Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Slab avalanches will be easier to trigger on steep slopes over 35 degrees, particularly where wind drifting has occurred. However, the threat of triggering a very large avalanche should be what shapes your travel plans. Keep an eye on your buddy in the deep snow and frigid temperatures. 

Avalanche problems

  • Wind Slabs

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

    Wind slabs will be more likely in areas closer to the crest or a mountain gap where easterly winds will be stronger. Due to the atypical wind direction, slabs may form on different aspects than you’re used to. There also likely will be more mid-slope cross-loading. Visual clues such as fresh cornices, actively blowing snow, or textured surfaces can help you identify where new slabs are forming. Additionally, there could be older slabs hidden beneath the surface. You’ll need to feel for changes in the density of the snow as you travel to identify them. Small test slopes and uptrack tests can indicate how the snow is reacting to your weight as a traveler.

    (1/11/2024)

    Small, remotely triggered slab avalanche at White Pass.

    Photo: Dallas Glass

  • Persistent Slabs

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

    We’ve been talking about weak layers in the snowpack for a while. Some slopes reached their tipping point this week. Natural and explosive triggered slides have been breaking on the 12/30 and Solstice Crusts within the zone, producing very large avalanches that propagated widely and wrapped terrain features. This isn’t a problem you can tiptoe around. We’ve found a poor snowpack structure everywhere we have dug a hole in recent weeks. The question mark is not about size or distribution but the sensitivity to triggering. Now that you know what’s below your feet and that it can produce unsurvivable avalanches, your best mitigation tool will be to stay off open steep slopes to minimize the possibility of you triggering one. 

    (1/11/2024)

    Explosive triggered persistent slab avalanches at Crystal Mountain. These occurred on Thursday, 1/11. 

    Photo: Crystal Mountain Pro Patrol

Avalanche Discussion

Saturday will be a mixed bag of conditions across the West South zone. The southern volcanoes may get another shot of snow. Areas closer to the crest or mountain gaps will get more robust winds. Wherever you are, the temperatures will be downright frigid. Be prepared by bringing extra layers, hand warmers, face masks, and ensure those grip heaters work.

Overall, calmer conditions are expected than we have seen over the past week. During that time, over 4 feet of snow fell around the West South, and Paradise was the first NWAC weather station to reach 100 inches this season. 

As a result, there are interstorm density changes, graupel, and the potential for dry loose. These are your standard PNW storm issues that you’ll need to continue to manage on Saturday. Slab avalanches were easily triggered on Thursday at White Pass and near Crystal Mountain.

Unfortunately, you’ll also need to manage those deeper, persistent weak layers. Multiple persistent slabs have failed going back to last Saturday, 11/6. Natural slides occurred at Mount Rainier and near Crystal Mountain. On Wednesday and Thursday of this week, Crystal Mountain Pro Patrol triggered multiple very large (D3) persistent slabs during their morning mitigation work. We’re still gathering information about what may be needed to trigger one of these slides and where it’s more likely. We do know that they have started to fail, and if you trigger one, it likely will be unsurvivable.

Regions covered