Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 8 months ago.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

Highlights

Human triggered avalanches are likely anywhere the wind has blown new snow into a slab 6 inches thick or more. Watch for red flags like shooting cracks, blowing snow, or fresh avalanches. If you see these, stick to slopes less than 30 degrees. 

Low elevation (below 5500') at Lolo Pass will have moderate danger due to higher new snow totals and blowing snow. Low elevation danger for the rest of the Bitterroot range outside Lolo Pass is low danger. 

Persistent slab avalanches are possible in the southern Bitterroot and unlikely in the rest of the zone. See the problem description below for more details. 

Avalanche problems

  • Wind Slabs

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

    18 inches of snow has fallen in the central Bitterroot since the 5th, with reports of blowing snow and natural avalanche activity. Elsewhere in the Bitterroot, new snow totals are closer to 12 inches. Triggering a wind slab 1-3 feet deep on wind loaded slopes will be likely today. 

    Wind slabs often form just below ridgelines, below slope convexities, and in cross-loaded gullies. Identify wind slabs by looking for pillow-shaped deposits and wind drifts.  Avoid slopes over 30 degrees if you see signs of instability like recent avalanches, shooting cracks, or blowing snow. 

    (1/7/2026)

    Fresh wind slab in the central Bitterroot just above Bailey Lake. Public ob: Jesse Crocker

    Photo: Jesse Crocker

  • Persistent Slabs

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

    Triggering a larger slab avalanche that fails on small faceted crystals below the uppermost crust remains possible, especially in the southern Bitterroot. Elewhere in the zone, this problem is unlikely. There is some uncertainty about the distribution of this problem, but all slopes over 6500' with a buried crust and 1-3 foot slab above are suspect. No avalanches have been observed on these layers in two weeks, but as it continues to snow, the load on these layers is increasing and may reach a tipping point. 

    In the southern Bitterroot, we have not seen recent avalanches on this layer, but snowpack structure is poor and shows propagation potential in snowpits. 

    You are unlikely to see obvious signs of instability, like cracking or collapsing, before triggering a persistent slab avalanche. To identify areas where the problem exists, dig in the snow and look for weak snow surrounding crusts. If you find this and want to avoid the avalanche problem, stick to slopes less than 30 degrees in slope angle. 

Avalanche Discussion

Although overnight snowfalls were less than forecasted, 48 hr snow totals come in at 1-2 feet of new snow in all zones. Another round of snowfall is expected for the next 24 hr period (5am Thursday - 5am Friday) with 6-13" in the southern Bitterroot, 7-11" in the central Bitterroot, 4-7" in the Rattlesnake, and 6-10" in Seeley. Winds will increase Thursday with the arrival of the storm and another layer of fresh wind slabs is expected to form. 

There is still uncertainty around the persistent slab problem and its distribution. It is unlikely in areas like Lolo Pass where December rain events fully saturated the snowpack. As you move south to areas like the central Bitterroot, it is unlikely in areas like Lost Horse or along the Bitterroot crest where the snowpack is deep. At the same elevation at the mouth of the Bitterroot canyons, the snowpack is much thinner and areas with weak snow around a crust are possible. If you decide to dig in the snow, please let us know what you are finding. Snowpit tests are helpful but not necessary, even a photo of your snowpit wall helps!

On January 5th, a snowmobiler was killed in an avalanche near Lake Tahoe. Our condolenses go out to the family and friends. If we look at the preliminary accident report, we find terrain and wind slab avalanche size that resembles much of the motorized terrain in our forecast zones. We mention this as a reminder and learning opportunity that even short running avalanche paths can be dangerous if they bring you into trees or terrain traps. 

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!

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