Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 6 years ago.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

Highlights

Even as the stormy weather eases Wednesday, you may still trigger avalanches in specific areas especially as you ascend in elevation. Steer around features such as convex rollovers, steep rocky slopes, and areas the wind drifted the snow.

Avalanche problems

  • Storm Slabs

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

    Several human triggered avalanches occur over the past several days in the Snoqualmie Pass zone. Changes in temperature, wind speed, and precipitation rate created several inter-storm layers that could continue to fail and cause avalanches. Even as you experience a relative break in the storm Wednesday, think about features where you will be more likely to trigger an avalanche. Steer around possible trigger points such as convex rollovers, steep rocky slopes, and areas where the wind drifted the snow deeper. Use small inconsequential slopes to test the snow and see how or if it fails under your weight. Up track tests, small slope cuts, and simple hand pits can provide you with information to confirm the storm slab problem. In more wind prone location, simple visual clues such as cornices and firm hollow snow may indicate that avalanches are possible. 

    One large area of uncertainty continues to linger over the Snoqualmie avalanche forecast; the possibility of a buried persistent weak layer that could be inching towards a breaking point. Facets and/or buried surface hoar could exist about 4”/10cm above the very prominent crust (12/09). If you see large shooting cracks or experience collapses, you may have found this buried weak layer, and it’s time to substantially dial back your terrain choice. You’re most likely to find these buried persistent grains on shaded and sheltered aspects at any elevation.

    (12/15/2020) Example: This natural storm slab occurred at Lanham Creek near Stevens Pass. It failed on a change in snow crystal type within the storm snow. NE aspect 5200' N-SS-D1-I

Avalanche Discussion

A series of winter storms continue to add to the snowpack. While no one of these systems has been very impressive, some locations now hold more than a foot of recent snow over a very prominent and stout crust (12/09). As we continue to add a few more inches, we have to wonder if we’re getting close to the tipping point and a larger avalanche cycle. With the modest new snowfall expected for Wednesday, we don’t look for this to be the big day. 

At lower elevations, minimal new snow and even some rain continue to keep the avalanche danger limited. Instead, expect demanding travel conditions with open creeks, shallowly buried objects, and thin coverage below the forest. 

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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