Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
View on map

Avalanche danger

Fri
Alpine
2 · Moderate
Treeline
1 · Low
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Out of date — this forecast expired 8 months ago.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 remain possible at upper elevations on north through east aspects, where slopes were previously wind-loaded.

Buried weak layers around crusts pose a low likelihood, high consequence persistent slab problem. You may not see red flags before an avalanche occurs on these layers. To identify the problem you have to dig down and look for it. If you find weak snow surrounding crusts, avoid avalanches by sticking to slopes less than 30 degrees.

Avalanche problems

  • Wind Slabs

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

    Wind slabs up to a foot deep still linger at upper elevations on north through east aspects. Continued natural avalanches are unlikely, but human-triggering a wind slab avalanche is possible.

    You are most likely to find wind slabs on the downwind sides of ridges and roll-overs. Look for relatively hard pillow-shaped deposits. Wind slabs often form immediately below cornices, which is where we saw a number of natural avalanches last weekend.

    You can avoid this problem by avoiding slopes over 30 degrees where you see obvious drifting, feel “upside-down” snow underfoot, or find strong over weak layering in the surface snow.

    If you choose to enter avalanche terrain, reduce potential consequences by avoiding terrain traps such as gullies, cliffs, and trees. Always expose only one person at a time.

    (12/31/2025)

    The crowns from two older wind slab avalanches on Point 6. These are on an east aspect, and likely occurred naturally on December 27th.

     

  • Persistent Slabs

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

    This is a classic low-likelihood high-consequence avalanche problem.

    Weak sugary facets surrounding crusts are buried two to four feet deep. This facet crust combination was formed by rain and fluctuating freezing levels in mid to late December.

    We have not seen recent persistent slab avalanches, but this layer has been reactive in snowpack tests. Triggering a persistent slab avalanche right now would likely take a large load such as a cornice fall, or bad luck by finding a place where the weak layer is sensitive and the overlying slab is thin.

    The highest elevation north-facing slopes have additional weak snow near the ground. This snow is gaining strength, but could be triggered in isolated areas by a very large load.

    You are unlikely to see obvious signs of instability, like cracking or collapsing, before triggering a persistent slab avalanche. Dig down and look for weak layers surrounding crusts. If you find strong snow over weak snow, consider staying off of slopes over 30 degrees.

    (12/31/2025)

    Snowpit on a north aspect at 6800 ft in the Bitterroot, with multiple layers of crusts and facets.

Avalanche Discussion

While the likelihood of triggering an avalanche is decreasing, the consequences may be significant, thanks to buried persistent weak layers. Triggering these layers will likely require a large load, such as a cornice fall or a surface avalanche. Last weekend’s storm left us with cornices and surface wind slabs, both of which could be triggered by a human or snowmobile, and could step down to a buried weak layer.

Wind slab avalanches are dangerous in their own right, so don’t discount them, even as they become less sensitive to triggering. We are still seeing propagation on this wind slab in snowpack tests, and have heard of snowmobiles triggering small wind slabs in the Seeley Lake area.

Yesterday we noticed surface warming on southerly slopes. Thanks to the temperature inversion, warming has been most pronounced at high elevations. Warming yesterday only penetrated the first few inches of snow, and roller balls got hung up on soft snow underneath before they could produce even small wet loose avalanches. If roller balls entrain enough snow to become point releases, or you find yourself sinking into wet unsupportable snow, it is time to move away from sunny slopes.

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.

Regions covered