Bulletin d’avalanche

Northwest Mountains

Crested Butte Avalanche Center
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Danger d’avalanche

Wed
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 8 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Slab avalanche concerns are becoming more isolated with each passing day. Since December 8th, there has been one human-triggered persistent slab avalanche. Despite the quieting conditions, keep an eye out for suspect terrain features that may have unstable snow. Potential areas that remain possible to trigger a slab avalanche would include previously wind-loaded terrain features,  and northerly-facing slopes where you find a snowpack depth of around 2 feet (60cm) or more with strong over weak layering. 

Problèmes avalancheux

  • Persistent Slabs

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

    Snowfall and wind drifting in early December formed slabs up to a few feet thick over facets near the ground.  These weak layers are most widespread on the northern half of the compass and exist as collapsible crusts on some high-elevation southeast slopes.  Though the snowpack is adjusting under mild weather, the threat lingers on some slopes with well-developed slabs, most commonly at mid- to upper elevations and on leeward slopes.  Carefully assess the snowpack structure and consider terrain consequences before riding in steep terrain on problematic aspects.  Default to lower slope angles or travel on terrain that was bare ground through November when in doubt.

    A skier triggered persistent slab avalanche on Sunday, 12/14.  

    East aspect of Cinnamon Mountain. 

Avalanche Discussion

The most recent avalanche cycle occurred on December 6th and 7th. Since then, beginning on December 8th, three slab avalanches have been documented. Early observations following that cycle reported obvious signs of instability, including widespread cracking and shooting cracks. As the days progressed, observers have noted that signs of instability became increasingly isolated and localized. These are some highlights showing the slowly decreasing likelihood of the persistent slab avalanche problem.

The majority of these observations have come from the Northwest Mountain forecast area. While over in the Southeast Mountain forecast area, there have been no recent avalanche observations, and the avalanche danger has already trended to LOW. More people have headed towards the Ruby Range, where there is more snow to ski and ride, while in the area around Crested Butte and generally in the Southeast Mountain forecast area, the snowpack is thinner and often lacks enough snow for a slab avalanche problem. 

With the windstorm coming up tonight, we'll need to keep track of any new avalanche problems that may form. Currently, some loose facets could blow around, but otherwise, there isn't any snow available for transport. If we get some new snow tonight, that would become the snow available for transport into a new wind slab avalanche problem. 

Upcoming Events:

  • Fireside Chat: Join us at the Daily Dose on Friday, December 19th 5-7 pm to hear Matt Steen discuss professional decision making in avalanche terrain. Helicopter Skiing Lead guide manages avalanche terrain in the San Juan Mountains of Colorado. Come hear his interesting perspective.
  • Trailhead Day: We will also be at the Washington Gulch trailhead for our first Trailhead Day this Saturday from 10 a.m. to 3 p.m.

Programs like the Fireside Chat Series and Trailhead Days are made possible through funding from MetRec, STOR and the National Forest Foundation.

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