At the mid and upper elevations skiers and riders could triggered wind slab avalanches in steep avalanche starting zones where recent drifting has occurred. One of these slabs was triggered by a skier near the top of Albright Peak in Grand Teton National Park yesterday. The potential for humans to trigger very large persistent slab avalanches is becoming less likely, however the consequences of triggering one of these dangerous slides would be severe. Avalanches are unlikely at the lower elevations. Identify and avoid steep, wind loaded terrain features and evaluate the snowpack carefully to determine where old weaknesses still pose a threat.
Surface slabs formed by recent winds could be triggered by the weight of a single person. These wind slabs could be one to two feet deep.
In steep terrain some potential may remain for persistent slabs to be triggered by humans on buried layers of faceted snow. These slabs could possibly be triggered by a single person who hits a particularly weak spot on a slope, or more likely by a heavier trigger such as a snowmachine or following the initiation of a wind slab. These large to very large slab avalanches could be 3 to 5 feet deep at the mid and upper elevations. Persistent slabs with depths to 2 feet are unlikely to be triggered by humans at the lower elevations except on isolated terrain features.
Cloud cover will increase overnight ahead of a Pacific storm system that will begin to bring light to moderate intensity snowfall to the region on Saturday. Overnight lows in the mountains will be near zero before rising to around 10 degrees in the afternoon. Westerly ridgetop winds will back to the southwest at 10 to 20 miles per hour.Skiers and riders still have some potential of triggering recently developed surface slabs up to three feet deep in very steep, avalanche prone terrain above 7,500 feet. Persistent slab avalanches, with depths of three to five feet, remain a concern in some areas. Poor snowpack structure is likely to be found on slopes where the snowpack is less than six feet deep, and persistent slab avalanches are more likely to be triggered in these areas. Larger triggers, such as snowmobiles or the release of a surface slab, are more likely than an individual skier to initiate one of these slabs. Don’t let previous tracks lull you into thinking a slope is safe; they are not an indicator of stability.
