Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Sun
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

The red flag is flying, as increased winds and continued accumulating snow have combined to create very dangerous avalanche conditions. The threat of large to very large natural avalanches will increase throughout the day. This avalanche activity could impact some backcountry roads and run into low-angled terrain. Sizable slab avalanches will also be sensitive to the weight of a human and could be triggered from low-angled slopes connected to steeper slopes. Travel in avalanche terrain is not recommended. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–3

    Large to very large avalanches are expected to be reactive on persistent weak layers in the middle of the snowpack, and may even step down to weak layers at the bottom of the snowpack. This avalanche problem will be the most reactive on north to east to southeast-facing slopes. Southerly and westerly facing terrain is developing this avalanche problem and for the moment, remains slightly less likely than the other side of the compass. Persistent slab avalanches can propagate widely through the terrain, or be remotely triggered from low-angle slopes connected to steeper slopes.

    Avalanches could step down into deeper weak layers such as this human-triggered avalanche on 12/27.

  • Storm Slabs

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

    Yesterday the snow surface consisted of low-density goose feathers. Overnight temperatures have been on the rise, and today's snow will be heavier than the snow below. Newly formed soft slab avalanches may be reactive to human triggers around the compass. These slabs will most commonly release on slope angles in the mid-30 degree range and steeper. A triggered avalanche in the upper snowpack can also step down into the deeper persistent slab avalanche problem.

    Shooting cracks or a collapsing snowpack are obvious red flags that the snowpack is unstable. 

Avalanche Discussion

The incremental loading has kept the forecast team on edge all week. This snow has been accumulating on a weak foundation that is untrustworthy. The house will fall down, and it has been difficult to predict just when that will happen. The most notable change in the weather overnight is an increase in wind speeds. Southwest winds have been averaging in the 20 mph range with gusts into the 40's. 11,000ft winds are averaging in the single digits to teens and gusting into the 20's and 30's. With ample amounts of snow available for transport, these increased winds will be the main driver of the natural avalanche cycle expected today. 

Continued accumulating snow in wind-sheltered areas is also nearing a tipping point for the persistent slab avalanche problem in these locations. As of yesterday, we had yet to see this avalanche problem become reactive in wind-sheltered locations. However, those conditions could change just as quickly as flipping on a light switch once enough snow accumulates. Once that switch is flipped you don't want to be anywhere near those slopes. 

Potential avalanche size has notably increased this week. There is a lot of volume that has accumulated in start zones. A Triggered avalanche will now be more commonly large and destructive. Since December 27th, Schofield Pass has accumulated 2" of water or 2 to 3 feet of snow. While Butte Snotel on Mt Crested Butte has accumulated 1.3" of water or 1 to 2 feet of snow. 

HIGH avalanche danger will likely extend into Sunday morning, before temporarily decreasing in between loading events. We will of course re-evaluate danger ratings in the morning. 

Regions covered