Recent and wind-drifted snow has added additional stress to buried persistent weak layers increasing the likelihood of human-triggered avalanches in some locations. The danger is greatest on steep, wind-loaded, northerly aspects near treeline and above.

A layer of near-surface facets (NSF) formed during the long December dry spell. This layer is now buried about a foot deep and has been sensitive in recent stability tests. It is especially reactive in areas where the wind has drifted enough snow to form a stiff slab on top. Strong winds over the past few days have made this problem more widespread. Human-triggered avalanches are most likely to fail here first and could be 1-3 feet deep in drifted areas. It is important to carefully analyze any slope you are considering by digging down to see if the poor structure exists. Avalanches triggered on this weak layer could also step down into our second faceted weak layer at the base of the snowpack. Avalanches failing on this layer would be deep, dangerous, and possibly un-survivable.

The overall height of snow is still relatively shallow, and the faceted snow at the base of the pack will remain a concern until we get a much deeper snowpack. While the chances are low, full-depth hard slab avalanches failing on the basal facets remain possible in thin snowpack areas or steep, rocky, radical terrain. To avoid this problem, we are simply avoiding big lines in alpine terrain.

In the video below, Dave Garcia demonstrates the reactive potential in our primary layer of concern.

Strong winds blowing from the north over the past couple of days have whipped up a fresh slabs of wind-drifted snow. Look for unstable slabs on all aspects above treeline. This problem is most pronounced in the alpine, but I wouldn't be too surprised if some drifts penetrated into near treeline terrain as well. The recent drifts will be especially sensitive anywhere they have formed above the preserved NSF layer that was buried on 12-25.