Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Unusual times call for an unusual forecast, so that’s what you’re getting. Uncertainty around buried weak grains is preventing us from claiming that all is well and good in the snowpack. You may even still be able to find a lingering Wind Slab or trigger some loose snow if you venture to high elevation or extreme terrain. Be sure to evaluate the snowpack carefully before committing to a slope.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1.5–2.5

    Persistent slabs are a tricky avalanche problem to deal with. You could be out in the mountains all day and not see any signs of instability and then all of a sudden find the sweet spot where you trigger a large and potentially deadly avalanche. These avalanches can fail in surprising ways by spanning far distances, breaking above you, or wrapping around and connecting terrain features. Your best mitigation tool is to choose lower-angled terrain where you’re less likely to trigger one of these beasts.

    (12/9/2022)

    This skier-triggered avalanche occurred Friday 12/9 in the Alpental Valley and likely failed at the 12/8 interface. [N-NE, ~4000ft. SS-AS-D1-R1-U]

Avalanche Discussion

While not unprecedented, this has been an unusual start to the season which has led to some unusual early-season challenges. The generally cold temperatures, amount of snow, and to be frank, lack of rain, have given us pretty good early-season coverage, but perhaps a less-than-ideal snowpack structure. At Snoqualmie Pass, we do not yet have a confirmed avalanche on the 12/8 buried surface hoar layer but have confirmed weak snow does exist at this interface, at least in spotty locations. We also know there were 3 human-triggered avalanches on Friday 12/9 that had crown depths that are close to matching that of 12/8. While the likelihood of you triggering an avalanche on this layer is low, there is enough uncertainty that we cannot call conditions generally safe at this time. If you do trigger one, the slide will most certainly be large enough to bury or kill you. While the BTL is not out of the question for this avalanche problem, we do feel that there is even less of a chance of you running into an issue. 

You will likely find the 12/8 around 1-1.5 feet below the surface depending on where you are in the zone. There is still minimal information about its distribution, and known test results seem to highlight the layer easily but do not show much in the way of propagation. In some areas, this layer may seem just like your run-of-the-mill storm interface. In others, you could find that it breaks cleanly and smoothly on some sparkly snow grains (surface hoar). Regardless of the grain type and its fracture quality, it does appear that this storm interface is taking longer to heal than we would typically see in the Cascades, which should have you thinking. In other zones throughout the region, this layer has woken up and produced avalanches, so there may be a time when we reach the tipping point at Snoqualmie. On the flip side, there’s the possibility that time may never come. We’re not ready to make that call quite yet and are still traveling cautiously with the knowledge that this layer exists.

If you take advantage of the nicer weather to venture to the highest peaks or more extreme terrain, you may still be able to find some lingering storm instabilities in the way of Wind Slabs or loose avalanches. Maybe the sunshine will help some snow shed from trees and rocks, grabbing a bit of snow as they descend steeper slopes below. At lower elevations, you may still need to manage some early-season hazards such as creeks, holes, or small trees and bushes.

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