Avalanche forecast

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Weak layers buried underneath dense, 2-4 foot thick slabs can produce large, destructive avalanches.  You aren't likely to experience signs of instability with these deeper weak layers—the first sign may be the large avalanche you trigger. It is possible to trigger small slides on wind-affected snow in upper elevations.  Choose simple terrain free of terrain traps to reduce your risk.

Avalanche problems

  • Persistent Slabs

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

    What is it? A very dense, 2-4+ foot thick slab stands over buried weak layers of facets or crust + facet combinations. While these avalanches are getting harder to trigger, releasing these destructive beasts is not impossible. Watch the video to the right/above to understand this problem better.

    Where is it? Most slopes harbor these layers. You'll find crust + facet combinations on sunny slopes and small facets on shaded slopes. We are still tallying up the historical amount of slides produced by these weak layers (map, list). 

    How can you recognize it? The first sign of instability may be the large, destructive avalanche you trigger. Tracks on a slope don't indicate it is good to go. These slides may break much wider and further above you on the slope than expected. Unless you dig down to confirm the weak layer exists, you might assume the snowpack feels good under your feet or sled. And if you take the time to dig down, don't trust the results of your stability tests. They serve little help when dealing with such a dense slab overlying this weak layer. 

    How can you manage it? The only way to eliminate your risk of encountering one of these devastating slides is to avoid avalanche terrain and terrain exposed to hazard from above. I know that's not satisfying to hear. You can reduce your risk by avoiding slopes steeper than about 35 degrees—especially large avalanche paths and those with ugly consequences if caught in a slide. Remember that even small slopes can have high consequences when dealing with very dense slabs. These slides can be triggered remotely—from gentler terrain above, below, and to the sides of steep slopes.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    What is it? Yesterday, professionals in Galena Summit reported some natural activity on northern-facing slopes in the mountains south of this Zone. It is possible to trigger similar slabs in the upper elevations.  Some slabs may be sitting over sugary, faceted snow, which can be more sensitive than your typical wind slab problem. 

    Where is it? You'll likely find slabs in upper-elevation terrain, near ridgelines, and mid-slope terrain features like ribs, chutes, and couloirs. The rocky nature of the Sawtooth mountains allows new snow to run down the sides of cliffs and form slabs in the aprons below these features.

    How can you recognize it? Look for shooting cracks exiting from your sled or skis or collapsing in the snowpack. These are signs of unstable snow. You can recognize wind-affected areas by stiffer or harder snow that supports your skis or machine and surface texture such as ripples, waves, or dunes. It may sound hollow or drumlike. 

    How can you manage it? Steer away from avalanche terrain when encountering slopes with denser snow or signs of instability.  Smaller triggered slides can be effective triggers for the weak layers described in the Persistent Slab problem above.

    ADDITIONAL DISCUSSION: Small loose snow avalanches can occur on very steep, sheltered, and shady slopes. These slides can knock you off your feet and carry you through cliffs, trees, gullies, or other terrain traps. These smaller avalanches can be effective triggers for the large persistent slabs described above. 

Avalanche Discussion

The Avalanche Danger has decreased to MODERATE, but you can still go out and trigger the same catastrophic avalanches as in previous days. The underlying persistent slab problem continues to drive my terrain selection to be in simple terrain free of terrain traps and large features. It should only take a visit to one of the massive debris piles (refer to the Avalanche Database) that took out trees and barreled down through large avalanche paths to remind you of the consequences of triggering one of these sleeping giants. 

Be on the lookout for different generations of wind-loaded slopes in the alpine. These slabs are more problematic on the shady slopes after the sun likely cooked down any fresh snow yesterday. Moderate southerly winds will make easy work of moving new snow into thin, small slabs today.  If the snow pounds down faster and more than expected, be aware of growing slabs. Triggering these small slabs can add more weight to the snowpack as they move downslope. They can serve as fresh triggers to wake up the weak layers buried deeper in the snowpack. Move away from wind-affected slopes in avalanche terrain, where the snow is becoming deeper and denser.

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