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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Highlights

Warm temperatures and direct sun will create dangerous avalanche conditions today. Large human triggered wet loose avalanches are likely on south and west aspects at all elevations. Signs of instability include rollerballs, unsupportable wet surface snow, and snow falling out of trees. You can still trigger a large persistent slab avalanche at upper elevations. You are unlikely to see signs of instability, such as cracking and collapsing, before triggering. Ridgelines and slopes less than 30 degrees will be your safest options today.

Avalanche problems

  • Loose Wet

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

    Large human triggered wet loose avalanches will become likely on sun affected slopes today. Cloud coverage will be minimal throughout the day, and temperatures are expected to be warm, possibly reaching the high 40s (F) at upper elevations. The wind will be very light which will add to the warming trend.

    Many previously solar-affected areas have a surface melt freeze crust after warm weather yesterday and a refreeze overnight. Today, that crust must break down before the snow can lose strength and lead to wet loose avalanches. If you find yourself in an area with strong sun holding fresh, dry snow, expect the snow to become wet more quickly. Steep slopes that are directly exposed to the sun will be the first to manifest this problem. Fresh rollerballs/pinwheels or snow falling out of the trees are your first clue that the surface snow is changing.

    Small point releases can entrain large amounts of snow and travel further than expected. While slow-moving, an avalanche of this nature will be hard to escape and could easily push you over cliffs or into trees. If you find yourself in wet, unsupportable snow or see natural, wet loose avalanches, mark that as the time to step back out of avalanche terrain. A sluff of wet snow can step down and trigger a larger persistent slab avalanche in areas with poor snowpack structure, creating a more consequential avalanche. Limit your risk by choosing slopes that are more shaded and/or less steep. 

    (3/14/2024)

    Rollerballs/pinwheels on south and southeast aspects indicate that a larger and more consequential wet loose avalanche will likely follow.

    Photo: Payton Schiff

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1.5–2.5

    Although unlikely, you could still trigger a large persistent slab avalanche on all upper elevation aspects today. Various persistent weak layers are buried in the snowpack, with the most concerning layer being facets above a melt freeze crust midway down. You can identify this combo by digging 2-4 feet down until you find a stout crust.

    Warming today could cause persistent weak layers to lose strength if liquid water enters the snowpack. Weak layering is more pronounced on shadier and colder slopes. You will most likely trigger a persistent slab avalanche on convexities, rollovers, or near rock bands. Before triggering, you will unlikely see obvious signs of instability, such as cracking and collapsing. Snowpit tests are unlikely to yield unstable results. Smaller wet loose avalanches can step down and trigger a larger avalanche on persistent weak layers. Large cornices that have developed over the last several weeks that sag and fall onto the slope below due to warming could also be a likely trigger.

    Recognize the continued potential for large and dangerous persistent slab avalanches. Use your individual or group risk tolerance to dictate how steep of a slope you are willing to expose yourself to. You can reduce your risk by defaulting to shorter, planar slopes without convexities or rollovers and with runouts free of surface obstacles and terrain traps. Reduce your time spent in paths with large cornices looming above. Use slope angle to avoid the problem altogether by sticking to slopes less than 30 degrees.

    (3/14/2024)

    Poor snowpack structure remains at upper elevations. Dig 2-4 ft down to find facets above a stout crust.

    Photo: Payton Schiff

Avalanche Discussion

Managing wet snow and lingering persistent weak layers will make for some "catch-22" decision making today. The snow on sunny slopes will be hard and crusted over in the morning before quickly turning wet and sticky by the afternoon. After what will surely be a perfectly timed corn snow lap, we will likely move to more polar aspects where the snow has remained soft and dry. These aspects harbor more pronounced weak layering, and the potential for a persistent slab avalanche is higher. As the snow gets more affected by warm spring weather, we will all be driven to skiing and sledding slopes that maintain the precise recipe for large slab avalanches. Keep this in mind as the winter season wanes, but poor snowpack structure remains. 

Cornice fall will be a growing concern as springtime weather prevails. Cornices will weaken due to sun and warm temperatures. Limit your time spent underneath these hazards and stay well back from the edge while traveling along ridgelines.

An avalanche fatality occurred on Tuesday, March 12th, in the southern Bitterroot. You can view the preliminary accident report here. A full report will be issued within the next 30 days. Our deepest condolences go out to the family, friends, and community affected by this tragic event.

Please let us know what you're seeing out in the backcountry by submitting an observation. As we cannot be everywhere all the time, community reports of weather, stable or unstable snowpack conditions, and avalanches are essential information for us.

Ski and sled safe!

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