Avalanche forecast

Southeast Mountains

Crested Butte Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Skiers triggered a couple of large avalanches on wind drifted slopes yesterday.  Avalanches this week have followed a clear pattern of failing on slopes that were stressed by our recent wind event.  Slabs in leeward terrain features are breaking on weak layers in the middle of the snowpack and in some cases, weak layers near the ground.  Avoid steep slopes that look or feel recently wind-loaded, characterized by denser, thicker snow on the snow surface.   Soft, wind protected snow below treeline offers the safest riding.  

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2.5

    Slabs up to several feet thick have the potential to fail on faceted weak layers near the ground and in the middle of the snowpack. Problematic weak layers exist on most aspects.  The slabs are more common and most sensitive on leeward terrain from recent west to northwest winds.    Persistent slabs are notorious for erratic feedback and unusual behavior, such as remote triggering and wide propagation. To reliably avoid the problem, choose routes that keep you off and out from under terrain steeper than about 30 degrees where you find stiff and cohesive slabs. In steeper terrain, you can reduce your chance of triggering an avalanche by avoiding slopes with obvious signs of recent drifting such as thick, denser snow at the surface.

    This persistent slab avalanche wrapped from shady to sunny aspects and broke on weak layers near the ground. This a good example of the potential size and widely propagating behavior of persistent slabs breaking on weak layers near the ground.

Avalanche Discussion

Forecasters yesterday intentionally triggered a couple of large slab avalanches on Mt. Baldy and Mt. Emmons.   In both cases, they were slabs of drifted snow that formed recently over our mid-December weak layers.  Because the snowpack has been rotting away in sheltered terrain, the slabs were able to entrain a significant amount of weak snow.  Problematic slabs are more common and larger near and above treeline.  At those higher elevations, the recent wind event has redistributed the problem away from wind eroded slopes and onto wind loaded slopes.  This video demonstrates how you can visually identify and avoid the most concerning terrain.  

Persistent slab instabilities are far less common below treeline.  In wind-sheltered terrain, the lack of loading in the past two weeks has caused the persistent slab structure to generally go dormant, evidenced by a lack of avalanche activity in that type of terrain in the last two weeks and improved stability test results.  However, not all slopes below treeline are wind sheltered.  The arctic blast last week mixed strong winds into lower elevations, and in terrain with large fetches, formed sensitive hard slabs over weak-faceted snow.  These issues are fairly isolated and easy to recognize by paying attention to surface textures and snow quality.  There are a few examples in our gallery below, caused by strong downvalley winds out of the northwest.   If you are riding over dense, slabby snow at lower elevations, you've found the problem.  Seek the softer snow for safer riding. 

A powerful winter storm starting on Tuesday night will cause the avalanche danger to rise dramatically on Wednesday, and dangerous conditions are expected to continue through next weekend.  Plan accordingly.  

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