There is weak, sugary faceted snow (a persistent weak layer, or PWL) on almost all aspects and elevations throughout the Wasatch Range. This PWL has been buried by several feet of storm snow and wind-drifted snow which has created dangerous avalanche conditions. This persistent weak layer is still dangerous on aspects facing northwest through north and east where triggering avalanches is less likely than it was yesterday. I would be stepping out into MODERATE terrain with optimistic caution and making sure I had all my bases covered, avoid stepping out in really high consequence terrain, have a partner and a plan in case the slope I was skiing on avalanched.

Spatial variability is key to avalanches and stability right now. What this means is that Upper Little Cottonwood, the Park City Ridgeline, and Mill Creek all have slightly different snowpack structure, stability, and energy. I would want to know exactly how deep this persistent weak layer is before jumping into steep northerly facing terrain. The structure (overall layering of the snow) is still poor with weak fist hard facets under the new snow although test results are showing that this is healing in some places. The upper Cottonwood Canyons, Park City Ridgeline, and Mill Creek all have different snowpack structures and heights.

Although avalanches involving this PWL are less likely on solar aspects facing west through south, there is uncertainty with wind loading and avalanches failing in this PWL are still possible.

On Saturday December 17 there was a skier triggered avalanche on the south face of Lone Peak. This slide was 150' wide and 8"-12" deep. I would expect to see similar wind drifted avalanches in isolated areas.

Photo (G. Gavin)