Bulletin d’avalanche

Southeast Mountains

Crested Butte Avalanche Center
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Danger d’avalanche

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

Points saillants

Knowing which slopes are more likely to avalanche on suspect aspects is difficult.  The variation in snowpack from one feature to another due to seasonal snowfall totals, wind, and previous avalanche activity creates a complicated scenario.  Don't rely on assessments from low-angled terrain to persuade you to enter steep slopes, as it often doesn't represent the snowpack in start zones.  If you choose to play in avalanche terrain, you can reduce the consequences of an avalanche by selecting small slopes with clean runouts; the SAFER way to manage the uncertainty is to select lower-angled terrain not directly below steep slopes or avoid problematic aspects and elevations.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–2.5

    Slabs averaging 1 to 2 feet thick in sheltered terrain and larger in wind-loaded terrain are possible to trigger where they formed over well-developed facets and collapsible crusts on west, north, and east aspects. Additionally, wind-loaded slabs have been failing above buried crusts on high elevation, southerly aspects. Slab behavior is challenging with variable and deceptive feedback, remote triggering potential, and wide propagation across terrain features.  You can reliably avoid the problem on slope angles less than 30 degrees without steeper slopes above you, and most mid to low-elevation southerly aspects lack the problem.  

    This large persistent slab avalanche ran on the southwest side of Hunter Hill last weekend. 

     

Avalanche Discussion

Dangerous human-triggered avalanches remain a threat at MODERATE danger.  The number of dangerous slopes has slowly decreased with time for various reasons.  Some slopes on the Persistent Slab distribution rose lack a slab due to wind erosion and the faceting process weakening the slab.  Other slopes lack a slab due to avalanche activity during the natural avalanche cycles of Thanksgiving and Christmas.  Some slopes have all the right ingredients for a dangerous human-triggered avalanche. This observation from Carbon Peak documents multiple collapses and shooting cracks, a recent natural avalanche on WSC Peak, and this observation from West Brush Creek clearly illustrates that the snowpack remains dangerous on some terrain.  A highly variable snowpack exists from one slope to another, creating complex decision-making.  

In sheltered areas, snowpack depths between about 90cm and 120cm (3 to 4 feet) appear to be the most sensitive.  Collapses and shooting cracks continue to be reported around these depths.  Slopes with less than 80cm often lack a slab due to previous avalanches or degradation from faceting.  If you find one of these slopes without a slab, expect to trigger Dry Loose avalanches.  The hard part is identifying snowpack depths in start zones, as it requires you to expose yourself to avalanche hazards to find out; that's not a safe way to gather information.

As you move into wind-affected terrain, signs of instability will likely decline or be absent until the moment you trigger an avalanche.  Playing in steep avalanche terrain at upper elevations remains a roll of the dice with no good way to gather information about the likelihood of a triggering avalanche.  Expect the potential avalanche size to increase in wind-drifted terrain at upper elevations and increase the consequences if you were to trigger a slide.

Sometimes, Mother Nature creates a 'lemon' snowpack with few predictably safe options in steep terrain.  Avalanche conditions will become more predictable at some point this season, and safer terrain options will increase.  However, don't expect this to happen in the near future. For more insights and a recap of last week, our weekly summary is up

Régions couvertes