Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

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

As the stormy weather continues Thursday avalanches could become more widespread and larger, especially at upper elevations. You will likely find the most dangerous conditions on slopes where the wind drifts the snow into firmer and deeper slabs. Blowing snow and fresh cornices can help show you which steep slopes to avoid.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    The wind will be the primary architect of the avalanche danger during this storm. Moderate to strong winds and continued light snowfall should combine perfectly to form new wind slabs. This avalanche problem is often hard to assess. Instead look for clues like blowing snow, sharp cornices, and textures snow surfaces to indicate which slopes hold wind-loaded snow. Don’t try to test these features, any avalanche could be more than a foot thick and large enough to kill you. As the windy conditions persist throughout the day, you may find wind slabs in more areas. Look for them around ridgelines, the tops of gullies, and on rocky slopes.

    (12/17/2021)

    Sharp cornices hanging over the Middle Fork valley. Clues like this hint at winds slabs on the slopes below. 

    Photo: Dallas Glass

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Generally cooling temperatures, light snowfall rates, and a good bond to the old snow surface should help limit any storm slab development. However, as the snow continues to pile up at mid and lower elevations, it’s worth considering where you may trigger a small avalanche. Don’t be surprised if you trigger a shallow slab in very steep terrain or on convex slopes. Heavier snowfall rates may be the first clue that storm slabs are becoming more likely. If you see more than an inch of snow accumulating every hour for several hours straight, storm slabs could develop. As you travel, take time to stop and use your hand to dig in the snow. If you find stronger over weaker snow, or if blocks fail easily, it may be time to dial it back and stay off of open areas greater than 35 degrees.

    (12/22/2021)

    You can dig with your hand to look at the new storm snow and search for strong over weak slabs. 

    Photo: Andy Harrington

Avalanche Discussion

Despite the ongoing storm, there’s a lot going in our favor and keeping more widespread avalanche danger at bay. The snow warmed significantly on Tuesday and continued rain at mid and lower elevations Wednesday allowed the snow to bond well to the old surface. As temperatures continue to cool, this previously wet snow should freeze and form a new crust (12/22). This same cooling pattern should help the new snow fall mostly right-side-up, limiting slab development. However, at some point, you can’t ignore the growing storm totals, especially at upper elevations. On Tuesday more than a foot of snow fell at the top of Alpental while only 2-3 inches accumulated at Pass level. As a result, the avalanche danger could rise dramatically as you ascend through near treeline terrain. 

Wednesday, NWAC staff and Alpental patrol both reported similar conditions. While the upper snowpack still contains recent storm layers, the newly forming crust (12/22) should limit avalanches to the new snow. Freezing rain changed to rain and finally to snow at lower elevations Tuesday afternoon. This resulted in some tricky travel conditions including icy slopes and lots of tree bombs. As more snow falls, conditions should improve dramatically. Several loose wet avalanches were reported from Tuesday's warm and sunny weather. Don't be surprised if you see old piles of very firm debris coveredby the new snow. 

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