Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
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Out of date — this forecast expired 6 years ago.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

Dangerous conditions could develop by afternoon as winds increase. You may be able to trigger avalanches on freshly drifted slopes at upper elevation. Small loose avalanches are possible near and below treeline. 

Avalanche problems

  • Wind Slabs

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

    You could trigger wind slab avalanches on leeward sides of ridges and on cross-loaded terrain features at upper elevations. Avalanches may become easier to trigger as slabs build throughout the day. They will be bigger at higher elevations. Pay attention to signs of wind transported snow and recent drifting as the day goes on and as you climb onto higher slopes. Blowing snow, stiff, firm snow surfaces, and cracks shooting through the snow are all signs that you could trigger a slide. You can avoid these avalanches by sticking to sheltered terrain, traveling on slopes under 35 degrees, or choosing slopes where the wind isn't drifting fresh slabs of snow. 

    (2/11/2021) An example of cracks shooting through the snow in wind-exposed terrain on Thursday near Stevens Pass. This is a warning sign that you could trigger a wind slab avalanche. Photo: Josh Hirshberg

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    You can trigger loose avalanches on slopes 40 degrees and steeper where you find light, soft snow on the surface. Dry Loose avalanches can be dangerous if they catch you unaware. Pay attention to any moving snow around you and avoid steep slopes near terrain traps where an avalanche could push you off of a cliff, into trees, or bury you in a gully.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3

    Persistent slab avalanches may exist in outlying parts of the zone west of Washington Pass and in the eastern mountains. Audible whumphing collapses, cracks shooting through the snow, and widely propagating avalanches are all warning signs. You could trigger these slides on convex rolls and unsupported features. While the chances of triggering one of these avalanches have decreased, the consequences remain the same. If in doubt, opt for lower angle terrain and consider sticking to slopes less than 35 degrees.

    The last suspected persistent slab avalanche occurred near Rainy Pass on the 8th (see discussion). It may have run on facets over a crust (mid-January crust) about 2-3ft below the snow surface. While this weak layer hasn't been an issue just east of the pass for a while, it appears to have been more problematic at the far western and eastern edges of the zone. A layer of buried surface hoar and facets may still be found in the top 3 ft of the snowpack near Washington Pass. These layers caused both human triggered, and natural avalanches around February 2nd. 

    (2/9/2021) A very large avalanche at 6,400ft, ENE near Rainy Pass. This avalanche may have run on 8th on a deeply buried persistent weak layer. You can see many snowmobile tracks in the area. Photo: Jeff Ward

Avalanche Discussion

Light snow will continue for the Washington Pass area. Temperatures and wind will both increase, though only relative to the calm and cold conditions we've seen in the past few days

On Saturday, observers noted many loose snow avalanches in steep gullies at the Goat Wall. On Friday, observers found isolated wind slabs with shooting cracks in alpine locations near Silver Star. On February 9th, a very large avalanche was reported at 6,400ft, ENE near Rainy Pass (see photo below). It is suspected to have run on the mid-January crust-facet layer. An observer on Whistler Mountain reported sudden and propagating test results on a west aspect at 6,000ft as well as on a NW aspect at 6,600ft on this same layer. These facets over a crust can be found down about 2.5ft at 6,600ft in that area. This weak layer appears to be more shallowly buried and more problematic west of Washington Pass, as well as in the far eastern mountains of the Twisp River and Chewuch drainages. 

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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