At the upper elevations slab avalanches formed by southwest to westerly winds pose a hazard in northerly facing avalanche paths. These slabs lie upon a persistent weak layer of faceted snow and a hard rain crust that formed in October. The hazard is believed to be greater in the Salt River and Snake River Ranges where 24 hour snowfall totals are significantly greater than in the Wyoming Range. Natural avalanche activity is possible and human triggered slab avalanches are likely in steep wind loaded avalanche paths. Avalanches are unlikely below an elevation of 9,000 feet where snow depths remain shallow and the October crust is absent at the base of the snowpack.
At the upper elevation soft slab avalanches up to two feet in depth could be human triggered or release naturally in steep wind loaded avalanche paths underlain by a persistent weak layer of faceted snow that lies upon a hard October rain crust.
( Discussion is generated from the previous day's afternoon forecast. )Atmospheric instability is expected to produce convective snow showers over the mountains tonight. The next upper level disturbance will move into the region during the day. Tonight's snow shower activity is expected to favor the west slope of the Teton Range and the higher elevations where several inches of new snow accumulation or more is likely. Tomorrow’s disturbance should bring another 1 to 5 inches to the region. Temperatures will remain in the teens at the higher elevations, in the 20s at the mid elevations and should rise to near freezing in the valleys during the day. Winds along the high ridge crests will be westerly at 20 to 25 with gusts to 40 miles per hour.The general avalanche hazard is expected to be CONSIDERABLE at the upper elevations in the Teton area and MODERATE at the upper elevations of the Continental Divide/Togwotee Pass and Southwest Trails/Grey’s River areas. The hazard is expected to be LOW at the mid and lower elevations. Natural and human triggered avalanches are possible at the upper elevations and will be large enough to cause serious injury or death. Shooting cracks and whooping sounds associated with a collapse of a weak layer are signs of instability. Potential exists for dangerous slab avalanches to be remotely triggered from runout zones. A conservative approach to terrain selection is essential in steep terrain where a weak layer of faceted snow peersist on the October rain crust.
