Turnagain Pass

Eddie’s: Skiers reported one natural avalanche triggered on Sunday by a refrigerator-sized chunk of cornice falling onto the slope, and another skier-triggered avalanche on a similar piece of terrain. They occurred on the steep south-facing terrain behind Eddie’s. Nobody was caught in either slide. Both avalanches were about 10” deep and around 50-100’ wide, failing on a layer of buried surface hoar. More details here.

Looking up at the start zone of one of the avalanches in the Eddie’s spines. Photo: Peter Ostroski. 02.21.2021

Winds are shifting back to the southeast as active weather moves in later today. With light to moderate westerly winds moving snow since yesterday afternoon, we can expect to see tender wind slabs on most aspects of the compass today. Fresh wind slabs may be up to a foot deep on some slopes, and they can potentially trigger larger avalanches on persistent weak layers buried deeper in the snowpack (see problem 2 below). Luckily, wind slabs are fairly easy to recognize. Avoid steep slopes with stiff or punchy snow on the surface. Shooting cracks or collapsing are additional clues that conditions are conducive to avalanches. A fresh wind slab may look like a smooth, rounded pillow of snow. The most common terrain features harboring fresh wind slabs will be just below ridgelines, the downslope side of convex rollovers, or in cross-loaded gullies. All of these terrain features will be suspect today, especially as winds pick up this afternoon.

We have been talking about two buried weak layers every day for over a week now, and they still continue to show that they are capable of producing avalanches. In the past week, we have seen avalanches failing on these weak layers in every elevation band. The most recent activity was on Sunday, with two avalanches that were large enough to bury a person failing on a layer of buried surface hoar near a ridgeline at 3400’. More activity will be possible today, and continued winds (see problem 1) are not improving the situation in the short term. We have been digging pits all over the advisory area to track these weak layers, and we have been able to find it on most aspects and elevations.

Because these persistent weak layers are present throughout the area, safe travel in avalanche terrain means recognizing the fact that most steep terrain in our area has the potential for avalanching. If you are trying to access steep terrain, consider the consequences of triggering an avalanche. Be careful with your choices- avoid steep terrain with terrain traps like cliffs, rocks, or trees below, or steep slopes that drain down into gullies or abrupt transitions where avalanche debris will pile up deeper. We need to be patient and avoid big and consequential terrain for now- there is still plenty of season left and these layers are trending in the right direction, but they haven’t gained enough strength to be trusted just yet.

Wind transport along the Magnum ridge. 02.22.2021

Crown line of an avalanche that failed on a layer of buried surface hoar in the Eddie’s spines on Sunday. Photo: Peter Ostroski. 02.21.2021