Heavy snowfall and increasing winds will create dangerous conditions as the hazard rapidly increases to considerable at the mid and upper elevations and moderate at the lower elevations. New soft slabs are likely to be sensitive to human triggers. Natural releases are possible. In areas with poor snow structure large slab avalanches could fail on buried persistent weak layers and step down through old snow layers. Expert snowpack evaluation and route selection skills are essential for safe travel in avalanche terrain.
Southwest winds will be forming new soft slabs on leeward aspects and at the higher elevations cross-loading steep avalanche prone terrain features. These slabs will be forming on good sliding surfaces and are likely to be easily triggered by humans. They could release naturally with depths to two feet at the higher elevations and in pockets with depths to a foot at the lower elevations.
Persistent weak layers in the snowpack are being loaded. These layers may collapse and cause large slab avalanches that will be comprised of the new storm snow and older snow. These slabs could be 2 to 4 feet deep at the mid and upper elevations and up to two feet deep at the lower elevations. They could be triggered by the weight of a single person. Natural releases on these faceted problem layers are possible.
The Winter Storm Warning will continue overnight through 11 AM on Friday. Light to moderate snowfall will continue overnight before decreasing in intensity on Friday. Overnight lows in the mountains will be in the mid-teens before rising to near 20 during the day. Ridgetop winds will veer to the west at 15 to 25 miles per hour.The general avalanche hazard is expected to remain Considerable on Friday. In steep, wind loaded terrain above 7,500 feet, skiers and riders could easily trigger newly formed wind slabs one to two feet in depth. Loose snow sluffs will be possible in terrain less affected by the wind. Continued snowfall will further load persistent weak layers of faceted snow deeper in the snowpack. These slabs, with depths of two to four feet, could be triggered directly by backcountry travelers or indirectly by stepping down from the release of a wind slab. Natural activity will also be possible. Below 7,500 feet, skiers and riders could trigger slab avalanches one to two feet in depth. Expert snowpack evaluation and route selection skills will be essential for safe travel in avalanche terrain.
