Turnagain Pass

We saw small avalanches on short but steep wind-loaded features yesterday on Eddie’s. These were 6-18″ deep and around 50′ wide, failing on the layer of surface hoar that was buried five days earlier. The size of the terrain kept the avalanches small enough that they wouldn’t have buried a person. More details here.

Small avalanche I triggered with a ski cut on a test slope. 6-18″ deep, 50′ wide. The slope was previously wind loaded and the avalanche failed on a layer of buried surface hoar. 01.15.2023

We are dealing with two very different problems right now. The first and more likely problem to encounter is fresh wind slabs around a foot deep that have formed in the past 12 hours with strong easterly winds. These would be reactive enough on their own, but are made worse by the fact that they are loading a layer of surface hoar that was buried last week and was still reactive yesterday (details here). The second problem is a deep weak layer that is capable of producing massive avalanches, which will have higher consequences but will be more difficult to trigger (see problem 2 below).

Winds have been blowing out of the east at 15-30 mph since just after sunset yesterday, and although they should back off slightly during the day today, the slabs that have just formed will still be reactive. The most reactive slabs will be found at higher elevations, but you should anticipate some pockets of unstable snow reaching down into the middle elevation bands as well. Keep an eye out for recently loaded terrain features near ridgelines, on convex rolls, and in cross-loaded gullies. Fresh wind slabs will feel a bit stiffer, and may give you warning signs like cracks shooting out from your snowmachine or ski tips. Take the time to step off the skin track or hop off your snowmachine to see how the surface feels. Avoid steep slopes with stiff, wind-loaded slabs of snow on the surface. Remember, these avalanches near the surface may be the most likely problem to encounter, but there is potential for bigger avalanches failing deeper in the snowpack. Read on to problem 2 for more.

Fresh wind slabs that formed in the past 24 hours will be loading slopes that were already reactive, producing avalanches yesterday. This makes human-triggered avalanches likely today. 01.15.2023

It was hard to decide which avalanche problem got the number one spot in today’s advisory. Should it be the shallow, but more likely wind slab? Or should it be the less likely deep slab– difficult to trigger, but capable of producing avalanches big enough to take out large sections of forest or destroy a house? However you organize the avalanche problems, there is no question that the current snowpack is dangerous, and the way to manage it is by cautious terrain use.

It has now been 9 days since the last known avalanche on the Thanksgiving crust/facet combo that is buried anywhere from 3-6′ deep on average, but it is still a concern. Over the past week, we’ve been finding the same structure in our snowpits that produced the last avalanches on this layer. The most likely places to trigger an avalanche on this layer will be on slopes with a thinner snowpack. This is true as you consider the forecast area in general (generally thinner snowpack from the southern half of Turnagain Pass down to Summit Lake), or across specific slopes (thin spots on previously scoured terrain features where rocks may or may not be visible). There is a lot of uncertainty with deep slab avalanches, and the only way to truly manage your risk exposure with a problem like this is by stepping back from steep terrain.

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