Six to ten inches of light density snow has fallen in the past 24 hours. Overnight, westerly ridgetop winds increased to 15 to 20 miles per hour and temperatures have warmed a few degrees. This combination has created an upside-down snowpack and dangerous avalanche conditions. Backcountry travelers are likely to trigger wind slabs in steep, wind-loaded terrain. In more sheltered areas, loose snow sluffs are also possible. These slides also have the potential to step down to faceted snow near the base of the snowpack above 7,500 feet. A conservative approach to both terrain selection and decision making will be essential for safe travel in avalanche terrain.
Skiers and riders could easily trigger new and recently developed soft wind slabs on all aspects and elevations. These slabs could have depths of one to two feet and fail on old hard surfaces or density breaks within the recent snowfall. Beware of steep terrain with obvious areas of wind loading. Several of these wind slabs have been reported in recent days on a variety of aspects and elevations.
Above 7,500 feet, hard slabs with depths to four feet lie upon persistent weak layers of faceted snow. Since Wednesday night, around an inch and a half of snow water equivalent has been added to the snowpack. Large triggers, such as groups of people, may be needed to trigger one of these slides. However, the weight of a single skier or rider could act as a trigger. The release of a wind slab could also step down to these basal facets. If triggered, these slabs will carry high consequences.
( Discussion is generated from the previous day's afternoon forecast. )A Winter Weather Advisory has been issued for Western Wyoming by the National Weather Service. Overnight, the mountains could receive an additional five to ten inches of new snow with the Tetons seeing highest amounts. Nighttime lows in the mountains will be around ten degrees before rising to near 20 during the day. Westerly ridgetop winds will increase to 25 to 35 miles per hour overnight before relaxing during the morning hours as snowfall intensities decrease.The general avalanche hazard is expected to be Considerable on Sunday. If snowfall amounts or wind speeds are significantly higher than forecasted, the hazard could increase to High. Two avalanche problems will confront skier and riders on Sunday. Wind slabs, with depths of one to three feet, are likely to be triggered by backcountry travelers and could release naturally. The second threat is either deep persistent slab in the Tetons and Greys River area or persistent slab in Togwotee Pass forecast zone. If triggered, these slabs will result in high consequences and could be up to six feet deep in the Tetons, four feet in the Togwotee Pass area and five feet in the Greys River forecast zone. Large triggers, such as groups of people, may be needed to trigger one of these slides, particularly in the Tetons where the persistent weak layers are the deepest and most difficult to impact. The release of a wind slab could also step down to these basal facets. A conservative approach to both terrain selection and decision making will be essential for safe travel on Sunday.
