Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Ongoing wind and light snow will make it easy to trigger large avalanches near and above treeline. Use extra caution on slopes over 35 degrees where the wind has drifted recent snow into deeper slabs. If the new snow slides easily in snowpack tests or recent avalanches at any elevation, stick to lower-angle slopes.

 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2

    The most dangerous areas will be leeward sides of ridges and wind-exposed features 35 degrees and steeper. Avalanches in these areas could be big enough to bury or kill you. Use your probe to feel for stiffer, deeper drifts to indicate wind-loaded slopes. If you see recent avalanches or cracks shooting through the snow, stay on low-angle, wind-sheltered slopes.

    (1/17/2023)

    An example of natural wind slab avalanches near the base of a cliff. 

    Photo: Katie Warren

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    You may still be able to trigger avalanches on wind-sheltered slopes over 35 degrees. Look for stiffer snow over softer snow as an indicator that you can trigger storm slab avalanches. Use smaller, low-consequence test slopes to check how easily the snow slides. You can make many quick, informal tests as you move through the terrain.  Look at the interface that was buried at the beginning of this storm, about 1.5 feet below the surface. If you find sudden or propagating test results on the older, weak snow, stick to lower-angled slopes. If the sun warms the surface snow, you may see small loose wet avalanches on steep southerly aspects. 

    (1/9/2023)

    An example of a shallow storm slab beneath a rock outcrop.

    Photo: Willie Webster

Avalanche Discussion

On  Tuesday, observers near Vasiliki Ridge reported snowfall near 1"/hour with accumulations of at least 5" during the day. They were able to trigger small avalanches on unsupported test slopes near treeline. On Sunday, I went to Rainy Pass and found about 1 foot of snow that accumulated since Feb 3rd. The new snow was mostly well-bonded, tho in a few places we were able to find clean shears at the new/old interface.

There are a few weak layers that we've been tracking in the upper snowpack. The Jan 5th surface hoar (about 2-2.5ft below the surface) has been the most widespread and problematic in snowpack tests. At a profile on Sunday above Rainy Lake, test results indicated that the layer was not a problem for avalanches at that location. Elsewhere, especially in the eastern mountains, this layer could still be an issue if it gets stressed with the weight of enough new snow.

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