Up to two feet of new snow has fallen in the Salt River and Snake River Ranges during the past 48 hours. Lesser amounts fell in the Wyoming Range. At the higher elevations (above 9,000 feet) this new snow and southwest to northwest winds have loaded a persistent weak layer of faceted snow that lies upon a hard rain crust that formed in October. Large slab avalanches were reported to have released naturally and by humans on this layer in the Teton Range yesterday. A conservative approach to suspect terrain and expert terrain evaluation skills are essential for safe travel in avalanche terrain today. Large avalanches are unlikely below an elevation of 9,000 feet where snow depths remain shallow and the October rain crust is absent at the base of the snowpack.
On northerly aspects at the upper elevations up to four feet of new snow lies upon a persistent weak layer of faceted snow and a hard crust near the base of the snowpack. Dangerous large slab avalanches could be human triggered or release naturally on that October rain crust in response to continued loading from today's gusty northwest winds.
( Discussion is generated from the previous day's afternoon forecast. )Although some snow shower activity and banding continues this phenomenon is on the decrease as a high pressure ridge begins to build in from the west and conditions become dryer. Skies are to remain cloudy overnight and on Tuesday with lingering snow showers. Temperatures will be in the single digits and teens at the higher elevations and in the teens and 20s in the valleys. Winds will be northwesterly at 20 to 25 with gusts to 35 miles per hour and will continue to load on leeward slopes.Dangerous conditions exist at the upper elevations. Poor route selection and/or terrain choices could prove fatal. In steep terrain that is underlain by the facets on rain crust problem layer, large to very large slab avalanches could be triggered by the weight of a single person or release naturally. Remote triggering is a reality and could occur as a result of human presence in an avalanche run out zone. Expert terrain assessment and travel skills are essential for safe travel in avalanche terrain. In isolated areas at the mid elevations this hazard extends down into steep north facing avalanche prone terrain. Storm snow instabilities are a potential concern at the mid and upper elevations in steep terrain where the facet/crust problem layer is absent. Avalanches are unlikely at the lower elevations where the snowpack is still quite shallow. The general avalanche hazard is expected to be CONSIDERABLE at the upper elevations, MODERATE at the mid elevations and LOW at the lower elevations.
