Bulletin d’avalanche

Northwest Mountains

Crested Butte Avalanche Center
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Danger d’avalanche

Mon
Alpin
1 · Faible
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Human-triggered slab avalanches are unlikely, and avalanche conditions are generally safe around the range.  Intact slopes that did not avalanche during last week's natural cycle could produce a triggered avalanche from a shallow spot on the slope or in extreme terrain where the snowpack is not supported.  You can reduce the chance of being unlucky by avoiding very steep slopes that appear to have variable snow depth.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    1–2

    Last week's storm produced a widespread avalanche cycle on November 26-27. Those slabs have now settled to 1 to 3 feet thick over faceted snow that formed earlier this winter. The snowpack gradually adjusted over the 10+ days since the storm cycle: stability tests are improving, and signs of instability have diminished as the problem has become isolated and difficult to trigger. The most problematic slopes face west, north, and east. Slopes with consistently deep and uniform snowpacks or slopes that naturally avalanched last week offer lower-risk options for steep terrain on those aspects.  Move to smaller, less consequential terrain features when in doubt.  

    A remotely triggered persistent slab on a west-facing slope above the Slate River was triggered on 11/28. This slope survived the natural cycle and had the necessary ingredients: a cohesive slab over weak, early-season snow.

Avalanche Discussion

The danger rating dropped to LOW at all elevations in the Northwest Mountains.  The likelihood of human-triggered slab avalanches reached a level to fit 'generally safe' avalanche conditions.  This is a product of the widespread natural cycle during the Thanksgiving storm removing the problem for a large portion of the steep slopes in the zone.  Snowpack evidence points towards an unreactive snowpack on the remaining intact slopes.  These factors make it very unlikely for a person to trigger a large avalanche.  Exceptions always exist in the world, and if you are considering riding in extreme terrain that is rocky, variable in depth, and high in consequence, be sure to evaluate the snowpack before committing.  LOW danger allows for small avalanches in isolated places and extreme terrain, which certainly applies to our current conditions.

In the Southeast Mountains, the danger rating remains MODERATE at upper elevations.  The natural cycle produced fewer avalanches, particularly in the Brush Creek and Cement Creek drainages, compared to the Northwest Mountains.  More slopes remain intact, with slabs resting above weak basal layers.  The shallower snowpack likely means a slower adjustment toward equilibrium.  With more intact slopes and suspected higher sensitivity, the Southeast Mountains danger rating remains at MODERATE.  We have less snowpack data from the shallower areas, thus creating greater uncertainty about the likelihood of human-triggered avalanches on intact slopes.

Events: The Beacon Brush Up is then behind the Crested Butte Community School on Sunday from 9 a.m.- 2 p.m.  Details are here. 

Régions couvertes