Avalanche forecast

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

While not likely, you may be able to trigger large avalanches on shadier slopes that face away from the afternoon sun. As you climb in elevation to areas where the wind frequently forms drifts or hardens the snow surface, the chance of triggering slides increases. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2

    Dense, 2-3 foot thick slabs overlie multiple weak layers (sugary facets, surface hoar, and crust + facet combinations) on many slopes, including sunnier aspects. The weak layers are worst and remain suspect on slopes facing the northern half of the compass (NW-N-NE-E).

    You may or may not observe any obvious signs of instability, such as cracking or collapsing, before triggering a slide. Avoiding steep terrain where the problem exists is the only surefire way to take Persistent Slab problems off the table, and, unfortunately, the only way to know if these lingering instabilities exist is to dig into the snow. Identifying safe-to-ride slopes on the northern half of the compass is not easy right now.

    Additional Discussion - Wind Slabs: Watch for dunes, waves, and textured surfaces to identify areas where the wind deposited snow in all exposed upper elevation and alpine terrain. Feel for stiff snow overlying weaker or softer snow; this snowpack setup can feel or sound "hollow" or "drummy". Smaller Wind Slab avalanches can trigger much larger Persistent Slab avalanches as they move downslope.

Avalanche Discussion

Avalanche problem distributions describe how common the problem is within a given chunk of the avalanche danger rose. We use a simple three-step scale to describe distribution: widespread, specific, and isolated. Widespread problems are expected to be found on most (or all) slopes. Specific problems exist in terrain with similar characteristics or patterns of presence—examples include wind-loaded alpine terrain or slopes >40 degrees facing the sun. Isolated problems are difficult to find patterns in terrain with and often considered “pockety” in nature.

Widespread problems, such as our current persistent slab structure, make it more probable to trigger avalanches in more locations. The upside of this distribution is that there is less uncertainty about where you’ll find the problem, which makes avoiding these areas more straightforward. In contrast, problems with isolated distributions are far more challenging to pinpoint and increase the opportunity for us to get unpleasantly surprised. Being that we’re stuck with widespread persistent weak layers buried 2-3 ft below the surface on northerly slopes, it’s worth sticking to the idea that if we can't prove beyond a shadow of a doubt that the avalanche problem doesn't exist on a particular slope, then we consider it guilty.

Join us at 6:30pm tonight at the Liberty Theater in Hailey for a presentation by Sawtooth Avalanche Forecasters Ethan Davis and Nick Zelaya. They will recount and reflect on an avalanche that caught both of them earlier this year while out on a field day in the Baker Creek drainage.

Regions covered