Dangerous avalanche conditions exist above an elevation of 7,500 feet. Four to eight inches of new snow has fallen in the past 24 hours and up to 20 inches of snow with over two inches of moisture has fallen since Tuesday. Southwest winds veered to the west and increased overnight. This snow has been falling on an early season snowpack that has poor structure. A weak layer of faceted snow that was buried on Thanksgiving is widespread and may become unstable due to this new load. At the mid and upper elevations human triggered avalanches are likely in steep terrain. Natural avalanche activity is possible. Avalanche types include loose snow sloughs in cliff areas and steep terrain, fresh soft wind slabs along the leeward side of higher ridge crests and deeper slab avalanches that can fail on a persistent weak layer of faceted snow and crust. Careful snowpack evaluations and conservative decisions are essential for safe travel in avalanche terrain. Watch for areas of unstable snow on isolated terrain features at the lower elevations.
At the mid and upper elevations slab avalanches one to three feet in depth are likely to be triggered by humans in steep wind loaded avalanche starting zones and could release naturally.
( Discussion is generated from the previous day's afternoon forecast. )Moderate snowfall is to continue tonight with lingering showers expected through Saturday. Highest accumulations are, again, expected in the Tetons where over six more inches may fall. In the other forecast areas three to six inches is expected. Temperatures are to be slightly cooler while southwest to west winds have averages between fifteen and twenty degrees. The avalanche danger ratings for Saturday will be dependent upon the actual amounts of snow, wind, and weather that is received overnight and where. If enough snow and associated moisture occur, the danger will rise to Considerable. If so, the chance for humans to trigger the persistent slab problem will increase as will the likelihood to initiate loose snow sloughs and very soft surface slabs in steep terrain. Once moving these smaller surface events could also cause failure of the deeper weakness. Avalanches below 8000 feet remain unlikely excepting small, isolated pockets in very steep, shaded terrain.
