Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Fri
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Out of date — this forecast expired 4 years ago.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

A few inches of snow fell overnight, but the light accumulations have not changed avalanche conditions significantly.  It's possible for you to trigger a dangerous avalanche on slopes facing northerly and easterly aspects that break several feet deep on old, weak snow.  Direct feedback for this problem has decreased in recent days, so do not expect overt signs of instability to alert you of unstable snow.  You can manage this problem by choosing lower angled slopes on northwest to north to east-facing terrain or through avoidance by selecting southerly aspects.

Avalanche problems

  • Persistent Slabs

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

    On northerly and easterly aspects, you can trigger a dangerous slab avalanche that breaks up to several feet thick on weak faceted snow that was buried last month. Slabs can be triggered remotely from below or adjacent slopes. Collapsing and cracking are clear signs of instability, although direct feedback on this problem has become less frequent. The distribution of this avalanche problem is highly variable from one steep slope to the next due to past avalanche activity. In some cases, the slope may have avalanched in late February and has yet to fill back in with enough snow to form a new slab. In other cases, the slope may have filled back in with a new slab or it has yet to release to begin with. Where the avalanche problem exists, you may be able to decrease your chance of triggering by avoiding trigger points and areas where the slab thins. When en doubt, head for lower consequence terrain or slope angles in the lower 30-degree range and less. 

    3/12:  A large persistent slab that likely failed on last Friday night from wind loading.  

Avalanche Discussion

Mother nature delivered up to 4 inches overnight with a chance at another inch or so during the first half of the day.  However, your primary concern remains the Persistent Slab problem; you can trigger a large avalanche on slopes facing the north half of the compass.  Avalanche activity over the past week has been a bit sporadic with multiple large, natural avalanches spotted in drifted terrain (natural avalanches) and a human-triggered avalanche below treeline (Elk Creek ob 1 & ob 2).  Signs of instability like cracking and collapsing are waning, but snowpack tests and profiles clearly indicate a slab and weak layer combination capable of producing a dangerous avalanche (Snodgrass observation).  Significant variations in slab thickness exist due to previous avalanche activity and snowfall amounts across the forecast area.  Some slopes that avalanched in late February might only have a foot of refill on the weak layer and some drifted alpine slopes have slabs around 4 feet thick or more above the weak layer.  These slab variations coupled with fewer signs of instability make for a challenging decision-making and assessment process for steep slopes facing northerly and easterly aspects.  The simple solution is to choose lower angled terrain on aspects that are suspect for the Persistent Slab problem.

Overnight snowfall was not enough to increase the danger rating or add any new avalanche problems but there are a few things to consider with the new snow.  Winds shifted from the southwest to northwest overnight so you may encounter shallow, isolated slabs on the east half of the compass.  These are expected to be small in size and found below ridgetops, underneath cornices, or cross-loaded in more windward gullies.  If there is more sunshine today than expected, then the new snow may become wet on steep southerly terrain and produce small loose avalanches.  Since storm totals are meager, problems in the overnight snow will remain small, isolated, and relatively easy to manage.  

And don’t forget, the 48th annual Al Johnson Memorial Telemark Ski Race is this Saturday, March 19 at Crested Butte Mountain Resort. A portion of the proceeds from the race will go to the Crested Butte Avalanche Center. Additional Information can be found here.

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