Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
View on map

Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
Open full map
Out of date — this forecast expired 8 months ago. You’re viewing past conditions, not the current bulletin.

Highlights

Human triggered avalanches are likely in areas where new snow and wind has built slabs 6 inches thick or deeper.  Identify the wind slab problem by looking for blowing snow, shooting cracks, and fresh avalanches. If you see any of these, stay off slopes over 30 degrees.

 Larger avalanches that fail on weak snow surrounding buried crusts are possible. To identify the buried crust/facet layer, dig in the snow and look for weak or sugary snow above and below a crust layer.

Avalanche problems

  • Wind Slabs

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

    24 hour winds have shifted from the east, to the southwest, to the northwest and during this period they increased in speed to a very strong west/northwest wind. Combined with the 6-12 inches of new snow that fell overnight, reactive wind slabs are likely today, especially on east aspects.

    Wind slabs can be identified by their smooth or pillow like appearance and often form just below ridgelines, in gullies, and below convex rollovers. If you see signs of instability like recent avalanches or cracking around your skis or sled, stick to low angle slopes less than 30 degrees.

     

    (12/24/2025)

    A small intentionally triggered wind slab on an upper elevation northeast aspect

    Photo: Arden Feldman

  • Persistent Slabs

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

    Larger avalanches failing 2-4 feet deep on weak snow surrounding crusts are possible. Multiple snowpits across the Rattlesnake and Bitterroot have shown poor snowpack structure with reactivity and full propagation in snowpit tests. We have not seen any avalanches reported on this layer yet, but all the ingredients for a larger avalanche are present. As more storms continue to load this layer with increasing weight, we could see conditions spike and avalanches become more widespread on this layer. 

    This layer formed during the mid December rain events that were followed by cold snow. At the boundary between warm wet snow and cold new snow, weak snow developed directly above and below a crust. This problem can be highly elevation dependent, but be suspicious of any slope above 6500’ with a buried crust in the snowpack. 

    At the highest elevation north facing slopes, above the rain line from the warm December storms, there is still some weak snow near the ground (depth hoar). This snow is showing signs of rounding or gaining strength but in specific terrain, very large avalanches failing at the ground are possible. 

    Whumfing and collapsing are red flags for persistent weak layers, but you may not see any signs of instability before triggering an avalanche on these layers.  Dig in the snow and look for poor snowpack structure with a slab above a weak, sugary layer. Manage the problem with slope angle and stick to slopes less than 30 degrees. Keep in mind that persistent slabs could also be triggered remotely, or smaller avalanches can step down and trigger a larger persistent slab avalanche. 

    2-3 foot slab sitting above a crust/facet combination. 

Avalanche Discussion

24 hour snow totals are as follows. Keep in mind some of these stations are not at upper elevation and it is likely new snow totals are deeper. 

North Fork Jocko: 6” snow with .4” SWE (snow water equivalent)

Rattlesnake: 5” snow with .5” SWE

Lolo Pass: 6” snow with .5” SWE

Twin Lakes: 9” snow with .9” SWE

Saddle Mountain: 2” snow with .3” SWE

While at first glance, overnight snow totals don’t live up to the forecast, if we take these mid elevation SWE numbers and make estimations for upper elevation, we can expect 8-12 inches of new snow overnight.  Moving forward, we are trending toward cooler and drier conditions as a ridge of high pressure enters the region into next week. 

Most of the avalanche danger today will be a direct result of the new snow and wind. This instability will be short lived, and will become less reactive within 24 hours. If you are out in the mountains today and seeing red flags or avalanches, be patient and give the new snow time to settle out. 

The persistent slab problem will likely be with us for a while. It will take time for rounding to occur and the snowpack to gain strength around the buried crust. This problem deserves respect, even if it is not producing avalanches right now. Many avalanche accidents are a result of avalanches failing on weak snow surrounding crusts. 

The WCMAC team is excited to be back to issuing full avalanche forecasts. Avalanche forecasts will be issued on Thursdays, Fridays, Saturdays, and Sundays. A general information product will be issued on Mondays to cover the Monday-Wednesday period. We hope to begin forecasting for the Seeley Lake zone next week. Thank you for your patience while we worked through our agreement with the Forest Service! 

Let us know what you see by submitting an observation. We appreciate all observations, no matter how small, as our forecast area is large, and it helps us understand conditions across all zones. 

Ski and ride safe.

Regions covered