Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Human-triggered avalanches have occurred every day for the last week. Natural avalanches have also released. We can expect more of the same today as dangerous avalanche conditions exist. It is recommended to keep those terrain choices conservative while further considering your overhead hazards as avalanches can be remotely triggered or release naturally above you. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3

    A new round of weak layers were buried on February 2nd. These weak layers consist of surface hoar and facets on most east, north, and west-facing slopes, and potentially faceted crusts on high-elevation southerly aspects. This interface is now buried 2 to 4 feet on average. In the last week, there have been daily human-triggered avalanches and continued natural avalanche activity. This avalanche problem can be remotely triggered from flat terrain, or propagate widely across terrain features.  Shooting cracks or collapses are a clear sign of danger.

    There are old faceted weak layers near the ground that are more stubborn to human triggers. These dense old slabs may not give warning signs before they release; they are most commonly triggered from terrain features with shallow or variable snowpacks, or if avalanches in the upper snowpack gain enough mass to step down.  This problem is generally up to D3 in size.  

    2/4: This avalanche on Mt. Axtell exemplifies our newest generation of persistent slabs (recent storm snow breaking on facets or surface hoar), which then stepped down and triggered older hard slabs deeper in the snowpack on old weak layers near the ground.  

  • Storm Slabs

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

    Density changes within the recent storm snow will keep the possibility for soft slab avalanches releasing in the upper snow snowpack. You will primarily find yourself managing this avalanche problem on low elevation southerly facing slopes, otherwise, this avalanche problem is overlapping the more dangerous persistent slabs. This avalanche problem will be most suspect on steep slopes near 40 degrees, or in terrain that has some wind effect and additional wind-loading. 

    A skier triggered Storm Slab from this past Saturday.  Similar-sized slabs can be triggered on low-elevation southerly slopes.

    Photo: Jake Hutchinson

Avalanche Discussion

As of 5am, 24hr snow totals are in the 2" to 5" range with up to .4" SWE. On Friday we will slowly start to move away from peak instability as we move away from the heavier precipitation rates that occurred on Wednesday into Thursday. Natural avalanche activity today will be driven by any additional wind loading, or if we see a burst in precipitation rates this morning. 

Snowpack evaluation is tricky as the layering in the snowpack is so variable from one slope to the next thanks to so much avalanche activity in the last week or even the last month. If you are traveling in a suspect area for the persistent slab problem, be careful of thinking a lack of shooting cracks or collapses is a sign of better stability, as conditions could change quickly from slope to slope.

The weak layers are the same across the Northwest and Southeast Moutain forecast areas. What is different is the amount of snow that has accumulated. For example, since 2/2. Schofield Pass has accumulated about 2.6" of SWE while Butt Snotel has accumulated about .8" SWE. Of course, variations in total snow accumulations exist in both forecast areas but we can use those two points as an example. In the Northwest Mountains, the persistent slab avalanche problem is more reactive and widespread. In the Southeast Mountains, the same avalanche problem will be most problematic in areas that are seeing additional wind loading. While in wind-sheltered areas, the slabs are so soft that variability will exist where some slabs may not be able to propagate a fracture as well. 

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