Turnagain Pass

The last reported avalanches in our forecast area were immediately following the 12/14-15 storm event. There were multiple very large avalanches that appear to have failed on the facets near the Thanksgiving crust, with the biggest activity in the Girdwood Valley and on the south end of Turnagain Pass.

With another day of quiet weather on the way today, our main avalanche concern is the potential for a person to trigger a persistent slab avalanche 2-4′ deep on weak, faceted snow surrounding a crust that formed back before Thanksgiving. Without a significant load in the past 5 days this layer is becoming more stubborn to trigger, but it still cannot be trusted. It seems the most concerning zones within our forecast area are the mountains around Girdwood and towards the south end of Turnagain Pass. From the observations we have received over the past week, there is also cause for concern outside of our forecast area in Chugach State Park and in the Summit Lake area.

This is a tough problem to manage. These deeper persistent weak layers do not always give clear warning signs of instability even though there is still a very real possibility that a person can trigger a large avalanche. On the one hand we are still getting concerning test results in our pits (details here), but on the other there are tracks in steep terrain all over the pass. The problem with these stubborn persistent weak layers is that they can give you this mixed feedback even though they are still dangerous. These avalanches have a tendency to release after there are multiple sets of tracks on a slope. They can also be triggered remotely from below, above, or next to steeper terrain. At this point, the weak layer is stubborn, but not unreactive. Before moving into or below steep terrain, think about whether the terrain you’re considering matches the current snowpack. Is there an escape route if the slope does release, or are you traveling on a big, connected slope? If you are getting into steep terrain, does it have a planar runout, or are there terrain traps like gullies, cliffs, or trees below you that increase the consequences if you do get caught in a slide? Unfortunately these layers take a long time to heal, so it is looking like we are going to be dealing with this for some time to come. The good news is that you can avoid the problem entirely by sticking to slopes that are less than 35 degrees.

Dry Loose Avalanches: There is plenty of loose, dry snow on the surface that will be ready to sluff in steep terrain. While these avalanches are unlikely to be big enough to bury a person, they can still be dangerous if they catch you in consequential terrain. Pay attention to sluffing on steep slopes, and work across the fall line to avoid getting caught by surprise.

 This is the setup that is giving us cause for concern- a thick slab sitting on top of multiple weak layers of facets. This photo is from Cornbiscuit, but the poor structure is consistent throughout the advisory area and beyond. It seems the weakest zones are near Girdwood and towards the south end of Turnagain Pass. 12.18.2022

This very large avalanche in the Summit Lake area illustrates the problem at hand. This was a natural avalanche that likely occurred late last week, but it is still possible to trigger something like this today. Photo: Paul Wunnicke. 12.19.2022