Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Look for new and old areas of wind-stiffened snow to steer around on Saturday as conditions start to change at Snoqualmie Pass. Recent snow may not have stuck to steeper slopes very well and could slide downhill easily given a human trigger. If you find strong snow over weak snow or experience signs of instability such as whumpfing collapses or shooting cracks as you travel, consider dialing back your terrain choices.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    The pass is set to pick up another couple inches of snow with fairly light winds on Saturday. This seems like a repeating pattern over the past few days as we have slowly built the snow depth over the 1/13 AR crust. Areas of wind drifted snow have been observed at the pass recently and should continue to be the most consequential potential avalanches on Saturday. There may be freshly developed Wind Slabs if winds are strong enough to move low-density snow around. Older Wind Slabs may still be reactive but buried by a few inches of new snow. Regardless of their formation date, these pockets of reactive snow may be more likely near rocky features or on leeward slopes near ridgelines. Feel for subtle changes in the snow as you travel, look for textured snow surfaces, and use test slopes to check the reactivity of all the snow sitting atop the 1/13 crust. Avoid terrain features greater than 35 degrees if you suspect that they are wind-loaded.

    (12/22/2020) Example: a small wind slab in a confined terrain feature. You may see similar slides on Saturday.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    In areas where the wind has not been able to move the snow into a more cohesive slab, you may encounter some loose avalanches. The recent storm snow sitting atop the 1/13 crust is poorly bonded in many locations and could “sluff” off easily given a human trigger. These slides could run far and fast on the firm crust, fanning out as they descend. Don’t let one surprise you on steep slopes or near terrain traps where a simple fall or small avalanche could have serious consequences.

    (3/8/2020) Example of a Dry Loose triggered by a skier. Don't let one of these catch you in consequential terrain.

Avalanche Discussion

This week we have slowly been transitioning toward higher avalanche danger at Snoqualmie Pass as we increase the snow depth above the 1/13 AR crust. Weak snow grains sitting atop this crust continued to be positively identified by professionals in the zone, and are our biggest concern moving forward. We have not had a lot of activity on these weak layers as of yet, but as temperatures warm and we continue to add snow load, that could change. We continue to talk about Wind Slabs since we believe that wind loaded areas are where the most slab potential currently exists to possibly fail on these persistent grain types. Travelers recently have reported whumpfing collapses and shooting cracks in the snow, most occurring in wind-affected areas. As conditions change this weekend, these red flag signs of instability should give you pause and steer you to low consequence terrain. As we navigate this complex setup with a bit of uncertainty, we’d appreciate hearing what you are seeing out there if you can take a few minutes to submit a public observation. 

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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