Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
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Out of date — this forecast expired 4 years ago.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

The snowpack just took another big hit, with more than 2 feet of snow and significant wind drifting over the past 2 days.  Avalanche conditions are dangerous as you climb into wind-affected terrain.  That's where you're most likely to trigger a large avalanche that fails in freshly drifted snow, and where you're more likely to find a shallow trigger point that releases the entire season's snowpack in an unsurvivable avalanche.  Choose slopes with a deep (more than 5 feet) and uniform snowpack that are protected from the wind for a lower-risk day. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3.5

    Slabs ranging from 5 to 8+ feet thick have formed around the compass and at all elevations over faceted weak layers in the lower snowpack.  The poor snowpack structure may be more sensitive in the wake of the most recent storm.  In the Northwest Mountains, the problem has become difficult to trigger because weak layers are deeply buried and hard to impact.  You are most likely to trigger an avalanche from a shallow area in the terrain, such as a rock band or where winds have formed variable snow depths.  Give yourself a wide margin for error given how 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 reduce your risk by traveling on slopes with a deep, uniform snowpack, and you can reliably avoid the problem by traveling on slope angles that are consistently less than 30 degrees.  

     

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

  • Wind Slabs

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

    Over two feet of fresh snow has been heavily transported by winds that shifted from southwest to northwest yesterday.  Large slabs up to several feet thick have formed below ridges and cornices, in cross-drifted gullies, and below abrupt rollovers.   Avoid steep terrain with signs of recent or active wind drifting.  

    1/12:  This large wind slab failed on Mt. Emmons sometime in the past 24 hours.  

  • Storm Slabs

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

    More than two feet of snow has accumulated since Tuesday morning.   The storm came in "right-side-up", trending from warm and dense to cold and fluffy.  This should make for favorable bonding of storm slabs in wind-protected terrain.  However, in very steep or unsupported terrain features, triggering a slab in the new snow remains a concern.   Furthermore, solar warming today could initiate relatively small natural sluffs in the new snow.  

Avalanche Discussion

Our avalanche problems and travel advice are quite different between the two forecast zones, so make sure you are reading the forecast for the area that you are traveling in.  This video demonstrates some of those differences. 

We did really well with this last storm, with reports of 2 to 3 feet of new snow coming from the Northwest Mountains (up to 2.5" of SWE at Schofield) and about 10" to 16" in the Southeast Mountains (up to 1.5" SWE in Gothic and 1" at Butte).  Significant wind transport was ongoing through the entire storm, and will likely continue through this morning.  Even though it is starting to feel like we live in British Columbia, the base of our snowpack is still touting its "Colorado Native" bumper sticker with large-grained, well-developed depth hoar or faceted crusts near the ground.  I expect with clear skies over the next few days, we'll uncover evidence of some large to very large natural avalanches that broke on weak layers near the ground.  Human triggering such avalanches remains a serious concern at all elevations in the Southeast Mountains and on shallow or wind-affected slopes in the Northwest Mountains.  You'll also have to manage for instabilities in the new and drifted snow.  These will be larger and more reactive in wind-loaded terrain at higher elevations.  In areas that saw more than about a foot of snow, you should also manage for lingering storm slab potential. 

The snowpack keeps growing, and we will reap the benefits of a deeper, stronger snowpack in the near future, especially in our deep zone.  Let the snowpack catch its breath after this significant loading event.  

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