Avalanche forecast

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 7 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Triggering avalanches on deeply buried weak layers continues to be a possibility. Numerous very large and destructive avalanches failed naturally on these weak layers during the storm last week. Sticking to lower angled terrain and avoiding shallow areas in the snowpack are the best ways to reduce your risk. In upper elevation terrain, be on the lookout for thin, recently formed drifts of wind-blown snow that may be sensitive to the weight of a skier or rider.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3

    Persistent weak layers are buried near the ground in this zone. When I went looking for this weak snow on Saturday I found it, but it took some digging. On a mid-elevation, north-facing slope, snow from before Thanksgiving was buried underneath a dense, 6-foot thick slab of settled snow. Unfortunately, we don’t have good tools to help us forecast for these types of deeply buried weak layers. We can see that the snowpack structure isn’t great (picture a sturdy house built on a foundation of sand), but we can’t predict exactly when or where you might affect the weak snow underneath.

    When dealing with deeply buried weak layers, here are two good approaches for reducing your risk:

    1. Avoid likely trigger points. You’ll be most likely to impact these deep weak layers in areas where the snow cover is thin, like near rocky outcrops. Heavily wind affected areas where the wind has created a patchwork of scoured and loaded slopes are also more likely to be problematic.
    2. Keep an eye on the terrain you are traveling through and underneath. Avalanches are most likely on slopes between 35-45 degrees of steepness. However, persistent slab avalanches can be triggered remotely — from below or to the side of steeper slopes.

    ADDITIONAL DISCUSSIONYesterday’s storm brought 4-6” of new snow to this zone. Remote weather stations indicate that winds speeds have remained light through this storm and I expect any wind slabs that you might encounter today will be isolated to exposed, upper elevation terrain. These slabs are likely to be more touchy where they are sitting on icy crusts or slick, alpine surfaces.

Avalanche Discussion

I like to think about the snowpack as a record of a season’s worth of weather, written in snow and ice. Thinking about it this way helps me to understand it as a dynamic animal, instead of a static, unchanging object.

Because of this, the snowpack is a different animal every year. Some years are marked by generally good stability and relatively easy to assess and manage avalanche problems. Other years have us traveling through the mountains with the hairs on the backs of our necks raised. If you’ve been out and about this season, you know that we’ve found ourselves in the later category. The depth of the snowpack varies considerably across our region, but we have a variety of persistent weak layers of snow across the board. 

In our northern areas, where the snowpack is deeper, triggering an avalanche involving this weak snow is less likely, thanks to the thick slab of snow on top of it. Picture a well-armored, sleeping dragon — you can walk in a lot of places without waking up the beast, but if you find the chink in her scales (thin trigger point), you find yourself facing an unsurvivable problem.

In our southern areas, where the snowpack is thinner, we are dealing with the flip side of this equation. Avalanches here will be smaller, thanks to the thinner slab that would be involved. But, you’re more likely to find a trigger point because the weak layers are closer to the surface. And notice that I said “smaller”, not small. The consequences of triggering one of these slides can be high, particularly in areas where you would be carried through trees or swept into an abrupt terrain trap where avalanche debris can pile up more deeply.

Regions covered