Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

If you travel in the mountains on Saturday, be prepared for winter storm conditions and the threat of avalanches on slopes greater than 35 degrees. You can look for recent avalanches or cracking of the snowpack as indicators of avalanche potential. Make conservative decisions and keep in mind that early season conditions still exist. 

Avalanche problems

  • Storm Slabs

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

    The weather on Saturday should be a recipe for Storm Slabs to develop at all elevation bands. These slabs will be thicker and possibly more reactive as you ascend in elevation or on wind-loaded slopes. Multiple storm layers and density changes are expected above the Late November Crust, so you will need to dig down and investigate the snowpack before committing to terrain. Using test slopes to look for slab potential and reactivity can give you more direct feedback on how these layers may react to your weight. If you notice signs of unstable snow, see avalanches, or find heavy snow over light snow in your pits, avoid slopes over 35 degrees.

    (12/10/2021)

    Simple snowpack tests like this can help you to identify interstorm layers that may be of concern. This layer was identified about 10cm down where warming had caused an "upside-down" snowpack to start to develop on Friday, 12/10.

    Photo: Robin Pendery

Avalanche Discussion

Almost continuous snow since Wednesday 12/8 has increased the depth of our early season snowpack and expanded the terrain where avalanches can occur. Saturday should be the biggest punch this round of storms has to offer, and it will be a dangerous day to be in the mountains. Observations continue to be limited, but a recent human-triggered avalanche on Thursday evening, combined with reports from professionals are leading us to believe that some of the recent storm layers may be capable of producing surprising avalanches. 

A bump in temperatures on Saturday morning could result in a wintery mix or even rain below ~3500 feet. This bump should aid in Storm Slab development by creating heavy over light snow (an “upside-down” snowpack) at most elevations. Additionally, the possibility of some small Wet Loose avalanches due to rain falling on dry snow can’t be ruled out below 3500 feet. 

Keep in mind that despite the new snow, early season conditions still exist. Open creeks, rocks, stumps, and other natural hazards that may have been visible on Friday could be just buried under the surface on Saturday. Take it slow and ease into winter, we are just getting started.

"Uphill travel reminder: Check in with your local ski area this weekend regarding terrain access and parking updates. Closed ski areas often share a similar snowpack and avalanche hazard as the surrounding backcountry. You may also encounter other hazards like active avalanche mitigation, unmarked obstacles, snowmobiles, groomers, and other heavy equipment as ski areas prepare to open. Be prepared to make your own assessments and handle emergency situations.”

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