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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Dangerous avalanche conditions will exist at Snoqualmie Pass on Saturday. New snow, wind, and a weak snowpack are a recipe for reactive and potentially surprising avalanches. You should avoid slopes over 35 degrees where triggering a slide is more likely.

Avalanche problems

  • Storm Slabs

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

    You are likely to trigger an avalanche on slopes over 35 degrees, particularly ones that are convex, unsupported, or wind-loaded. Well over a foot of recent snow exists over the 12/30 crust at middle and upper elevations, meaning the depth is there for large avalanches to occur. Some of these could break widely or in surprising ways by failing on buried weak snow grains. Take note of whumpfing collapses, shooting cracks, or recent avalanches as you travel. These red flag signs of instability indicate that the snowpack is unhappy, and you should avoid slopes over 35 degrees. 

    Avalanches could step down to older layers in isolated locations, resulting in even larger slides.

    (1/4/2024)

    The crown of a large natural avalanche that occurred at Alpental on Thursday. It most likely ran on the 12/30 crust. [SS-N-D2-R2-O]

    Photo: Alpental Pro Patrol

Avalanche Discussion

All the ingredients appear to be in place for slab avalanches to occur on Saturday - incoming new snow, wind, a weak upper snowpack structure, and a good crust for snow to run far and fast on. 

This week, a parade of small storms has delivered roughly 15 inches of new snow to the Pass and steadily increased avalanche potential. Friday night and Saturday, we could get up to another foot. All of this snow will be sitting atop the 12/30 crust. Weak snow (buried surface hoar) has been identified by NWAC and avalanche professionals above this crust at multiple locations in the zone. Smaller avalanches have reportedly run on this layer in recent days. The 12/30 is where you should target your snowpack observations on Saturday. It will be the first significant crust you encounter when digging down with your hand or shovel. Depending on your elevation, you may find the thinner 1/4 crust before reaching the 12/30. On Friday, NWAC and avalanche professionals produced easy failures at this layer with snowpack tests.

There are other potential weak points in the upper snowpack. We’ve been discussing them in more detail recently, including the Solstice Crust and 12/25. You can take a look back at this week’s forecasts to gain a better understanding of them. For Saturday, you should know that they are down there. Some have propagated in large columns tests this week, and any could reach a tipping point this weekend. That could be by human triggers or, more likely, another avalanche stepping down.

We know that this is an exciting time for backcountry enthusiasts. We’ve all been hungry for a cold and snowy weekend. Try to show some restraint. Saturday has the potential to be quite dangerous. It is not the time to jump into big terrain that has been off-limits all season.

This week's snow has helped improve travel conditions, and this next wave should continue that trend. That said, objects that were easy to spot, such as open creeks or boulders, are now barely hidden out of view. Continue to tread lightly out there, particularly at lower elevations.

This is the time to let us know how your day played out. Whether you saw avalanches or not, are hiking, snowmo'ing, skiing, or in a class.  If you’re heading out, please submit an observation.

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