Turnagain Pass Avalanche Forecast

There were no known avalanches yesterday. The last avalanches were two days ago on Sunday and related to the strong NW winds. Two of those were on the south end of Seattle Ridge.

There are two main avalanche issues to deal with right now. The first is fairly easy to identity and are winds slabs from the past few days. The second, is not so easy, and related to the buried weak layers discussed in Problem #2.

Wind Slabs:  Although the NW winds got to much of the mountains on Sunday, it does appear that portions of Turnagain Pass were spared. Additionally, there was a bump in easterly wind yesterday that was able to move some snow around. This means we have to be on the lookout for the classic wind slab signs. Those are wind texture and signs of loading on the snow surface, cracking in the snow around you, and feeling for stiffer snow over softer snow.

Wind slabs in the Summit Lake area and other places that really saw the brunt of the NW winds could be quite stiff and large. They could be sitting on weak snow and not likely to heal very quickly. Any wind slab is likely overlying a weak snowpack in general and that is a double concern. With this setup, a smaller wind slab can release only to trigger a larger, much more dangerous, slab.

Looking east from the lower Eddies ridge- snow blowing off the ridgeline back toward Kickstep yesterday. 12.13.2021.

We are entering into a ‘scary MODERATE’ avalanche danger with respect to the buried weak layers we have talked about for a month now. This means those layers of facets and buried surface hoar are still there, we know it, but they are buried more deeply and are becoming harder to trigger. A scary MODERATE basically means we could start getting away with being on steeper slopes, but maybe not always, and if not, the consequences could be deadly. This is not a fun situation.

The weak layers are generally becoming one layer of faceted snow between 4-12″ thick depending on your location. They are anywhere from 3 to 5 feet deep, shallower in the Summit Lake area. The mid-elevations (1,500 to ~3,000′) have been the most reactive and this is likely because there is the old Halloween crust right under the facets. Open areas in the trees are also showing they are a concern. See the photo below from Seattle Ck drainage.

If you are choosing to start stepping into larger terrain, knowing that you could trigger a large slab is critical and slopes that have seen little to no traffic this season are more likely to avalanche. Watching your partners closely, only exposing one person at a time, and having an escape route planned are all ways to help hedge your bets. Also, thinking about the consequences if the slope does slide; will the debris pile up deeply in a terrain trap or spread out? It’s always better to avoid terrain traps.

If you’d like to just play it safe and avoid the issue all together, there is plenty of fun to be had on slopes less than 30 degrees with nothing steeper above you.

Photo highlighting potential for slabs in the lower terrain in/near the trees. Seattle Creek drainage – north end on the west side (east facing slope) just above Turnagain Arm. Natural avalanches from Thursday 12.9.21.