Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 6 months ago. You’re viewing past conditions, not the current bulletin.

Highlights

It remains possible to trigger an avalanche on weak layers buried 1-3 feet deep. Potential triggering locations are difficult to predict, and any slides on this layer will be large and destructive. It is also possible to trigger a new snow avalanche in wind-loaded places. Watch out for this in steep open areas exposed to the wind. Avalanches that start in the new snow may break down to those buried weak layers.

The elevated hazard at low elevations focuses on the Lolo Pass area.  Elsewhere, low elevations are at Low Hazard. The Moderate Hazard level will be especially important if the sun comes out and warms the new snow.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Prominent weak layers are buried in the upper 1-3 feet of the snowpack. Yesterday a skier triggered a large avalanche in the Southern Bitterroot (click here for information). These weak layers exist throughout the  Bitterroot Range, and you could expect to see similar avalanches if you find the right place to trigger one. Last week we saw evidence of a widespread natural cycle on persistent weak layers across all three regions.

    Avalanches on these layers are becoming more difficult to trigger as weak layers adjust to their new load and the slab above them thickens. Conversely, this means any avalanche you do trigger will be large - something you do not want to be caught in. We’ve reached a point where we aren’t seeing warning signs of instability, such as collapsing, so triggering an avalanche could be the first sign of instability that you see.

    It is difficult to determine where exactly these avalanches may occur, and where on a slope you’ll find a trigger point. We are getting our weakest stability test results on northerly slopes, and most of last week’s natural avalanches occurred on northeast, east, and southeast aspects. But, a variety of buried weak layers including surface hoar, facets, and crusts have been found in snowpits on all aspects at middle and upper elevations. It seems these layers are most sensitive at the south end of the Bitterroot range, where the snowpack is thinner. It is possible to remotely-trigger these avalanches from below, beside, or above steep slopes. So, completely avoiding this problem includes avoiding terrain threatened from above.

    This very large avalanche occurred naturally on a high elevation NE aspect. If you look closely you can see that the crown continues all the way across the slope under the cliff bands.

     

    (2/28/2026) Photo: Ben VandenBos

  • Wind Slabs

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

    The closer you get to the Bitterroot crest, the more new snow you’ll find. Yesterday we found about a foot of new snow at the head of Lost Horse (Click here for the observation). Commonly skied areas on the east side of the range (including Lost Trail) have closer to a half foot of new snow. Regardless of snowfall amount, it fell with gusty westerly winds, and winds are forecast to continue today. You are most likely to trigger a new snow avalanche in recently wind loaded areas.

    Look for wind slabs near ridgelines and features like gullies that slow the wind down and force it to drop the snow it is carrying. If you find a localized area of relatively deeper or denser snow, you’ve likely found a wind slab. Shooting cracks under your feet or snowmobile are further indications of unstable snow. To avoid this problem, stay off of steep slopes where you see these signs of wind loading.

    Avalanche in steep, wind-loaded terrain in the Bitterroot Mountains. 

    (2/28/2026) Photo: Ben VandenBos

Avalanche Discussion

Avalanche hazard has begun to drop as we move away from Wednesday’s initial loading event. However, not all moderate hazard days are created equal, and we’re currently at the higher end of moderate. This is particularly true for the Rattlesnake region where we saw the highest amounts of new snow. While you’re less likely to see natural avalanches today than you were a few days ago, human-triggered avalanches are still possible. In isolated areas these avalanches could be large thanks to buried weak layers in the snowpack.

With new snowfall it’s easy to focus on what we can see on the surface, but don't forget about what's below. If you dig down, you'll find some combination of crusts, facets, and surface hoar buried 1-3 feet. When dealing with a persistent weak layer avalanche problem, it's good practice to allow the potential consequences of a large avalanche to guide decision-making. We are only a week out from a widespread avalanche cycle, and a close-call yesterday reminds us that triggering a persistent slab avalanche is a real possibility. We are very grateful to the group that shared the information, and are glad they didn't have a worse outcome. Click here to see details.

While moving through the mountains, look for and avoid freshly wind-loaded slopes.  Any wind slab you trigger will be dangerous in its own right, but could also step down to buried weak layers, producing a much larger slide.  If the forecast cloud cover doesn’t appear, keep an eye out for wet snow. Low-density new snow can become wet and lose cohesion quickly. Both of these avalanche problems will be more prevalent where you find deeper storm snow.

If you get out, please continue to send us observations. We appreciate each and every one of them. Information on avalanches you've seen or triggered is bulls-eye information. Click here for our observation form. You can fill out as much or as little of the form as you like.

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