Bulletin d’avalanche

Northwest Mountains

Crested Butte Avalanche Center
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Danger d’avalanche

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

Points saillants

Sporadic cornice failures could produce an isolated large avalanche.  Avoid spending time directly beneath towering cornices and travel well away from the edge of overhanging ridgelines.  Warming temperatures and sunshine may destabilize surface crusts on some slopes making it possible for you to trigger a small Wet Loose avalanche.  If you are sinking to your boot tops or deeper into wet snow, then move to a cooler aspect or lower-angled terrain.  

Problèmes avalancheux

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–3

    Large, overhanging cornices continue to fall on a daily basis under our current warming trend. Some are capable of triggering destructive slab avalanches, while others are trundling down slope entraining large amounts of snow with car-sized chunks of cornice debris.  Limit your exposure on slopes with large cornices above, and give them a wide berth if you are traveling along corniced ridgelines.  

    A recent cornice fall in Redwell Basin.  Minimize your exposure to terrain like this.  

Avalanche Discussion

Warming temperatures will help soften snow surfaces on many slopes, but cloud cover throughout the day may limit the warming potential.  Pay attention to the volume of wet loose snow at the surface to gauge the likelihood of triggering a small Wet Loose avalanche.  Ideally, you want just enough soft/wetted snow for quality riding but have supportive crusts immediately below.  Some low-elevation northerly slopes may warm enough for you to push small wet sluffs.  Use standard springtime travel advice by traveling earlier in the day and moving to colder aspects later in the day.

Cornices have randomly fallen over the past week and in a few cases, produced very large slab avalanches like this one on Gothic Mountain.  Cornice failures can be dangerous by themselves as they barrel down a slope or trigger slabs.  It is impossible to know which cornice on which ridgeline fails next, but it is best to limit your time beneath and provide a wide berth while traveling above.  Take a look through the gallery below to see more evidence of the current cornice-fall problem. 

Human-triggered Persistent Slab avalanches have slowly trended into an unlikely problem.  In most cases, very large triggers, like falling cornices or maybe an augering snowmobile, are needed to release a dangerous slab avalanche.  However, there could be an isolated slope that is sensitive to the weight of a person.  Slopes with a generally shallow snowpack, less than about 5 feet, that possess well-developed weak layers are the most suspect.  A recent example of this snowpack structure can be found in this observation from near Independence Pass (outside the CBAC forecast area).

A substantial warming trend is forecasted through the middle of this week.  Wet avalanche concerns will gradually increase each day and require backcountry travelers to start and finish early.  The brown dust is showing on the surface of many slopes and by Monday, will be on the surface of most slopes.  The dust will cause wet avalanche concerns to develop earlier in the day and produce more meltwater than a dust-free snowpack.

* In response to the warning trend, the CBAC will issue avalanche forecasts at 730 pm the night before.  Expect to see Monday's avalanche forecast Sunday night at 730pm. This allows backcountry travelers the ability to plan the night before and not need to wait until forecasts are issued in the morning.*

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