Turnagain Pass

The last known avalanche activity was small natural wind slabs triggered during the last outflow wind event 5 days ago.

Another round of NW outflow winds are impacting the forecast area today after a small refresh of 2″ of new snow overnight. This fresh snow combined with the soft surface snow that made it through the last round of winds this past weekend will be enough to create fresh wind slabs today up to 1′ deep. Wind slabs are most likely to form at upper elevations along ridgelines, cross loaded gullies, and convex terrain features. Human triggered avalanches will be possible today and natural avalanches unlikely.

We were pleasantly surprised yesterday that there was plenty of soft surface snow left over from the last round of outflow winds (ob here). It can be hard to tell just by looking at the snow surface where there are stiff wind slabs and where the snow surface is still soft. Stepping out of the skin track to feel the snow surface with your poles or feet is a great way to get a better sense of the surface conditions. Look for stiffer or hollow feeling snow at the surface to identify areas that have been wind loaded. Using small test slopes can be another good way to check whether fresh wind slabs are building up and if they are sensitive to human triggers in the area you want to ski or ride. As always, set yourself up for success by only exposing one member of your party to avalanche terrain at a time and spotting your partners.

Signs of recent wind transport on the snow surface from Tincan Common. The winds that created this texture occurred last weekend, but similar weather today will move the snow into fresh wind slabs at upper elevations. Photo 11.30.22

It has been over 2 weeks since the last known avalanches occurred on the layer of facets on the ground. However, we have not had a lot of snowfall to put stress on that weak layer in the past 2 weeks. At upper elevations (above 3000′) the snowpack remains thin in many areas and the facets on the ground appear to exist across the forecast area. It is tempting to disregard this weak layer since it has been so long since we have seen avalanches on it, but it is still possible to trigger a large avalanche on this layer at higher elevations. It is common for persistent weak layers like this to lay dormant for long periods and re-activate with the onset of significant new snowfall or rapid wind loading. Avalanches on this layer could be 1-3′ deep and would have high consequences if a person were involved.

Comparison of snowpack structure from upper elevations on Tincan. The weak layer exists in both locations but is better preserved and drier on the N aspect at higher elevation. Photo 11.30.22