Strong wind will drifted the new snow falling this morning into the lee of terrain features at middle and upper elevations. Small, human-triggered avalanches are possible in steep wind loaded terrain and may become unmanageable if the slab steps down into more deeply buried weak layers. The weak layer of snow buried in early December is the main driver of today’s avalanche danger rating. This weak layer has produced very large, and in some cases, remotely triggered avalanches. Considerable avalanche danger exists today above 8,500' due to the potential size of these avalanches. Careful snowpack evaluation and cautious route-finding will be essential today to identify and avoid areas where these avalanche problems exist. Avalanches are unlikely at lower elevations due to a much shallower snowpack, however don’t discount the possibility of triggering an isolated pocket in steep terrain.
The buried layer of faceted snow remains a concern. Slabs triggered on this layer could be two to four feet thick and break widely across the terrain. These slabs will be sensitive to human triggers and avalanches have been triggered from a distance. The increased load from new wind slabs or from multiple people or machines on a slope may trigger a very large avalanche.
Wind slabs may be up to eighteen inches thick and sensitive to triggering. Look for drifted snow below ridges and beneath and beside steep terrain features. One to three inches of new snow during the day may add to this problem.
( Discussion is generated from the previous day's afternoon forecast. )Active winter weather returns overnight with five to seven inches of new snow forecast for the mountains by morning and another inch or three tomorrow. Southwest flow will again favor the Tetons and the Salt River Range with the most snowfall. Ridgetop wind speeds are forecast to be forty to fifty miles per hour with gusts to seventy-five.New snow will add another three quarters in an inch of water weight to an already dangerous persistent slab problem. Wind loading of lee slopes will add further stress to the weak layer deep in the snowpack as well as building a slab on any near surface facets that have developed during the recent sub-zero temperatures. The combination of sensitive wind slabs and further loading of the deeper, persistent weak layer will keep the avalanche danger elevated tomorrow. You can expect fresh wind slabs one to two feet .. I think just to one foot and can change in am if it really snows… thick by morning plus the lingering concern of triggering a very large avalanche on the deeply buried facets. Avalanches with a destructive size of two and three (out of five) have been triggered remotely on this layer. Tomorrow, all forecast areas will very likely have a Considerable danger rating. Elevations below 8,000' which still lack much snow, continue to have a Low danger rating.
