Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Triggering a persistent slab avalanche at the upper elevation is likely today, and natural avalanches are possible. At mid elevation, human triggered avalanches are possible, especially in Seeley Lake and the central Bitterroot.

Look for red flags like cracking, collapsing, whumfing, or recent avalanches. If you encounter these, stick to slopes under 30 degrees in slope angle.

Temperatures are warming but still cold enough that any injury or gear problem can make a small avalanche or injury potentially life-threatening.

 

Avalanche problems

  • Persistent Slabs

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

    Human triggered persistent slab avalanches are likely today on middle and upper elevations. Various overlapping buried weak layers, including surface hoar, near surface facets, and depth hoar, exist on all aspects at upper elevation and north through east aspects at mid elevation. We are beginning to get reports of multiple large natural avalanches from the past few days, likely failing on these layers.

    It will be possible to remotely trigger an avalanche from above, below, or to the side of slopes. 

    You can recognize persistent weak layers by digging into the snowpack and looking for a dense slab on top of weak, sugary snow. Buried surface hoar can be more difficult to identify in a snowpit but often appear as a thin horizontal line across the snowpit wall face. 

    Red flags include wumpfing, collapsing, shooting cracks, and recent avalanches. If you encounter any of these or find a poor snowpack structure of buried weak layers below a slab, stick to slopes under 30 degrees.

  • Wind Slabs

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

    Triggering an avalanche on a wind slab is possible today.  During the last storm, strong shifting winds built overlapping wind slabs on all aspects at mid and upper elevations.  Although wind was the driving factor in slab formation, in many areas, these wind slabs sit on persistent weak layers and the wind slab problem is interwoven with the persistent slab problem.

    Wind slabs are hard slab avalanches that often break above you and are very difficult to escape. Any wind slab also has the potential to step down onto deeper buried persistent weak layers, which can cause a large destructive avalanche. 

    Look for snow that feels firm or has a hard slab on top of less cohesive snow. It may not always be obvious at first glance, as fresh snow will conceal older wind slabs. 

    Cracking, collapsing, or slopes with a smooth, rounded appearance are indicators of wind slab potential. If you encounter these, stick to slopes under 30 degrees.

Avalanche Discussion

After some downright bitter cold temperatures, things are warming up today.  All zones should see temperatures climb above zero today before dropping again tonight. The chances of new snow on Wednesday seem to be improving, with the potential for up to a foot in the Bitterroot and Rattlesnake.

As we transition from a week of turbulent weather to a period without new snow, a shift in mindset is crucial. The peak storm instability, particularly in the wind slab, has subsided. However, we are now left with multiple persistent weak layers and an overall poor snowpack structure. These issues will improve over time. The downside is that this requires patience, time, and discipline to resist the temptation of skiing or riding on steeper slopes.

During times of prolonged considerable danger or persistent weak layer challenges, there's a natural inclination to test limits. It starts with a 30 degree slope, then a 33, followed by a 34, and so on until it avalanches. Or, most of your party skis it, and then the last person triggers the avalanche.   It's essential to resist this urge and opt for low-angle skiing and riding while allowing the snowpack to strengthen.

The snowpack is slowly building on lower elevations. As much of the new snow fell on dirt, there are no persistent weak layers with a slab sitting on top. For this reason, low elevations are at a low danger for the day. Continue to keep an eye out for ground hazards such as downed logs, stumps, and rocks. They may exist under new snow and be obscured from view.

On January 11th, a skier passed away in an avalanche near Steven’s Peak in Shoshone County, Idaho. We would like to extend our condolences to family and friends.

Let us know what you are seeing in the mountains by submitting an observation. Even just a photo or letting us know how much snow fell helps us greatly!

Ski and ride safe!

 

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