Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

You can trigger a persistent slab avalanche at middle and upper elevations on overlapping weak layers of buried facets, facet/crust combinations, and buried surface hoar. 

Look for red flags like cracking, collapsing, or recent avalanches. As the avalanche problems become less obvious, it is worth digging in the snow and looking for poor snowpack structures with a firm slab over weak, sugary snow.  If you encounter any of these, stick to slopes under 30 degrees.

Wet loose avalanches are likely today at low elevations in areas that did not see a re-freeze last night. Mid elevation wet snow is likely in areas of dense cloud cover and without wind today.

Avalanche danger is highest in the southern Bitterroot where the layer of buried surface hoar is especially well preserved and has produced multiple skier triggered avalanches and close calls.

 

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.

    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 the upper elevation, have shown no red flags before producing a large avalanche. 

    Where can you find the problem? These distributions are general, but the buried depth hoar can be found primarily at upper elevation on north through east facing slopes. The crust/facet combination is primarily on south aspects at upper elevation but has been found on all aspects and down through mid elevations. Buried near-surface facets exist in the middle of the snowpack on all aspects at upper elevation and southeast through west aspects at mid elevation. Finally, the buried surface hoar can be found on all aspects at the upper elevation and in sheltered areas at mid-elevation.  The distribution of surface hoar as an avalanche problem is often highly spatially variable, and you may find it on one slope but not the next.

    How can you identify and avoid the problem? In short, don't try to outsmart the persistent weak layers right now. It has been a busy week with both natural and human triggered avalanches on all these layers.  With such a complex overlapping web of persistent slab problems, the best way to avoid the avalanche problem is to be patient and understand that we need to give the snowpack time to heal. Use terrain management and slope angle to avoid the persistent slab problem today.

    If you experience cracking or collapsing or see recent avalanches on slopes similar to what you are looking to ski, assume there is at least one, if not more, persistent, weak layers and stick to slopes under 30 degrees.

     

     

    Photo: Cam Mackenzie

  • Loose Wet

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

    With warm temperatures and a lack of solid refreeze last night, wet loose avalanches are likely at low elevations in areas with enough snow depth to produce them. Today, there is potential for greenhousing at mid elevation in areas with full cloud cover and minimal wind. This can heat the snowpack rapidly, leading to widespread wet snow avalanches.

    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. Rollerballs, pinwheels, and small point releases are indicators that the snow is losing strength, and wet, loose avalanches could follow.

    (1/21/2024)

    Numerous wet loose avalanches released yesterday.

    Photo: Payton Schiff

Avalanche Discussion

The past 24 hours did not see any significant weather. Temperatures at upper elevation stayed in the mid 20s through the night, and low elevation temperatures hovered right around freezing. Winds were light out of the southwest. Looking into the weekend, there is potential for warm temperatures and high elevation rain.

Avalanche danger remains considerable at upper elevation due to the reactivity and likelihood of triggering an avalanche. The snowpack is abnormally weak this season, and we need to adjust our decision making accordingly.  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:

Check out the week in review video to see a summary of recent avalanche activity

Large remote triggered avalanche in East Seeley

Snowmobile remote trigger in central Bitterroot

Skier triggered avalanche outside Lost Trail resort

Another skier triggered avalanche outside Lost Trail

A report on the avalanche incident outside of Phillipsburg has been released. Thanks to the Beaverhead-Deerlodge forest for facilitating the investigation.

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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