Turnagain Pass

There were no known avalanches triggered yesterday. During a very brief clearing period yesterday we saw part of an avalanche crown that likely released earlier this week at about 3400′ in Todd’s Bowl on the N aspect of Tincan. The avalanche released mid slope about 200′ down from the ridge and looked to be about 1-3′ deep but did not appear to have very wide propagation. This avalanches looked very similar to some other recent wind slabs and storm slabs that released during or just after the last significant wind and snowfall event on Sunday and Monday.

Today should be a beautiful day to be in the mountains, with light snow on the surface, mostly sunny skies, and light winds. Winds are expected to be 5-15 mph out of the NW, which might be enough to form some small fresh wind slabs up to 1′ deep at upper elevations due to the very low density snow on the surface right now. These fresh wind slabs could be touchy if they are actively forming, so keep an eye out for snow transport along ridgelines and signs of recent wind transport on the snow surface. There is a chance of finding a larger wind slab 1-2′ deep lingering at upper elevations in steep terrain from the snowfall and strong winds earlier this week.

At lower elevations we have seen some evidence that the new snow from this week is not bonding very well to a melt freeze crust that formed on 1/25 and exists up to about 1500-2000′. For now the snow on top of this weak layer is pretty low density and doesn’t seem to be causing any avalanche activity, but it could become more of a concern with additional snowfall and wind on the way tomorrow and into the weekend. In general the snowpack seems to be adjusting well to the new snow load from earlier this week and avalanche conditions are much less reactive than what we saw during and immediately after that last loading event.

Cornices are getting quite large now and the potential exists for accidently breaking off a large piece and taking a ride down a steep slope. Give these a wide birth along ridgelines and be aware that they are more likely to fail when getting direct sun. Loose snow avalanches (aka sluffs) are also likely in steep terrain with low density dry snow on the surface. Be aware of where your sluff if building up and try to avoid being pushed into unsavory terrain.

Keep in mind that there is a layer of buried surface hoar about 2-4′ deep from 1/10 that exists across the forecast area but has been showing signs of becoming less likely to produce avalanches. We found this layer in all three of our snow pits yesterday on Eddies, but did not have any significant results on this layer in our stability tests. It is an encouraging sign that this layer is becoming much less reactive, but it is still feasible that this weak layer could be preserved in isolated sheltered areas or where the weak layer is more developed and could still cause large avalanches. It is worth taking some time to dig down and check for this layer in the snowpack before committing to larger terrain features. If you see large upright surface hoar grains in the snowpack or have reactive stability tests, like a compression test or extended column test, then it a sign that the weak layer could be more active in your area.

We have lingering concerns about the potential for very large avalanches on the Thanksgiving facet/crust combo towards the base of the snowpack. In Turnagain Pass, where the snowpack is generally thicker, we think this layer is unreactive and in a dormant phase. This weak layer is most concerning in areas with a shallower overall snowpack depth, like near Silvertip and the southern end of the forecast zone in general. An unexpected avalanche on a buried weak layer is more likely in these areas with an overall weaker snowpack structure.