Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Saturday looks like a gorgeous day in the mountains. However, the swing from this week’s snow to warm and sunny weather could cause some slopes to start to slide on their own. Pay attention to the areas above you and limit the amount of time you spend on and under steep terrain once you notice the surface becoming wet and sticky.

Avalanche problems

  • Loose Wet

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

    With Saturday's warm and sunny weather, you’ll undoubtedly see natural loose wet avalanches, especially near trees and rocks. A few of these slides could even grow rather large. However, gradually warming temperatures and brief periods of sunshine should help limit the size and number of avalanches in this cycle. A good overnight freeze also means the sun will need to break down a new crust before you worry about these wet slides. This could happen faster on sunny slopes above you, than down in cooler shadier valleys. Watch for rollerballs, snow falling off trees, and fan-shaped debris to let you know the surface is becoming wet and unstable. Then, limit the amount of time you spend on and under similar slopes. 

    Even though loose wet avalanches will be the most common problem, weather patterns like this often lead to worry that the mountains will start to “shed.” While we expect that to be a greater issue on Sunday, you could see an isolated event Saturday. Blocks of snow may fall from rocks, cornices could collapse, and loose wet slides might gouge into older snow layers. Pay attention to the terrain above you, and don’t linger underneath large steep slopes, rocky terrain, and looming cornices.

    (3/24/2022)

    Example: Rollerballs, loose wet slides, and collapsing cornices from a warm sunny period earlier this winter. Mt St Helens. 

    Photo: Andrew Kiefer

  • Wind Slabs

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

    At this point wind slabs are a few days old, becoming hard to find, and maybe even harder to trigger. However, if you use the sunny weather to head up into the alpine, keep this problem on your mind. Variable winds formed drifts on nearly every aspect this week. So, you could see slabs in locations normally stripped of snow. Look for and avoid pillow-like drifts, especially in high-consequence terrain.

    (4/11/2022) Example: Wind slabs forming on some unusual aspects earlier this winter.  Photo: Dallas Glass

Avalanche Discussion

Recent snow, sunshine, and warm temperatures will make the mountains look quite inviting this weekend. Even though we aren’t talking about widespread avalanches or dangerous conditions, you will probably see natural slides. If avalanches become larger and more widespread than anticipated, it’s time to get out of their way. This could include many cornices collapsing, rocky faces shedding their snow, or avalanches involving deeper layers in the snowpack. Any of these events would mark a shift towards much more hazardous conditions. 

An active weather pattern brought near-daily snowfall to the West South zone this week. Sun breaks between showers added thin crusts between layers of storm snow on some slopes. This includes a new surface crust that likely formed from the sunshine on Friday. All total, most locations received 12-18” of snow since 4/18. This is the snow we’re primarily worried about on Satruday. However, while we aren’t expecting deeper avalanches yet, we have our eye on all the snow above the widespread and prominent 4/8 crust. You can find this layer 3-4 ft below the surface. If we enter a true shed-cycle, avalanches could involve some or all of the snow above this layer.

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