Turnagain Pass

The only avalanche activity yesterday we saw or know of were many small to medium sized wet loose avalanches on steep southerly aspects. Some of these were able to pull out small slabs of snow around a foot deep or so.

It was an impressive springlike day for January. Temperatures were near 32F along the ridgetops. The steep southerly facing slopes heated up enough to dampen the surface snow to the point where natural wet loose avalanches were occurring. These aspects are likely to be sporting a bit of a crust now. However, even with the warm up and some wet loose avalanches, we did not see or hear of any slabs breaking in the buried surface hoar 2-3′ deep. Good news. For today, ridgetop southeast winds could blow just enough in some areas to form shallow wind slabs. Watching for active wind loading will be good if traveling along ridges.

The main concern however is triggering a 2-3′ deep slab on that layer of surface hoar that was buried on Jan 10th. The chances for triggering one of these slabs is much less likely than it was a week ago, when folks were popping these off left and right. As many know, a surface crust exists up to 2,000′ (ish). This can help to stabilize the pack in the lower half of the mountains, but the upper half is still a concern. These slabs can be triggered after tracks are on a slope and we are not likely to see any signs of instability to help warn us. This creates a tricky situation, one that we have had to deal a lot with this season.

As the days go by we are finding variable results in our pit tests, and folks are beginning to push into the steeper terrain without incident. We have transitioned into a lower likelihood, but still high consequence situation. If choosing to get onto the steeper terrain above 2,000′, especially the shady (no surface crusts) terrain, remember this layer is lurking. Having all our safety nets out is key. That means exposing one person at a time, have escape routes planned, make sure your partners are watching and they know how to use their rescue gear if the slope slides. Also, remember these slabs have the potential to propagate quite wide, making them large and unmanageable.

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Believe it or not, our friends to the south have been dealing with a very similar snowpack. They just posted this great article describing the difficulty with problematic buried weak layers. Check it out! Deep Persistent Slab Management and Mindset.

At the base of the snowpack are those old facets around the Thanksgiving crust. These are buried between 4-8′ deep across the forecast zone. Although it’s been three weeks since the last known avalanche on these layers (Cornbiscuit on 1/7), we are still keeping them on our radar. It’s unlikely a person will trigger this deep layer, but an outlier avalanche could happen if a person hits just the right (or wrong) thin spot or an avalanche in the layers above steps down and triggers a larger slab. Moving forward this problem is heading to a dormant phase, which means it may not react until it gets a new load of snow. This is a typical pattern for these Deep Persistent Slab avalanche problems.

Gotta love Turnagain Pass on these sunny days. However, those southerly slopes were baking yesterday. Clouds today with cooler temps should keep those sun crusts from softening. 1.28.23.