Avalanche forecast

Southeast Mountains

Crested Butte Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Dangerous avalanche conditions exist.  You can easily trigger an avalanche in the recent storm snow and it is possible for a few natural avalanches to occur.  Some slopes could break deeper than the storm snow and produce a very large avalanche.  The snowpack needs more time before you can safely enter steep terrain.  Choose lower-angled slopes, around 30 degrees or less, and maintain a conservative mindset.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    Settled storm snow depths since Monday 3/20 range from 2 to 3 feet.  Snowfall densities increased throughout the storm creating denser snow above lighter snow; a clear recipe for Storm Slab avalanches.  The old snow surface (3/20 interface) consisted of near-surface facets and a collapsible crust which will help maintain sensitive avalanche conditions in the upper snowpack and allow for wider propagation.  Low elevation due south-facing slopes having thicker crusts and they will be less likely to collapse. A triggered avalanche will have lots of snow available for entertainment and quickly grow in size as it runs through the terrain. This isn't an avalanche problem that you can outsmart with a specific snowpack test and a high skill level of terrain management will be required. 

    A large avalanche that ran into lower-angled terrain earlier this winter. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–3

    There are several faceted weak layers in the snowpack that remain a concern in some terrain. The most concerning slopes include those that held an unusually shallow and weak snowpack prior to our March storms (like Round Mountain), where snow depths are currently less than about 5 feet (150cm) deep, or in wind-effected terrain with variable snow depths (like Teo or Carbonate Hill).  There are also recently buried faceted crusts in the upper snowpack on easterly and westerly-facing slopes that are just developing an issue (like Whetstone). A natural or human-triggered avalanche in the recent storm snow could further step down to these deeper weak layers and produce an unsurvivable avalanche. 

     

Avalanche Discussion

The snowpack endured another major loading event and an Avalanche Warning just expired this morning.  Settled storm totals generally range from 2 to 3 feet deep with 2 to 3.6 inches of snow water equivalent.  Southwest winds on Wednesday were strong to extreme with significant drifting at upper elevations and even a period of strong valley bottom winds in the afternoon that drifted snow in less common areas at low elevations.  Meteorological evidence points squarely to dangerous avalanche conditions and necessitates conservative terrain selection.  Avoid terrain steeper than about 30 degrees and avoid travel beneath large, heavily drifted avalanche paths.

Limited observations from yesterday verified very easy to trigger avalanches in the storm snow.  Take a look at these observations from Snodgrass and the Irwin area to see the clear evidence of very dangerous avalanche conditions.  Observers reported multiple human-triggered avalanches breaking at the base of the storm snow.  Storm Slabs have enough mass to bury, injure, and kill you on many slopes.  Obscured visibility did not allow for views into alpine terrain or heavily drifted slopes, but given the sensitive nature of the storm snow from the observations referenced above, there is little doubt dangerous natural avalanche activity occurred on wind-loaded slopes.  Natural avalanche activity could occur today on slopes that receive additional wind loading.

In addition to avalanches breaking in the storm snow, there is a real threat of avalanches breaking deeper in the snowpack and creating very large avalanches that grow to a destructive size.  Persistent slab issues have caught numerous groups by surprise in the Elk Mountains just prior to the arrival of the recent storm, and unfortunately, two of the accidents resulted in fatal outcomes. One accident was near Marble and the other near Aspen Highlands.  In the deeper zone, the issues appear to be tied to a near-crust faceted layer at the base of our two recent storms (March 10th interface), about 2 to 3 feet deep below the recent storm snow.  Our forecast team checked out the impressive crown on Mt. Baldy,  which was notably thicker due to extensive wind drifting.  This issue has been particularly challenging to forecast because the layer was not obvious on the snow surface prior to its burial, so we don't have a clear map of its distribution.  Furthermore, it has provided very limited feedback in the way of collapses or unstable pit results.  Our best tool right now for plotting the problem is observing avalanche activity patterns, which have been most common on east-to-south aspects. In our shallower SE Forecast area, we are painting a broader distribution because we are also concerned about issues on northerly terrain where the snowpack is shallow and/or variable in depth.  Sunday's accident in Maroon Bowl is a good example of that.

 

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