Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
View on map

Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
Open full map
Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The storminess from the past few days has created dangerous avalanche conditions.  You are likely to trigger an avalanche.  Avalanches may break just in storm snow, in the middle of the snowpack, or near the ground in some places.  Drifted slopes present the greatest danger and avalanche size.  Thoughtful and careful snowpack assessment is required to safely play on steep terrain.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–3

    Many slopes have weak snow at the bottom of the snowpack, and new slabs have formed over persistent weak layers in the upper snowpack which are reactive to the weight of a human. A triggered avalanche in the upper snowpack could step down to deeper weak layers near the ground, become much larger than expected, and produce a destructive avalanche. This avalanche problem 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

    Recent warm temperatures combined with the recent storm snow created widespread surface slabs. Avalanches averaging 8 to 20 inches thick will be likely to human trigger on many slopes near or above 35 degrees in steepness. Careful snowpack evaluation and cautious route finding will be essential when traveling near avalanche terrain.  Aspects and elevations where the Storm Slab problem overlaps with the Persistent Slab problem could result in a surface avalanche 'stepping down' to deeper weak layers.

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

Avalanche Discussion

Natural and human-triggered avalanches were reported in the past two days.  HIGH danger (level 4 of 5) was forecasted on Wednesday and Thursday.  Visibility has been obscured so uncertainty exists if the HIGH danger criteria of a widespread natural avalanche cycle occurred.  With continued poor visibility, and another potent storm arriving tonight, we may not get the answer.

Here is what we do know; backcountry travelers have triggered avalanches in the storm snow, on weak layers just below the recent storm snow (Snodgrass, Anthracite Range), and at least one natural avalanche broke near the ground on a well-drifted slope on Gothic Mountain.  Additional natural avalanches were observed on Gothic and Mount Emmons yesterday.

The most dangerous places to travel are those where westerly winds have drifted the new snow and placed the greatest burden on the snowpack; the natural avalanche from Gothic that broke near the ground is a great example of this danger.  Additionally in sheltered terrain, slopes that are known to harbor weak layers like Surface Hoar, Near-Surface Facets, or faceted bed surfaces from previous avalanches now have slabs resting above from recent snowfall and are simply waiting for a trigger.  A very careful snowpack assessment is required if you attempt to enter steep terrain; you will need to ensure that weak layers are not present in or below the recent storm snow.  Signs of instability like cracking and collapsing are clear indicators of unstable snow, but may not always be present to give an obvious warning.

A potent winter storm with an impressive amount of moisture will barrel into western Colorado this evening.  The avalanche danger is expected to rise to HIGH sometime on Saturday thus an Avalanche Watch has been issued.  Anticipate widespread natural avalanche activity and very dangerous travel conditions.

 

Regions covered