Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
1 · Low
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Highlights

Large human triggered avalanches are likely at middle and upper elevations today. The avalanche danger will rise throughout the day as rain falls up to upper elevations, increasing the sensitivity of our already unstable snowpack. Look for red flags like recent avalanches, cracking, collapsing, rain on snow, or rollerballs. If you encounter any of these, or find a poor snowpack structure with a firm slab over weak, sugary snow, stick to low angle slopes without steep terrain above. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    Large and consequential persistent slab avalanches are likely today at middle and upper elevations. The avalanche danger will rise throughout the day as temperatures increase and rain falls up to around 7000 feet. The rain will decrease the strength of the snowpack and increase the likelihood of triggering an avalanche. Natural avalanches will become possible, especially this afternoon and evening, when the precipitation is strongest. 

    A variety of overlapping buried weak layers, including surface hoar, facets, crusts, and depth hoar exist on all aspects at middle and upper elevations. You can recognize persistent weak layers and poor snowpack structure by digging into the snowpack and looking for a dense slab on top of weak, sugary snow. Buried surface hoar can be more difficult to identify in a snowpit but it often appears as a thin horizontal line across the snowpit wall face. Some layers, like the buried surface hoar, have produced obvious red flags and widespread collapsing. Others, like the depth hoar at upper elevations, have shown no red flags before producing large avalanches. 

    Don't try to outsmart the persistent weak layers right now. It has been a busy week with both natural and human-triggered avalanches on all these layers. Today’s rain will increase their sensitivity again. Red flags include whumpfing, collapsing, shooting cracks, and recent avalanches.  If you find poor snowpack structure, signs of instability, or rain on snow, stick to low angle slopes. Be aware of the terrain above and around you, as you can trigger an avalanche from a distance (remote triggering).

    (1/26/2024)

    A large slab avalanche on an east aspect at 7400 ft in Jenny Bowl near Point 6 in the Rattlesnake. It likely failed during the warm temperatures last weekend (1/20/24 or 1/21/24). 

    Photo: Arden Feldman

  • Loose Wet

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

    With increasing temperatures and rain forecast up to 7000 feet today, wet loose avalanches will become likely. If you sink into a wet snow surface or experience rain on snow, expect wet snow avalanches in steeper terrain. Rollerballs, pinwheels, and small point releases are indicators that the snow is losing strength, and wet loose avalanches could follow. Even a small avalanche can be consequential if it pushes you into rocks, trees, or terrain traps like streambeds and gullies. In areas where buried persistent weak layers exist, rollerballs and wet loose avalanches could step down and trigger larger persistent slab avalanches. 

    (1/21/2024)

    Numerous wet loose avalanches released yesterday.

    Photo: Payton Schiff

Avalanche Discussion

Today, an atmospheric river will begin impacting the region. We can expect periodic precipitation to increase throughout the day and rain/snow levels to increase to around 7000 feet by this afternoon. There is some uncertainty in the forecast, and if the rain decides to hold off until this evening, then the sensitivity of our avalanche problems may only increase tonight and tomorrow. 

Rain on a dry snowpack is a significant red flag. It decreases the strength of the snowpack and can create complicated and dangerous avalanche conditions. This, combined with our already abnormally weak and dangerous snowpack, should be more than enough reason to keep things mellow today. Multiple close calls in the past week involving large human-triggered avalanches reinforce the need to dial back terrain choices and stick to low angle slopes. Check out the observations page and the week in review video for more information about the numerous recent avalanches. 

The avalanche danger is highest in the Southern Bitterroot where a layer of buried surface hoar is especially well preserved and has produced several skier triggered avalanches and close calls. 

A report on the avalanche incident outside of Phillipsburg has been released. Thanks to the Beaverhead-Deerlodge forest for facilitating the investigation.

Please continue to submit observations. We appreciate every observation we get, and it really does help us get a better understanding of what is happening across the forecast area. 

Ski and ride safe.

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