Bulletin d’avalanche

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Danger d’avalanche

Sat
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Very dangerous avalanche conditions exist. Large human-triggered avalanches are very likely in windy, alpine terrain. Expect naturally occurring loose snow avalanches to release on very steep slopes that directly face the sun. A much larger avalanche failing on weak layers deep in the snowpack could be triggered without warning. These massive slides will be large enough to snap trees.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    2

    This zone picked up 15-20" of snow since Wednesday evening, accompanied by moderate SW and W wind. Storm snow likely did not bond well where it landed on facets, crust + facets, slick crusts, and surface hoar. Expect to encounter a host of new snow problems. These range from 1-2' thick sensitive wind slabs at upper elevations to potentially touchy slabs and loose snow sluffs that fail readily in steep, sheltered terrain. Look for obvious signs of instability, like small recent avalanches or cracking and collapsing of the snowpack. Even smaller slides in sheltered terrain can have big consequences if they push you into terrain traps like stands of trees or a creek bed. Importantly, any smaller natural or triggered avalanche has the potential to step down to a deeper weak layer, releasing one of the Persistent Slab avalanches described below. ADDITIONAL DISCUSSION: This afternoon will be clear, sunny, and mostly calm. Expect naturally occurring loose snow avalanches on slopes that face the sun. The Sawtooths' large, rocky, steep slopes are the ideal terrain for these slides. Starting at a point, these slides will gain mass as they move downhill, running fast and far on slick crusts. Rollerballs or pinwheels are a clue that the snow surface is weakening, and loose snow avalanche activity may follow. 

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3

    You could trigger large avalanches, and some of them could be big enough to destroy houses. Multiple natural and human-triggered avalanches released in the southeastern portion of the zone during and shortly after storms in early February. In some areas, the snowpack is still adjusting to the load.  Snowfall since Wednesday evening may have pushed these slopes over the edge and left others on the brink of failure. 

    These slides will break 2-4 feet thick on weak layers of facets on shadier slopes and crust + facet combinations on sunnier slopes. Persistent slab avalanches can release in surprising ways. You can trigger them from flat or low-angle terrain long distances away from steep slopes, and they can break far above you. Before triggering an avalanche, you may or may not experience snowpack collapsing or other obvious signs of instability.

    Accurately evaluating whether a given slope is stable or unstable is challenging. Sadly, the only surefire way to manage this problem is to avoid avalanche terrain, especially slopes with terrain traps or severe consequences.

    (2/10/2024) This very large avalanche failed naturally sometime between Friday night and Saturday morning. The crown spans 2,000 feet of terrain and the slide ran over 1,000 vertical feet. 

Avalanche Discussion

This zone has picked up steady snowfall since Wednesday afternoon. Bouts of moderate wind have created dangerous wind slabs at upper elevations. Inconsistent, shifting wind and ongoing low-density snow may make some of these hard to identify.

We have limited information on how the weak snow surfaces under the storm snow are behaving, but reports before burial were less than glowing. There's enough new snow on these surfaces now that real avalanche problems may exist on slopes that are more sheltered from the wind. A long afternoon of sun will not only release natural loose snow avalanches but will rapidly consolidate the storm snow, quickly forming a denser slab on these weak layers that may be easy to trigger. Anticipate changing conditions today and think carefully about the consequences of being caught in an avalanche before committing to skiing or riding steep slopes.

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