Salt River and Wyoming Ranges

Conditions remain dangerous above an elevation of 8,500 feet. Natural and human triggered slab avalanches occurred yesterday on west through north to east aspects. Some were triggered from flat areas by skiers on approach. Large slab avalanches released naturally in terrain that has not experienced slide activity in over 20 years. A snowboarder south of Teton Pass was caught, carried 800 feet and partially buried in a steep northeast facing avalanche path. Similar events are likely to be triggered by riders and skiers today. These slides are large with depths to one meter. Observers have reported widespread whumphing and collapses of the snowpack, which are indicative of unstable conditions. Avalanches are unlikely in areas below an elevation of 8,000 feet where the new snow that has fallen since last Sunday has accumulated on bare ground. Excellent terrain evaluation skills, a knowledge of the extent and distribution of persistent weak layers and conservative terrain choices are essential for safe travel in avalanche terrain.

( Discussion is generated from the previous day's afternoon forecast. )Temperature inversions may develop under a transient ridge. Skies are likely to be clear, however some areas of low-level status clouds and valley fog are possible. Skies will be mostly sunny in the morning with increasing clouds in the afternoon. Areas of light snowfall are possible Sunday evening. Temperatures are forecast to drop below zero overnight and rise into the 20s during the day. Winds will be light at 15 miles per hour with higher gusts and will back from the west to the south.Conditions will continue to be dangerous on steep slopes above an elevation of 8,500 feet. Large slab avalanches could be triggered by humans on persistent weak layers that formed on old snow surfaces during an extended dry period in November. Persistent weak layers are problematic because large slab avalanches can be triggered on them by the weight of a single person even though a slope has been previously crossed. These slides can also propagate long distances, be triggered from below, occur in treed areas and occur on slopes that rarely slide. These slides could be 2 to 4 feet deep. The general avalanche hazard is expected to considerable on all aspects above an elevation of 9,000 feet and on steep slopes that face north down to an elevation of 8,000 feet. Avalanches are unlikely below an elevation of 8,000 feet and on solar aspects up to an elevation of 9,000 feet. Excellent terrain evaluation skills, a knowledge of the extent and distribution of persistent weak layers and conservative terrain choices are essential for safe travel in avalanche terrain.