Bulletin d’avalanche

Southeast Mountains

Crested Butte Avalanche Center
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Danger d’avalanche

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

Points saillants

Dangerous avalanche conditions exist and an Avalanche Warning is in place through Sunday night.  Conservative terrain choice and careful route finding are paramount.  You are most likely to trigger an avalanche in the recent storm snow, but the possibility exists for avalanches to break deeper in the snowpack.  Heavily drifted slopes at upper elevations offer the greatest hazard.  Today is a good day for simple terrain choices with limited exposure to avalanche terrain.  

Problèmes avalancheux

  • Storm Slabs

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

    Storm totals of up to 30 inches with 3" of Snow Water Equivalent exist in both forecast areas from only a 48-hour period and a handful more inches are expected on Sunday.  Snow densities are well above average for Crested Butte.  Temperatures were colder at the beginning of the storm Friday morning and warmed throughout Friday and remained warmer overnight.  With impressive, dense storm totals, rapid loading, and warming temperatures through the storm expect human-triggered avalanches to be likely.  Avalanche size will commonly be large enough to bury, injure, and kill you.  Natural avalanche activity could occur on slopes while active wind-loading occurs.  A Storm Slab could act as a trigger for a deeper avalanche.

    3/11:  Several Storm Slab avalanches ran naturally during a cycle on Saturday morning.  Gibson Ridge.

  • Persistent Slabs

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

    The current storm cycle could potentially awaken deeper weak layers in the snowpack.  Avalanches that break into weak layers in the middle or bottom of the snowpack would grow to dangerous sizes and be difficult to survive.  Uncertainty exists about whether or not deeper weak layers will re-activate during this storm but this observation from the Southeast Mountains, from Saturday, suggests that the problem may exist.  The picture will become clearer once the skies open up and more observations can be made.  

    3/11:  This avalanche was observed on Double Top Mountain (correction: this was mislabeled this morning as Cement Mountain).  Although hard to be certain, it appears to have broken deeper than the recent storm snow.

Avalanche Discussion

Northwest Mountains:  In the deep snowpack Northwest Mountains, the primary concern lies with the recent snow.  Instabilities at the base and in the middle of the storm snow have been noted by observers and confirmed by natural avalanche activity on Saturday; Irwin Guides cat-ski tenure produced avalanche results through explosive control work.  The storm snow clearly accumulated in an "upside down" manner with denser snow accumulating above lower-density snow.  Storm snow weak layers often improve in just a few days but could continue to produce large avalanches today.  Leeward terrain remains the most suspect, due to southwest-to-west winds depositing very dense slabs that could be close to 4 feet thick on well-drifted slopes.  Carefully evaluate the snowpack and select conservative terrain to help reduce your risk of triggering a dangerous avalanche.  If you are in doubt about your chances of triggering an avalanche then reduce slope angles to less than 30 degrees and surf low-angled powder.

Southeast Mountains:  Observations from yesterday suggest that a Persistent Slab problem exists in the Southeast Mountains in addition to Storm Slabs.  Check out this observation from the Brush Creek area with natural avalanche activity involving weak layers deeper in the snowpack.  Additionally, a natural avalanche impacted Cement Creek Road (past the winter trailhead on the XC track) that may have involved Persistent Weak Layers.  Storm totals were very similar between the Northwest Mountains and the Southeast Mountains over the past 48 hours, but there is a clear increase in hazard in the Southeast Mountains due to the potential for avalanches to "step-down" into deeper weak layers.  Consider the possibility of triggering an avalanche remotely and it breaking wider and deeper than you expect.  Conservative terrain selection, like slope angles 30 degrees or less, without significant overhead hazard, is paramount for areas near and to the east of Crested Butte.  The risk of natural avalanche activity has decreased, but the threat of large human-triggered avalanches will likely linger longer in the Southeast Mountains.  Slopes that face south or southwest have a reduced threat of Persistent Slab avalanches.

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