Avalanche forecast

Banner Summit

Sawtooth Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

An intense winter storm bringing 8-10 inches of snow and strong wind will overload a very weak snowpack. Very dangerous avalanche conditions are expected to develop by tomorrow. Fresh deposits of wind-blown snow will be very reactive to your weight. You will be able to trigger slides that could involve the entire snowpack from flat terrain a long distance from the slope. 

The backcountry avalanche watch does not apply to the HWY 21 avalanche program.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–2

    8-10 inches of new snow will fall before 5pm today with strong winds. Winds will build very touchy slabs on all aspects at both middle and upper elevations.  You'll find large, reactive wind slabs on many slopes today, thanks to the amount of new snow and the strength of the wind. Look for signs that the wind has been at work such as ripples on the snow surface, dune-like drifts, and fresh cornices. If the snow you are moving through suddenly becomes deeper and denser, you've likely found a fresh slab. Cracks shooting out from your skis or machine are a clear sign the slab is unstable. Look for slabs near ridgelines and adjacent to mid-slope terrain features like ribs and gullies. In more sheltered terrain, expect to be able to trigger slides in softer, new snow. 

    Avalanches failing within the new snow will be effective triggers for deeper weak layers.

  • Persistent Slabs

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

    A layer of weak snow near the ground exists on many slopes. Today's windy and wild storm is pushing this weak snow towards its breaking point.  By the end of the day, triggering a destructive slide on this layer will become likely.  Avalanches that break on this layer could fail 2-4 feet deep, involving the entire snowpack. These will be large enough to not only take you out, but also could be large enough to bury your car. The likelihood of triggering one of these slides will increase dramatically throughout the day.

    Avalanches can be triggered from flat terrain a long distance from the slope.  Pay close attention to the terrain you are traveling through, but also to slopes you or others are traveling under. These slides will run longer than seen yet this season. 

Avalanche Discussion

A large storm pulse will bring 8-10 inches of snow and strong winds to overload a very weak snowpack. Very dangerous avalanche conditions are expected to develop by tomorrow. Fresh deposits of wind-blown snow will be very reactive to your weight. If you decide to head into the mountains today, be aware that avalanches can be triggered from flat terrain a long distance from the slope. This is the first large loading event our very weak underlying snowpack has seen this season.  Today is the day to expect the unexpected when it comes to slides — large paths can rip and run unexpected lengths. 

The backcountry avalanche watch does not apply to the HWY 21 avalanche program.

Regions covered