decrease to 5 to 15 by morning.Dangerous avalanche conditions exist in the Teton and Southwest Trails forecast zones, and the general avalanche hazard is expected to remain Considerable on Sunday. While skiers and riders could trigger small pockets of newly develop wind slab near upper elevation ridgelines, the primary concern will be persistent slab avalanches failing on crusts and faceted snow from the December 11th interface. In steep, avalanche prone terrain above 7,500 feet, skiers and riders could trigger these large to very large slabs on a variety of aspects. The underlying persistent weak layers and sliding surfaces vary significantly across the landscape; some slopes are stable, others are not, and it is difficult to distinguish between the two. Conservative terrain choices and route finding will be essential for safe travel in avalanche terrain on Sunday.On Togwotee Pass, where a fraction of the snowfall has accumulated since the 11th, the general avalanche hazard is expected to remain Moderate above 7,500 feet. There, backcountry travelers have the potential of triggering small to large persistent slabs on steep, avalanche prone slopes.
