Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

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

It has been a busy week for avalanches, with a few close calls.

You can trigger a persistent slab avalanche at mid and upper elevations on various overlapping weak layers. Look for red flags like cracking, collapsing, and recent avalanches. Dig in the snow and look for a slab over weak, sugary snow. If you encounter any of these, stick to slopes under 30 degrees.

Wet snow avalanches remain a possibility at low elevations and into mid elevation. Be especially cautious in areas that did not refreeze overnight. Point releases and generally wet and unsupportable snow are signs that larger wet snow avalanches will follow. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2.5

    Triggering a persistent slab avalanche is possible today at mid and upper elevations. The snowpack has overlapping weak layers of buried facets, crust/facet combinations, and buried surface hoar giving all aspects at least one problem layer. It has been a busy week with both natural and human triggered avalanches on all these layers. This recent avalanche activity re-enforces the need for caution and avoidance. 

    Avalanches have been especially active in the elevation band where recent warm temperatures have warmed previously dry snow, often at the upper end of the mid elevation band. 

     Some layers, like the buried surface hoar, have produced obvious red flags and widespread collapsing. Others, like the depth hoar at upper elevation, have shown no red flags before producing a large avalanche. 

    Take the time to dig and investigate the snowpack where you are looking to ski or ride. If you find a slab over weak, sugary snow, stick to slopes under 30 degrees. Surface hoar can be identified as a thin grey line across your snowpit wall. If you find it, be especially cautious. Buried surface hoar can create avalanches for weeks and is a common weak layer in fatality avalanches. 

    (1/20/2024)

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–1.5

    After a week of warm temperatures and a lack of solid refreeze last night, wet loose avalanches are likely at low elevation in areas with enough snow depth to produce avalanches.

    Today, warm temperatures and the potential for low elevation rain will make triggering a wet loose avalanche likely, but the size will be small. Even a small avalanche can be trouble if it pushes you into terrain traps like streambeds or gullies. 

    If you are sinking into wet, unsupportable snow, expect wet snow avalanches in steeper terrain and be aware of the slopes above you.

Avalanche Discussion

The weather has been generally mild since the last forecast on the 21st, with warm temperatures, light to moderate winds, and a few inches of new snow. 

At this point, we must accept our unusually, potentially even historically,  weak snowpack. Danger remains considerable at upper elevation due to the reactivity and likelihood of triggering an avalanche. Multiple close calls involving skier and rider triggered avalanches in the past week re enforce the need to dial back terrain choices and be suspicious of avalanche terrain.

Some avalanches of note in the past week:

Large remote triggered avalanche in East Seeley

Snowmobile remote trigger in central Bitterroot

Skier triggered avalanche outside Lost Trail resort

True to form, from depth hoar at the upper elevation, buried crust/facet combinations on south aspects, and buried surface hoar at the mid and upper elevation, persistent weak layers continue to produce avalanches. Especially concerning are areas with buried surface hoar. Very calm conditions at the start of the first January storm preserved a layer of surface hoar across all zones, but especially around Lost Trail Pass, where it has already produced multiple avalanches. If we look back at avalanche fatalities across North America, a common thread is fatality avalanches on buried surface hoar in areas that don’t often deal with a lingering surface hoar problem. 

A full report on the fatality avalanche on Lookout Pass has been released. Take the time to read the report and recognize that this could have been any of us. This party did almost everything right. While using good travel practices and exposing themselves to as little avalanche terrain as possible, a small avalanche stepped down and produced a much larger avalanche on a deeper weak layer. These conditions present in this incident are very similar to what we have across our forecast zones. 

Please continue to submit observations. We appreciate every observation we get, and it really does help us get a better understanding of what is happening across the forecast area. 

Ski and ride safe. 

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