Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Wet avalanches may run in newer snow layers as the sun shines intensely onto steep slopes facing the sun, so limit your exposure to these slopes if you see rollerballs or wet avalanches. Increasing wind will likely redistribute any loose, dry, snow, especially at upper elevations. Search for actively blowing snow or drifted slopes, and avoid traveling in steep terrain with these newly formed drifts.  

We'll probably only get a trace of new snow, but temperatures will be warmer and we'll see more sun.

You might encounter either wet or dry avalanche problems based on the amount of new snow you find and how warm it gets. Keep an eye on evolving conditions throughout the day. Test the bond of new snow layers before heading into steeper terrain. Limit your exposure to steep slopes where you witness fresh rollerballs or other signs of instability. 

Avalanche problems

  • Loose Wet

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

    Snow may have initially been affected by the sun on Saturday, but Sunday will be warmer and sunnier. More wet loose avalanche activity could result. We expect a crust to form Saturday night on any previously wet snow surfaces. A thin crust above the new snow layer on sunny aspects could break down and get wet, with resulting avalanches in the wet snow. If you notice wet, sticky snow or already see rollerballs or slides, avoid similar steep slopes and terrain beneath them. 

    Don't linger directly under cornices, snowy cliffs, or glide cracks lurking in the terrain above you. The likelihood of seeing additional wet avalanche activity or cornice falls since our large period of rain and warm temperatures is low but not completely out of the question. 

    Example photo: Roller balls and small blobs of snow shedding off rocks are indicators that wet loose avalanches may occur next. 

  • Wind Slabs

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

    Increasing winds will develop new wind slabs on Sunday. New snow above our most recent atmospheric river crust varies from a few inches to around a foot, depending on elevation and location in the forecast zone. As you gain elevation, you'll find a thicker snow layer and deeper drifts. These drifts, even if small, may sit over a crust that they could slide easily on. 

    Search for actively blowing snow and rippled or smooth, pillowlike surfaces. If you find new drifts and the snow layer is nearing 6 inches or more over the crust, then steer around steep slopes. Since most new wind slabs will probably be shallower, you can do simple tests to help identify how easily these new slabs run. Although we don't expect this to be the case, non-wind-affected layers may still slide over the crust. 

    Example photo: Here, a very small human-triggered wind slab failed over a crust. You may see similar conditions on Sunday. Maybe this one was inconsequential, but if they get larger they could be a problem. 

Avalanche Discussion

The West North, Stevens Pass, and Snoqualmie zones each reported a large unusual avalanche that occurred Friday night. These appear to all probably be residual wet avalanches from our lingering warm temperatures and rain. Nonetheless, there were no reports of either larger natural avalanches or human triggered avalanches in neighboring zones by publish time Saturday. 

Overall, observations have been quieter lately throughout the Cascades. In general, wet snow avalanche problems from the past week are diminishing as temperatures cool and there is less free-running water to weaken the snowpack. We expect the best freeze since the warming event on Saturday night, so the old crust will freeze more for Sunday. 

There is probably about 6 inches to a foot of snow over the old melt layer and crust. On Friday in neighboring zone, the new snow was observed to have a poor bond to the old snow surface, and small wet loose avalanches were easy to trigger. It appears that the bond improved for Saturday.

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