Turnagain Pass

A snowmachine triggered a 3′ deep slab in the Placer Valley around 2,500′ in elevation (Squirrel Flats area). They were able to ride away without getting caught or carried. We also noticed multiple natural avalanches in the mid and upper elevations along the Seward  Highway from the Placer Valley through Summit Pass.

This avalanche was triggered by a snowmachine yesterday in the Squirrel Flats area above the Placer Valley. Photo: Jonathan Tymick, 02.14.2024.

The relentless wind storm we’ve been experiencing this week is expected to continue today, which means we are still expecting to find dangerous avalanche conditions. The current setup is much more complicated than a typical wind slab problem, because of the strength and duration of this wind storm, the dangerous weak layer buried below the surface, and the unusually warm temperatures we are experiencing. We’ll dig into the details below, but the important thing to keep in mind is that we are looking at a really challenging and potentially dangerous snowpack right now so the best way to stay out of trouble is to avoid travelling in steep terrain until the snowpack settles down.

Today will be the fourth consecutive day of sustained 20 to 50 mph easterly winds. At some point we are going to run out of soft snow for the wind to move into fresh slabs, but based on the massive amounts of snow we saw blowing off ridgetops yesterday we are still expecting to find reactive wind slabs forming today. The wind slabs forming with winds this strong will likely be very stiff, which may make it possible to get way out onto a slope before triggering an avalanche. We are also seeing strong winds dipping down into our treeline elevation band so be on the lookout for wind slabs in unusual places today. This loading event is adding stress to a dangerous weak layer, and that combination of a fresh wind slab on top of a weak snowpack was responsible for the fatal avalanche accident in Summit Pass on Tuesday. This avalanche problem is not straightforward. The best way to manage it for now is to keep a conservative mindset and stick to lower angle terrain.

Wet Snow Avalanches will also be possible with another day of unusually warm temperatures. This is the time of year when we notice the sun starting to effect snow surfaces on solar aspects again, and that increased solar input combined with the current heat wave will increase the chances of loose wet avalanches. It may also increase the likelihood of triggering a bigger avalanche on weak snow buried in the upper snowpack (more in problem 2).

Cornice Fall: This wind event has made some very large overhanging cornices. The combination of strong winds, warm temperatures, and a lot of solar warming will increase the likelihood of natural cornice failures. Be sure to limit time spent traveling under them.

These natural avalanches on the east side of Wolverine above the Placer Valley are an example of the complex problem we’re still expecting to see today. They were probably triggered by heavy wind loading, but look to have failed on persistent weak layers deeper in the snowpack. 02.14.2024

The weak layer of faceted snow that formed in January is still a major concern for today. This was the culprit in the avalanche accident in Summit Pass on Tuesday, and we have seen it throughout our advisory area. The distribution of the layer is tricky to identify. The snow is probably weakest in sheltered terrain between roughly 1000′ to 2000′, but it is experiencing the most stress at and above 2000′ as the strong easterly winds continue to load the snowpack. The problem layer can be tricky to identify with any of our quick travel tests like hand pits or test slopes, so if you really want to assess the problem you’re going to have to take the time to dig a snowpit. Based on the potential size and consequences of these bigger avalanches, it may be a better idea to just simplify your terrain choices and stick to mellow slopes until this problem heals.

This layer of faceted snow was the layer responsible for the avalanche accident in the Summit Pass area on Tuesday, and it exists throughout the advisory area. 02.14.2024

The widespread glide activity is still on our radar, and we’re not sure how this warm spell is going to impact the problem. As always, avoid travelling under slopes with open glide cracks since they release unexpectedly. Some glide cracks are harder to identify since they were buried by last week’s snow, so look carefully and be aware of the potential for falling into a crack that is bridged over by a thin layer of snow.