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

You can trigger a dangerous avalanche today.  Avalanches could break just in drifted storm snow or deeper in the snowpack.  You can release an avalanche from a long distance or from below a slope.  Signs of instability, like whumpfing, have become less frequent but don't allow this to trick you into a false sense of security.  You can reduce your risk of triggering an avalanche through conservative terrain selection and by placing a wide margin between your group and steep slopes nearby or above.

Avalanche problems

  • Persistent Slabs

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

    Storms this month built large persistent slabs that are sensitive to human triggers and could release naturally today.  There's a widespread weak layer of facets and faceted crusts buried by 2 to 3-foot slabs on west to north to southeast aspects. Concerns also exist on some alpine south and southwest-facing terrain features.  Slabs are largest in leeward terrain at higher elevations.   Persistent slabs are notorious for erratic feedback and unusual behavior, such as remote triggering and wide failures.   To avoid the problem, choose routes that keep you off and out from under terrain steeper than about 30 degrees that hold old, weak snow near the ground.    

    A recent persistent slab that 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 our current persistent slab problem. 

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    New snow and northwesterly winds have formed fresh drifts on leeward terrain features.  Watch for blowing snow to clue you into developing instabilities as well as cracking in the storm snow.  Small wind slabs have the potential to step down and trigger a larger persistent slab avalanche where the problems overlap. 

    Look for blowing snow like this to warn you of fresh wind slab formation.

Avalanche Discussion

Snowfall and gusty northwest winds continued on Tuesday.  Areas to the west and north of Crested Butte, in the Northwest Mountains, received more than a foot of snow over the past 36 hours while terrain closer to town and the Southeast Mountains have only snagged 2-5 inches.  Significant natural avalanche activity is not anticipated, but there could be a few highly drifted alpine slopes that get pushed past their tipping point and release naturally.

Slabs 2 to 4 feet thick formed over the past two weeks on top of early season weak layers and produced natural avalanche cycles and human-triggered avalanches.  Signs of instability like whumpfing and cracking were relentless initially, but as time passed these overt signs of danger have slowly become less common.  Weak layers have yet to gain strength (this ob from near Beckwith Pass or this one from the Pittsburg area show basal facets remain Fist hard).  The slabs overlying the weak layer have become stronger which is why there are fewer signs of instability.  The stronger slabs simply make avalanches larger in size and help mask the signs of danger.  Do not let fewer signs of instability lull you into complacency.

To combat the unpredictable behavior of Persistent Slab avalanches and reduce your risk of triggering an avalanche make conservative terrain choices.  Here are some things you can do;  pick slope angles around 30 degrees or less that are not below steeper terrain, or you can choose south and southwesterly terrain at lower elevations which are less likely to have basal weak layers and produce deep failing avalanches.  Patience and disciplined terrain selection are the best tools to combat the current Persistent slab problem.

 

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