On west through north to east aspects at the upper elevations and on northerly aspects at the mid elevations new snow has been accumulating on slick or faceted old snow surfaces since Wednesday evening. In this terrain small to large slab avalanches could be human triggered on those old snow surfaces. Heavy snowfall accompanied by gusty southwest winds will be increasing the avalanche hazard in that terrain today. Monitor conditions and evaluate snow and terrain carefully. Avalanches are not likely in terrain where the recent new snow has accumulated on bare ground. These areas include all aspects below an elevation of 8,000 feet and southwest through south to southeast aspects up to an elevation of 10,000 feet.
At the upper elevations and on northerly aspects down to an elevation of 8,000 feet dense wind slabs could be human triggered in steep terrain on old snow surfaces. These slabs could be up to two feet deep and will be gaining depth and volume as the day progresses.
A most and rather warm storm system will bring moderate to heavy snowfall to the region and will be accompanied by strong westerly winds. A winter storm warning, issued by the National Weather Service, remains in effect. New snow totals of 1 to 2 feet are expected in the mountains during the next 24 hours. Deeper amounts are possible in the Teton Range. Temperatures will remain in the 20s at the higher elevations. A mix of rain and snow is expected at the lower elevations. West to southwest wind will continue at speeds of 25 to 30 with gusts to 45 miles per hour. The general avalanche hazard is expected to increase to CONSIDERABLE at the upper elevations (9,000 to 10,500 feet). Dense slab avalanches two to four feet in depth could be human triggered or release naturally on slick old snow surfaces. These dangerous avalanches are likely to be un-survivable. Slab avalanches may also fail on density differences within the new snow. At the mid elevations the general avalanche hazard is expected to be MODERATE. Human triggered small to large slab avalanches that fail on old snow surfaces are possible on northerly aspects between the elevations of 8,000 to 9,000 feet. Careful snowpack evaluations and a cautious approach to terrain selection will be essential for safe travel in avalanche terrain at the mid and upper elevations. Avalanches are unlikely below an elevation of 8,000 feet where the general avalanche hazard is expected to be LOW.
