Abundant snowfall, combined with strong westerly ridgetop winds, has created dangerous avalanche conditions. Strong westerly ridgetop winds will continue to redistribute snow onto leeward slopes, adding depth and volume to wind slabs, as well as increase the load on persistent weak layers deep within the snowpack. Yesterday, several wind slabs were triggered in the Tetons. A larger slide released on the South Face of Taylor that reached the Coal Creek drainage. Similar avalanches are likely to be triggered today, and natural activity is possible. Any sustained periods of sunshine will make these slides more susceptible to failure. This scenario demands respect at the mid and upper elevations, and a conservative approach should be used for travel and terrain choices. With above-freezing temperatures at the lower elevations, backcountry travelers still have the potential to trigger pockets of shallow slab in steep, wind-loaded terrain.
Strong west to northwest winds have formed wind slabs on leeward slopes at all elevations. These slabs could be triggered with depths of two to three feet at the mid elevations and up to 18 inches at the lower elevations. Natural releases are possible, particularly near high peaks and ridge crests where the most significant loading has occurred, and where cornices may drop onto a slope.
Weak layers of faceted snow persist deep within the snowpack. Failure of these layers will produce very large avalanches with depths up to six feet. They could be triggered directly by backcountry travelers, step down from surface slabs, or release naturally. The consequences of being caught could most likely be fatal.
Snowfall is expected to return to the area after midnight and continue into Tuesday. Accumulations of five to ten inches are possible by the evening. Overnight lows in the mountains will be in the mid to upper teens before rising into the mid 20s during the day. Valley temperatures will dip into the mid 20s tonight before rising to near 40 in the afternoon. Westerly to northwesterly ridgetop winds will range from 20 to 30 miles per hour.The general avalanche hazard is expected to be CONSIDERABLE on Tuesday. In exposed terrain, backcountry travelers could trigger these slabs to depths up to 30 inches deep on steep, wind-loaded slopes. These slabs could step down to deep, persistent weak layers of faceted snow producing very dangerous slides up to six feet deep. Shallow pockets of new wind slab will slowly build as the day progresses. At the lower elevations, skiers and riders could trigger pockets of slab up to a foot deep in steep terrain if temperatures remain above freezing overnight, particularly if rain occurs during the day.
