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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

New wind-drifted and older deep snow layers continue to keep us on our toes and maintain potentially unstable conditions. Steer around steep open areas especially where you see the wind blowing snow onto a slope. With so much recent snow, any avalanche may grow sizable and dangerous.

Avalanche problems

  • Wind Slabs

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

    Turn your attention to the wind drifted new snow. Watch for blowing snow and fresh cornices to help you identify which aspects and features may hold newly formed wind slabs. As the day continues strong winds could help some of these slabs grow deeper and more dangerous. Even as you travel through more sheltered terrain, keep an eye on the ridgelines above you. If you notice the snow blown out of the trees or see hazy plumes off peaks, the wind is transporting the new snow.  If you suspect the wind loaded snow onto a slope, give it a wide berth and seek out more sheltered or lower angled terrain. With the strong and sustained nature of this wind event, you may encounter wind slabs on exposed slopes at any elevation particularly in the more wind-prone I90 corridor.

    (2/18/2021) These natural wind slab avalanches likely failed Tuesday or Wednesday (2/16-17) on Kendall Peak near Snoqualmie Pass. SW 5400. SS-N-D1.5/R2-N.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3

    Our lack of confidence in the snowpack continues to weigh heavily on our forecasts. Recent snow profiles and snowpack tests continue to indicate that the mid-January crust/facet layer remains intact and may produce avalanches. While we haven’t heard of slides on this layer over the past week, recent storms significantly limited observations. Now, during this relative break in the weather, the urge to step-out into larger terrain is palpable. However, let the uncertainty and potential consequences of this deep persistent weak layer shape your terrain decisions. Consider staying out of large open startzones and limiting the time you spend on the slopes below them. You may trigger a deep avalanche from a thin spot in the snowpack or if a smaller slide steps down into these older layers. Any resulting avalanche would certainly grow very large and destructive.

    (2/18/2021) This snow profile shows the upper 7+ ft of the snowpack. You can see all three prominent persistent layers mentioned in the forecast.

Avalanche Discussion

The Pass received 6-9” of snow Thursday into Friday. Reports of several small natural and human-triggered avalanches occurred on steep convex rollovers earlier in the day. Observations indicate that many of these storm snow weaknesses were short-lived. As snow showers and windy conditions continue at the Pass, it should only serve to maintain the avalanche hazard with recent snow layers gaining strength and new weak layers forming. 

Conditions around the Pass are deep! The snow stake at the top of Alpental (~5400’) shows more than 200” of snow on the ground. Hiding in all this snow lie several persistent weak layers. The most notable continues to remain the mid-January crust/facet layer. You may find these potential weak grains 6ft or more below the snow surface. Sugar facets sit just above the very thick and prominent crust formed during mid-January. We believe this layer to be most concerning above 4000’ in the Snoqualmie area. Our last known avalanche on this layer occurred Wednesday, Feb 10 on Low Mt (NE, 5000’). 

With all the recent snow, tree well and deep snow hazards exist. Please follow this 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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