Bulletin d’avalanche

West Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Points saillants

Very dangerous avalanche conditions are present at this time. Natural avalanches are likely, and human triggered avalanches are very likely while massive amounts of snow continue to pummel the area. Stay out of avalanche terrain, including low angle slopes beneath avalanche paths while the storm runs its course. 

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    2–3

    We are in the midst of a major storm cycle, the time when avalanches are most likely to occur. There have been numerous reports of natural and human triggered slab avalanches up to size 2 in the last 3 days.  Failures are happening on interfaces within the new snow layers, and some avalanches have failed all the way down to the 12/21 crust. By Saturday at least 4 feet of snow will cover this crust at upper elevations.

    Winds will remain strong through Saturday, contributing to thicker and more reactive slabs on leeward slopes, especially as you gain elevation.  Regardless, this much snow calls for travelling with extreme caution, and steering clear of all avalanche terrain including the runouts beneath steep slopes.  

    Human triggered slab avalanche on a NE aspect at 4900ft on Thursday in the West North Zone. Photo: Jake Little

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Wet loose avalanches occurred Friday as rain fell on the snow surface. These avalanches remain likely as snowline hovers around 4000-5000ft for much of this storm. Rollerballs coming off steep slopes are your first indicators that the snow surface is losing its strength, and wet loose avalanches may follow. Steer clear of steep lower elevation areas with clues that the wet surface could avalanche. Keep in mind that extensive rain could awaken glide avalanches, another avalanche problem to avoid on steep slopes.

    Rollerballs! Clues like this indicate the surface snow is becoming wet and unstable. Photo: NPS rangers

Avalanche Discussion

Over 4 inches of water fell since Wednesday, and at least another 3 inches will fall by the end of the day on Saturday. Above 5000ft most water fell as snow, while Friday was a wet day with the snowpack shrinking at lower elevations. This much snow leads to very dangerous avalanche conditions, and a lot of uncertainty in regards to where and when failures will happen. The busy holiday period ends this weekend but avalanches won’t go on hold for your last bit of holiday fun. Stick to low angle lines to finish up your holiday safely. 

Be aware of avalanche paths that cross roads and trails, as there are many in the area.  Snow is quickly building so avalanches will have a higher likelihood of hitting the routes- even if where you are has little to no snow cover. Do not linger in areas with distinctly thinner or smaller trees, especially if they look thinned for as far as you can see uphill, which could indicate an avalanche path crossing your travel route. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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