Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

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

Nearly a week’s worth of daily natural and triggered avalanches highlights the ongoing dangerous conditions at Snoqualmie Pass. Exercise patients and give the snowpack time to adjust. Steer around open slopes greater than 35 degrees particularly at mid and upper elevations.

Avalanche problems

  • Storm Slabs

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

    Nearly a week of stormy weather just ended at the Pass. Fluctuating snow levels, strong winds, and heavy snowfall rates formed several potentially dangerous weak layers within the new snow. Numerous natural and triggered avalanches occurred as recently as Wednesday 2/17. Give the snowpack time to adjust and gain strength. While you can trigger a storm slab on any open slope greater than 35 degrees, pay particular attention to rocky slopes, convex rollovers, and areas where the wind drifted the snow deeper. Windy conditions during this storm likely formed deeper slabs on exposed terrain at mid and upper elevations. Avalanches on these slopes could be several feet thick. Due to the immense amount of recent snow, simple small slope tests and handpits might not provide you with reliable information concerning the presence of storm slabs. In these cases, patience might prove your best tool.

    (2/17/2021) This natural storm slab avalanche occurred on Kendall Peak Wednesday 2/17. SW, 5400'. SS-N-D1.5/R2-N Photo: Jonathon Spitzer

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3

    Our last recorded avalanche on the mid-January layer occurred a week ago. It can be easy to think the lack of recent avalanches means this layer is healing. However, the Pass just experienced a week-long storm cycle, and observations of any kind were incredibly difficult. Don’t let this lack of activity give you a sense of security. The uncertainty and consequences of this layer should shape where and how you travel. While triggering a slide on a deep persistent weak layer may prove difficult, any resulting avalanche would grow very large and destructive. Consider staying out of the startzones of large avalanche paths and limiting your exposure on the slopes below. Several avalanches on the mid-January layer triggered on slopes close to 30 degrees.

    (2/10/2021) This recent natural deep slab avalanche was observed from the Denny Trees area on Wednesday. It may have been triggered by a piece of cornice from above. Low Mountain, NE, 5000' HS-N-D2.5/R2-O, Photo: Jonathon Spitzer

Avalanche Discussion

Our next storm systems will arrive during the day Thursday. Daytime snow totals should do little to increase the avalanche hazard. However, as easterly winds ramp up later in the day, you may see new thin wind slabs forming in some locations. 

The recent storm cycle dropped 4-5’ of snow at the Pass since 2/11. Consequently, we received reports of natural and human-triggered avalanches every day since the 12th. Most recently natural avalanches on Low Mt (NE, 5200’, D2.5) and Kendall Peak (SW, 5400’, D1.5) were observed on Wednesday by professionals at the Pass. Avalanches during this long cycle generally failed on changes within the storm snow, however, several broke at the 2/11 interface where weak faceted grains were observed. This layer likely currently sits more than 3’ below the snow surface. If you dig deeper, you will still find the 2/1 and mid-January facets/crusts. Tracking and testing these deep persistent layers has become increasingly difficult as they get buried deeper. We believe these layers to rest about 7’ or more below the snow surface. 

With the recent storm, deep snow immersion and dangerous tree wells continue to pose a significant hazard. Please follow the link for more information. 

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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