Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

You should find more winter-like weather helping to maintain dangerous avalanche conditions on Wednesday at Snoqualmie Pass. You will have to actively manage new snow problems, but the lingering wet problems should be what shape your travel plans. If you head into the mountains, ease back into terrain by avoiding slopes over 35 degrees and areas with overhead hazard.

Avalanche problems

  • Wind Slabs

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

    Winds on Tuesday evening will easily be strong enough to move around newly fallen snow into Wind Slabs. These slabs should be thicker, and possibly more reactive as you ascend in elevation. You are most likely to find them in exposed areas near the leeward side of ridgelines or on convex slopes. Freshly built cornices, textured surfaces, or fresh drifts behind natural objects can help you identify potentially unstable slopes to avoid. 

    In more protected areas, we expect new snow to bond fairly well to a generally warm and wet surface. That doesn’t mean that stability is a guarantee, however. Take some time to use uptrack tests, hand pits, or small test slopes to see how the new snow has bonded or if it has come in upside down (heavy snow over weaker snow). When in doubt, avoid slopes over 35 degrees whether they are wind-loaded or not. 

    (12/18/2022)

    Example: A shallow human-triggered slab avalanche that caught and carried two skiers on 12/18.  You may have to manage similar slabs on Wednesday. [NW 5100']

    Photo: Public Observation

  • Glide Cracks

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

    Wet avalanches will continue to be a concern on Wednesday, despite the cooling temperatures and return to snow. Liquid water can linger in the snowpack and produce avalanches for days after it has stopped raining. Keep an eye out for large crevasse-like cracks, hanging blocks of snow, or sagging cornices that could release unexpectedly and produce a large avalanche. These avalanches are unpredictable, so your best mitigation tool is to recognize the terrain where they are more likely and give it a wide berth.

    (12/26/2022)

    A glide avalanche in Shot 6 at Alpental, plus a separate Glide crack where the snow has not yet released. 

    Photo: Alpental Pro Patrol

Avalanche Discussion

The pass picked up another 1” of water on Tuesday, bringing the total since 12/23 somewhere in the 4.5-6.5” range. The silver lining is that some of this fell as snow (~3-4”) at upper elevations as temperatures slowly cooled. This general cooling trend should continue overnight on Tuesday into Wednesday as another shot of heavy precipitation and strong winds impact the zone. It will likely still be quite stormy in the morning hours on Wednesday before the weather starts to ease. Most trailheads near the pass proper should see snow falling from the sky instead of rain by day’s end.

As this transition away from warm and wet continues, the snowpack should start to refreeze and stabilize from the top down. How long this process takes is unknown at this point, but it could take some time. This is a slow cooldown, we’re not exactly being thrown back into the freezer.  On Tuesday, another Glide avalanche was reported by Alpental Pro Patrol, making it two in two days. This sort of activity could continue until we have had several days of cool weather.

At lower to mid elevations, a stout freezing rain crust caps the snowpack in many areas. This could act as a good sliding surface or may have just enough roughness to allow wet snow to bond. The crust and swollen or blown-out creeks at these elevations could make travel quite difficult as we roll back the clock to early-season conditions. As you ascend in elevation, the crust should dissipate and become more breakable. New snow will be falling on what is believed to be a beat-up and moist snowpack at these elevations. Unfortunately, much of the damage has already been done and you could still encounter early-season hazards or heavy punchy conditions even as new snow piles up. 

If you decide that Wednesday is your day to return to the mountains, please help our general understanding of the conditions by letting us know what you see. There is a lot of uncertainty around what happened during this cycle and how conditions are shaping up as we transition. What we do know is that whenever you do make it back out there, the mountains will look a lot different than when you last visited.

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