Up to 15 inches of new snow has accumulated in the past 24 hours, and very dangerous avalanche conditions have developed at the upper elevations. Skiers and riders could easily trigger small to large wind slabs and loose snow sluffs in steep avalanche terrain at the mid and upper elevations, 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. Between 7,500 and 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 varying from one to two feet have formed above 7,500 feet. In steep, wind loaded terrain, both human triggered and natural activity will be likely.
Over an inch of snow water equivalent has been added to persistent weak layers since yesterday morning. On a variety of aspects at the mid and upper elevations, 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. In the lower elevations, close to a half an inch of water weight accumulated, and skiers and riders could trigger similar slabs up to 18 inches deep.
Expect partly cloudy to mostly clear skies overnight and through the day on Monday as a broad trough begins to track across the southwestern US, and southwesterly flow aloft develops over the region. Overnight lows in the mountains will drop into the single digits before rising into the teens during the day. Sunday’s warmup will be followed by cooler temperatures, and the general avalanche hazard is expected to be Considerable above 8,000 feet in the Teton and Southwest Trails forecast zones on Monday. While the potential remains for skiers and riders to trigger small to large wind slabs, the primary hazard will be large to very large persistent slab avalanches failing on crusts and faceted snow from the December 11th interface. In steep terrain up there, backcountry travelers could trigger these 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 cautious route finding will be essential for safe travel in avalanche terrain on Monday.In the Togwotee Pass forecast zone, the general avalanche hazard is expected to be Moderate above 8,000 feet. On steep, avalanche prone slopes, backcountry travelers have the potential of triggering small pockets of wind slab along with large persistent slabs.
