Silver Valley & Bitterroot Mountains

Slabs that have denser snow resting on weak snow are quickly consolidating under the presence of warm temperatures, creating dangerous conditions. The increased warmth will also create wet snow problems, and the line where these hazards change is likely to be blurry and complex. With a complicated array of conditions, opt for lower angle terrain that does not have steep overhead hazards, especially if you see cracking on the surface ahead of your skis or boards.

Today is one of those days where avalanche problems don’t fit so cleanly into one box or another. There are a couple of factors at play, but today’s hazards will largely be centered around the weather, and we all know how fickle that can be. 

The last storm cycle that started on Wednesday evening was short but effective, leaving many of the ranges across the forecast area with around 8 inches of new snow. The Selkirk Mountains look to be the standout winner, with the Schweitzer SNOTEL site reading just over a foot of snow. Snowfall initially started lower density, laying down a layer of weaker snow before denser snow built above that. This alone has created an inverted slab, and warmer temperatures today will increase the rate of slab consolidation.

But it’s not just the inverted slab alone that’s a cause for concern; the interface below the snow is worrisome as well. A brittle and thin crust sits between the snow that fell right at the end of March and the most recent snow. This has added some complexity to the upper snowpack, and field teams in the Selkirk Mountains yesterday found that this interface was a common place where snow wanted to fail on. Not far below the brittle crust sits a much thicker and firmer crust, acting as a slick planar surface. Because of how robust the lower crust is, current hazards are confined to the snow above it, but the upper snowpack has enough depth to produce large and dangerous avalanches.

Slabs will be even larger and denser where previously strong to extreme winds have increased overall slab depths. Swirling winds in the previous 24 hours got to work and relocated snow onto some more atypical aspects. Around ridgelines, steep mid-slope terrain features, and more open and exposed slopes are likely to harbor deeper drifts. The presence of the concerning thick and slick crust means that avalanches could propagate wide distances across the slope, and run a long way as they quickly move downhill.

Now for the real wild card: the sun. Cloud cover (or the lack of it) will heavily dictate where, and when, wet snow problems emerge. If the potent spring sun shines longer than expected, loose wet avalanches will unfold rather quickly. If the mid and high-level clouds effectively block some of the solar radiation, that could hamper the development of the surface snow softening. Moving in the mountains today should be centered around diligently reading your environment and looking for evidence of small changes.

Oftentimes, it’s a satisfying feeling to have the avalanche problems and their distribution fit neatly into aspect and elevation ranges. Occasionally, it’s a pretty straightforward layout, and other times, you have overlapping problems to manage on the same slope, with very different avalanche hazards existing at the same time. Today is the latter. Expect dynamic conditions with various aspects and elevations. The best way to manage all of this uncertainty? Lean on terrain choices by sticking to low-angle slopes.

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