Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 2 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avalanche activity is expected to slow a little as we are in a cooling trend. Large, dangerous avalanches remain possible, even if they are a little less likely than previous days. Consider continuing to avoid terrain beneath corniced slopes or rocky steeps and glide cracks with large snow deposits still intact until temperatures further cool. 

Avalanche problems

  • Glide Cracks

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

    You probably won't see any signs of instability until a large avalanche releases beneath a glide crack. There's a good chance you'll see an overhead glide crack warning you of impending danger, though. Limit your exposure to steep terrain and the lower angle slopes beneath them, especially where you see cracks or wrinkles in the snow that indicate where the entire snowpack is slipping on a smooth ground surface. Blocks of melting snow clinging to rock faces are also a red flag.

    After days of hot weather, we suspect most avalanches have already happened.  However, glide activity lingers even as temperatures begin to cool, since water may still be percolating down through the snowpack. While many slopes have shed wet snow, natural loose snow avalanches can still be triggered by cornice fall or snow shedding from rocks and cliffs.

    Example photo from earlier this year: A glide crack and wet avalanche debris on a northeast facing slope near Welcome Pass. Avoid traveling beneath glide cracks, as they could fail and avalanche without warning. 

  • Cornices

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

    Infrequent large cornices began peeling off over the weekend. A large cornice fall on Monday in the Baker backcountry triggered a large slab avalanche on the slope beneath it. We suspect large cornices are peeling off all over the West North zone, and some are triggering large, unsurvivable avalanches on the steep slopes beneath.

    The slight cooling may slow activity a bit, but not enough to make us feel good about traveling beneath cornices yet. Identification and travel advice for this problem is simple - don’t travel under cornices until there is a significant drop in temperatures for a few days. Stay well away from steep slopes below cornices as well.

    (3/18/2024)

    Large cornice fall and slab avalanche on a north aspect at 5000' in the Baker BC. Arrow shows the cornice that shed a huge chunk onto the slope below. Plenty of cornice remains.

    Photo: Mt. Baker Ski Patrol

Avalanche Discussion

THIS observer from Monday on Ruby Mtn said they witnessed a large cornice fall, yet it didn't trigger a large avalanche on the slope beneath it. They did a great job of explaining the variability in snow surfaces they found, from crusty to wet to dry and avalanche activity or lack thereof.  We really appreciate the observation!

With most avalanche activity at the moment you won't get any warning signs until a large avalanche starts coming towards. Clues like wet loose avalanches aren't good indicators right now. Freezing levels are cooling a bit for Wednesday. and there's a small uptick in southwesterly wind. For the first time in days, we can expect some cloud cover. There are a lot of variables so we're not quite sure how conditions will change, but we expect snow to be different than the previous days when we had clear skies. Northerly aspects may moisten more than they have previously, and you may see more avalanche activity on those slopes.  Surfaces will probably be stickier.  Temperatures are still warm enough that we don't particularly expect a surface crust to persist for the day, but who knows? 

There's a tiny chance that dry pockets of snow exist at higher elevations on steep, northerly aspects. These may have formed into small wind slabs that could react to a human trigger. If you're in high-consequence terrain, like areas with rocks, trees, or cliffs below you, beware of the consequences of getting caught in even a very small avalanche, where even getting knocked off your feet could kill you.

Pockets of buried surface hoar that have a very small chance of reacting to human triggers may still be found in small, isolated locations on the northerly half of the compass. With several days of warm temperatures, even the surface hoar has been observed as rounding and becoming less reactive. Nevertheless, steep north-facing slopes that haven't seen much sun have stayed cooler and wetting isn't very deep thanks to long-wave radiation losses with clear skies. On southerly aspects, the upper snowpack is melt-affected with alternating layers of moist rounded grains, and wet melt forms down to a crust with water pooling above it. Snow heights at Heather Meadows went from 132 inches at our last snowfall on 3/13 to 97 inches as of 3/19. We've lost almost 3 feet at this location in our week of heat. 

If you're out in the snow, share your observations with us and your local backcountry community. This is even more valuable now that we're getting into the spring and folks are getting out on mountaineering and more distant objectives in the longer daylight hours. Sharing details from areas that are less frequently traveled are even more valuable to help keep the community informed. 

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