Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

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

It’s deep out there and another winter storm will impact the region Tuesday night. You can trigger weak layers within the storm snow on steep open slopes at all elevations. With all the recent snow, any avalanche can grow large and deadly. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    The last in a long parade of winter storms should hit Snoqualmie Pass Tuesday night into Wednesday morning forming new storm snow layers that you can trigger. At this point in the storm cycle, any avalanche that starts may entrain significant snow and become large and deadly. Dial it back and seek out lower angled or treed terrain to avoid the storm snow hazards. You can use small slopes to test the shallower new storm snow, however, with so many potential weak layers in the upper snowpack, these observations may not tell you everything you need to know. Use patience and give the snowpack time to adjust to all the recent snow. 

    Near and below the rain-snow line Wednesday, you may find wet and unstable surface snow. If you see new rollerballs or find fresh piles of debris, steer around similar terrain. While getting this deep heavy snow to start moving may prove difficult, once it does, it may gouge and produce large avalanches.

    (1/5/2021) Natural storm slabs on Mt Snoqualmie. SW, 5200' These likely occurred on Monday during the stormy weather. Other crowns were seen on various aspects between 5000-6000'

Avalanche Discussion

This storm should peak overnight and could produce a natural avalanche cycle during periods of heavy snowfall and strong winds. You will likely see the highest avalanche danger in the morning. As the day continues, you may find the new snow layers becoming stronger. This storm arrives as part of a week-long storm cycle that, as of Tuesday afternoon, brought 10.8” of precipitation and more than 5-6’ of snow to the Pass. Numerous potential weak layers exist in the upper snowpack. On Tuesday, NWAC staff observed several very large crowns on Chair Peak (E 5600, E 5400). We don’t know when these slides occurred but they highlight the potential for avalanches to fail on deeper layers of the snowpack and produce isolated very large and destructive slides. This also demonstrates the high level of uncertainty in the snowpack at mid and upper elevations. If you travel to higher terrain, be leery of the very large avalanche paths that originate there.

Two layers serve as notable snowpack markers you can use to assess the recent storms. On New Years Day, a crust was formed and buried at nearly all elevations. This may appear like an ice lens above 4000’ and, as of Tuesday,  was 70-85cm below the snow surface. The prominent 12/21 crust still serves as a reference and may be found  180-200cm below the surface. 

In addition to dangerous avalanche conditions, non-avalanche hazards exist including tree well and deep snow immersion. Find out more information about deep snow safety HERE.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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