Avalanche forecast

Bitterroot

West Central Montana Avalanche Center
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Avalanche danger

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

Large and consequential human triggered avalanches remain possible today at middle and upper elevations. You could trigger an avalanche from gentle slopes adjacent to steeper slopes. Red flags such as cracking, collapsing, and recent avalanches may not be obvious. Dig down, and if you find weak, sugary snow beneath denser, harder snow, stick to slopes under 30 degrees without steep terrain above you.

Avalanche problems

  • Persistent Slabs

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

    Large human-triggered persistent slab avalanches are possible today at middle and upper elevations. A large avalanche is big enough to bury a person and cause fatal injury. There are numerous persistent weak layers buried within the snowpack, including surface hoar, facets, crusts, and depth hoar. Significant snowfall throughout the week has added load to these buried weak layers, creating a poor snowpack structure.

    Poor snowpack structure can be identified by digging down into the snowpack and looking for denser or harder snow sitting above softer, sugary snow. Buried surface hoar can be difficult to identify but often appears as a thin grey line across a snowpit wall. Buried crusts often have soft, sugary snow just above or below them.

    Signs of instability may not be obvious today. These include cracking, collapsing, whumpfing, and recent avalanches. You can trigger an avalanche from a distance (remote triggering), so be aware of the terrain above and around you. If you find poor snowpack structure or signs of instability, stick to low angle slopes and keep a distance from steep slopes above or around you.

  • Wind Slabs

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

    Human-triggered wind slab avalanches are unlikely today at upper elevations. These wind slabs originally formed from a storm on Wednesday that delivered 8-12 inches of new snow. Wind slabs generally heal fairly quickly; however, you can still find reactivity in isolated terrain today.

    Wind slabs often appear rounded and pillowy. They can be found on or just below ridgelines, on saddles, and in cross-loaded gullies. Light snowfall from yesterday may have concealed wind slabs and made them difficult to identify.

    Signs of instability include shooting cracks, collapsing, and recent avalanches. A wind slab avalanche has the ability to step down into buried persistent weak layers and cause a larger and more destructive avalanche. If you see signs of instability, avoid steep, wind loaded slopes.

Avalanche Discussion

Significant snowfall from earlier in the week brought the snowpack to its breaking point. Numerous large human triggered and natural avalanches occurred, some of which were triggered from a distance (remote triggering). While we are now past the point of peak instability, it remains possible to trigger a large and consequential avalanche. 

Decision making under considerable danger requires a conservative mindset. Persistent slabs, true to their name, are persistent and take time to heal. Poor snowpack structure was built from a long stretch of predominantly dry weather at the beginning of the season, followed by more consistent snowfall this month. Weak, sugary snow makes up the base of the snowpack in many areas, and a slab of more consolidated snow sits on top. In some areas, nearly half of the snowpack is made up of weak snow. 

Periods of calmer weather may make it tempting to push boundaries and step out into more committing terrain. Remain vigilant and know that persistent slabs will take time, patience, and self-control to manage. It is crucial that you resist the urge and opt for low-angle skiing and sledding while we give the snowpack the time it needs to strengthen.

This blog post from the Utah Avalanche Center may be helpful in explaining the avalanche danger for today and why avalanche conditions are complicated and dangerous. Current snowpack conditions put your relative risk on the low end of the considerable rating today.

A ridge of high pressure will bring increasing temperatures and possible rain at lower elevations. Due to sustained cloud coverage, it is unlikely that the snow will be impacted by warm temperatures. There is a small possibility of encountering wet loose avalanches in lower elevations where rain may fall, but the likelihood is quite low.

Possible rain on snow will not help with thin conditions at lower elevations. Continue to keep an eye out for ground hazards such as downed logs, stumps, and rocks. They may exist under recent snow and be obscured from view.

Light snowfall is forecasted for tonight, favoring the northern end of our forecast region with light wind out of the south and southwest. 

Please submit an observation of what you’re seeing out in the backcountry. Reports of avalanche occurrences, weather conditions, and snowpack observations are all very helpful for the forecast team.

Ski and ride safe!

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