Avalanche forecast

Northwest Mountains

Crested Butte Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Human-triggered avalanches continue to occur daily. Many of those avalanches have been remotely triggered from lower-angled slopes connected to steeper slopes. Dangerous avalanche conditions exist, and conservative decision-making is recommended. 

Avalanche problems

  • Storm Slabs

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

    We have observed a few lingering soft slab avalanches occur on southerly-facing slopes, releasing on the old snow surface around 1 to 2  feet down. So far these have all been small avalanches. Consider this potential avalanche problem if you are riding steep southerly facing slopes. 

    A pair of soft slabs on a southeasterly slope on Snodgrass look like they either ran naturally on Friday or were remotely triggered by a ski track about 100 yards away. 

    Photo: Zach Guy

  • Persistent Slabs

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

    A new round of weak layers was 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 more 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, but these obvious signs of instability will not always show themselves before an avalanche releases.

    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.  

Avalanche Discussion

Before the weekend arrived, our avalanche database was piled with recent human-triggered avalanches. Now that it is the weekend and more people will be out, we can expect to add to it. Thankfully all those reported avalanches have been relatively small in size. The potential for large and even very large avalanches is very real, and the larger natural avalanches that have occurred are a good example. Good terrain selection has likely contributed to the documented human triggers remaining small. Don't forget, that even a small avalanche can pile deeply in a terrain trap, and that was the case last Thursday when a snowmobiler was fully buried, outside our forecast area, on the Grand Mesa. There have been other recent close calls near Ashcroft and the Anthracites. 

The main weak layer contributing to the recent avalanches is a layer of surface hoar buried earlier this month. Even fist hard soft slabs have been remotely triggered on this fragile weak layer. If those soft slabs continue to settle, avalanches may become harder to trigger but we may also see wider propagation in those avalanches. In the NW Mountains this weak layer is buried deeper and is already becoming harder to trigger, but with the thicker slab comes a bigger pointal avalanche size. This particular weak layer will most commonly be found on the northern half of the compass. Avalanche activity has been less common where this weak layer doesn't exist, such as lower elevation southerly facing slopes. However, there are still a few reported avalanches so far on SE and SW aspects. 

The weak layers are the same across the Northwest and Southeast Moutain forecast areas. The difference is the amount of snow that has accumulated on top of those weak layers in the last week. In the NW Mountains the 2/2 interface is more commonly buried 2 to 4 feet deep, while in the SE Mountains, the 2/2 interface is more commonly buried 1 to 2 feet deep. Again, thicker slabs are typically harder to trigger, but they will also produce bigger avalanches. 

Regions covered