Avalanche forecast

Southeast Mountains

Crested Butte Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Dangerous avalanche conditions exist.  Up to a foot of denser-than-normal snow has accumulated since Monday night and efficient southwest winds drifted snow to leeward slopes.  You are likely to trigger an avalanche.  Avalanches can be triggered in drifted storm snow and deeper in the snowpack.  Avoid drifted terrain as there is potential for avalanches to break wide and run long distances on upper elevation terrain.  Cautious travel and conservative terrain selection are paramount for a safe day in the mountains.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–3

    Slabs ranging from 3 to 6+ feet thick have formed around the compass and at all elevations over faceted weak layers in the lower snowpack.  The poor snowpack structure produced widespread activity during stormy weather in early January.   Today, these slabs are sensitive to human triggers on some slopes.  Give yourself a wide margin for error given how active and consequential the problem is right now.   Persistent slab avalanches can propagate widely through the terrain, or be remotely triggered from low-angle slopes connected to steeper slopes.  You can reliably avoid the problem by traveling on slope angles that are consistently less than 30 degrees.

    A foot of snow and 1 inch of snow water equivalent has placed additional burden on deeper weak layers creating an uptick in sensitivity for deep breaking avalanches, particularly where winds have drifted the new snow.  Use additional caution during this loading period to avoid getting an ugly surprise.

    1/4:  A destructive natural avalanche in Red Lady Bowl broke full width on Wednesday.  This avalanche would be hard to survive.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Up to a foot of dense, new snow accumulated and been redistributed by southwesterly winds.  Cracking in the new snow in open areas is a good sign that avalanches in the storm snow are likely.  You can look for smooth, pillowy shapes to help you identify recently formed drifts.  Your safest option is to simply avoid terrain with signs of recent drifting.  Avalanches in drifted storm snow will be large enough to bury and harm you.  An avalanche in the storm snow could trigger deeper weak layers as it runs in the Southeast Mountains.

    This avalanche on Mount Emmons failed about a week ago from a bout of wind drifting.  Expect similar potential today if the snowfall forecast verifies. 

Avalanche Discussion

Areas in the Northwest Mountains have accumulated more than a foot of settled storm snow and at Schofield Pass, this storm snow contains over 2 inches of snow water equivalent.  2 inches of snow water equivalent in just over 24 hours is a substantial loading event.  Areas closer to town have seen more modest loads with around 1 inch of snow water equivalent.

More than enough volume has accumulated in leeward start zones, in both the Northwest and Southeast forecast zones, to make avalanches in drifted storm snow dangerous.  Slabs could be several feet thick and produce large avalanches that easily bury you.  Simple avoidance of drifted terrain will go a long way in reducing your risk of triggering a dangerous avalanche.

Avalanches breaking deeper in the snowpack on old weak layers, the Persistent Slab problem, have a different likelihood between the two forecast areas.  In the Northwest Mountains, deep avalanches slowly became harder to trigger prior to this storm as weak layers gained strength and slabs became thick enough to reduce the impact of a backcountry traveler on the snowpack.  Shallower parts of a slope where the slab thins offer an increased risk of impacting deep weak layers.  A rough guide to 'shallower' spots would be less than 150cm, or 5 feet, of snowpack depth.  In the Southeast Mountains, the snowpack is commonly less than 150cm which helps to explain why you are more likely to trigger an avalanche in deeper weak layers.  The chances of triggering an avalanche in old weak layers continue to increase as snowpack depths get closer to 100cm, 3 feet, as it becomes easy for you to impact weak layers through the slab.  This example from lower Cement Creek illustrates the point, where the snowpack was generally around or just below a meter and produced numerous signs of instability.

Avalanche conditions remain tricky around Crested Butte and if you plan to enter avalanche terrain you will need a sharp skill set and a thoughtful approach to terrain selection to prevent being surprised by a dangerous avalanche.

Regions covered