At the mid and upper elevations new snowfall continues to load a snowpack with poor structure. Persistent slab avalanches that lie upon weak layers of faceted snow could be human triggered in steep terrain with potentially serious consequences. Collapses and cracking are indications of instability and should be an alarm to avoid steep slopes. Last nights snowfall favored the west slope of the Teton Range. Grand Targhee has received a foot of new snow since early yesterday morning. In steep terrain loose snow sloughs and isolated pockets of soft wind slab, up to a foot in depth, are also a concern. Avalanches are unlikely at the lower elevations.
Persistent slabs up to three feet in depth lie upon a base of weak, faceted snow on a variety of aspects. These slabs could be triggered by the weight of a single person with depths to three feet. These slabs can remain unstable for days or weeks and pose a significant hazard to backcountry users.
Another storm is to bring snow Thursday night through Friday morning. As arriving moisture impacts and is pushed over the cold air that is in place over the region, periods of heavy snowfall are expected, particularly between 11pm and 5am. Over six inches of snow could fall by morning in the Tetons with slightly lower amounts expected in the other forecast areas. Two to four inches of snow is expected in the valleys. West-southwest winds are expected to have averages between fifteen and twenty five miles per hour. On Friday, periods of light snow are to continue and warmer air is to allow for mountain temperatures to reach the mid to upper twenties. Dangerous avalanche conditions exist. The general avalanche hazard is to be Considerable on Friday. New snow will add additional strain to a snowpack that is underlain by persistent weak snow layers. Human triggered avalanches will be likely in steep avalanche paths where early season snow lies and natural avalanches will be possible as slopes are loaded in the early morning and also as daytime warming and additional snowfall occurs. Slab depths to three feet are possible in the Teton area and depths to two feet are possible in the Southwest trails and Togwotee Pass areas.
