Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Highlights

Large avalanches 1.5 to 2.5 feet deep, failing on weak snow above a crust, are possible at upper elevations today. Skiers and riders could also trigger wind slabs on all aspects at upper elevations due to shifting winds. Cracking and collapsing will alert you to wind slabs but may not be obvious before triggering a deeper weak layer. You can use slope angle to avoid the problems entirely by sticking to slopes under 30 degrees. 

Avalanche problems

  • Persistent Slabs

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

    Large persistent slab avalanches are possible on upper elevation slopes facing west, north, and east. A slab of recent snow 1.5 to 2.5 feet deep rests on a weak layer of small facets above a crust on some upper elevation slopes. This was the weak layer in a large, widely propagating skier triggered avalanche in the Seeley Lake zone on Thursday. 

    You may not experience signs of instability like collapsing or whumpfing before you trigger an avalanche on this layer. If you do see signs of instability, stick to lower angle slopes. You can identify the problem by digging in the snowpack and looking for a layer of weak snow just below the recent storm snow and above a stout crust. However, the weak structure may be difficult to identify because the faceted snow crystals are small. 

    There are also still areas with weak faceted snow buried near the ground. It has been over two weeks since the last avalanche on these deeper layers, but the poor snowpack structure remains. You are unlikely to trigger one of these deeper layers, but a persistent slab avalanche in the upper snowpack could step down and break out a much deeper avalanche. 

    You can use slope angle to avoid the problem completely by sticking to slopes under 30 degrees. Short of that, you can reduce your risk by avoiding large avalanche paths and those with ugly consequences if you are caught in a slide.  

    (2/16/2024)

    Taking a look at the crown of a skier triggered avalanche from yesterday on the west side of the Seeley Lake zone. 

    Photo: Arden Feldman

  • Wind Slabs

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

    Due to shifting winds, skiers and riders could trigger wind slabs on all aspects at upper elevations today. Over the last several days, south and east winds drifted snow into wind slabs on north and west facing slopes. Today, light snowfall combined with increasing winds shifting back to southwest and west will build new slabs on north and east aspects. 

    Wind slabs often form along ridgelines, in gullies, around rocks, and on convex rollovers. Due to previous east winds, you could encounter old wind slabs lingering in terrain opposite where you usually find them. 

    Wind slabs can often be identified by their smooth, rounded appearance. If the snow feels hollow under you, this is also a good indicator of wind slab. Avoid the problem by sticking to sheltered or wind scoured areas.  If you encounter sensitive wind slabs or are seeing red flags like cracking and collapsing, stick to slopes under 30 degrees. 

    (2/15/2024)

    Small intentionally triggered wind slab on an upper elevation west aspect. 

    Photo: Arden Feldman

Avalanche Discussion

After two days of wonderful sunshine, a weak storm system will impact the region today. Snowfall totals will be light, up to a couple of inches, and winds will shift to southwest and west. 

Yesterday, strong east winds impacted the southern Bitterroot, and observers reported fresh wind slabs in unusual locations. Observers also reported south winds and a small fresh wind slab on an upper elevation northeast aspect in the central Bitterroot. With winds continuing to shift today, stay alert for new and old wind slabs on all aspects at upper elevations. If today's snowfall overproduces, the new wind slabs could become touchy. 

Small dry loose avalanches are possible in very steep north facing terrain where loose, low density surface snow exists. If you are considering entering that type of terrain, be prepared to manage your sluff, and consider the consequences of even a small slide. 

Yesterday, we transitioned the storm slab avalanche problem to a persistent slab avalanche problem across the region. The recent snowfall rests on a layer of small facets above a crust on some upper elevation slopes. This means that the problem has not fully stabilized yet. We need to remain cautious and shift to a persistent slab mindset to manage it. The close call on Thursday with a large, widely propagating persistent slab avalanche in the Seeley Lake zone reinforces this idea. The group reported that they did not experience any signs of instability before triggering the avalanche. They also dug a snowpit beforehand, and their extended column test was unreactive. 

The distribution of the new persistent slab problem at upper elevations is still uncertain. Today, we removed the problem from south and southwest aspects due to the last two days of sunshine and surface melting on those aspects. We have limited information on how widespread the problem is on other aspects. The most suspect areas are where the recent snow forms a deeper or stiffer slab. The simplest way to manage the problem is to stick to low angle slopes. 

Let us know what you see out there this weekend by submitting an observation. Even reports of stable avalanche conditions are useful. 

Ski and ride safe.

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