Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

A potentially dangerous snowpack structure may combine with recent windy weather to create challenging avalanche conditions. Several recent natural and human triggered slides highlight the current hazard. Keep your terrain choices dialed back, and seek out thickly treed or lower angled slopes.

Avalanche problems

  • Wind Slabs

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

    Several wind events over the past few days formed slabs on a variety of aspects and features including on some unusual slopes.  With this criss-cross nature of overlapping wind slabs, you’ll need to keep a careful watch for signs of wind affected snow. In some locations, a few inches of soft snow may hide obvious clues from view. Look and feel for wind slabs as you travel. Ask yourself, does the snow feel different underneath me? Do I see small drifts behind trees? Are some slopes scoured? These questions can help you identify wind loaded locations. If you suspect the wind drifted snow onto a slope, steer around and seek out lower angled or thickly treed terrain. 

    To make matters more complicated, these wind slabs may overlay weak facets on some slopes allowing them to trigger easily or produce larger avalanches. Even though wind slabs commonly occur in this zone, resist the urge to treat these as your “run of the mill” wind slabs. Give yourself a little extra buffer with these tricky and potentially dangerous overlapping problems.

    (2/1/2021) This small wind slab avalanche stepped down to the 1/23 facets above the thick prominent crust. White Pass: Gunsight Bowl: N aspect, 6300', 18" crown. HS-ASc-D1.5-R2-O

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    A buried layer of weak facets exists in the snowpack throughout the West South zone. These sugary grains produce numerous avalanches, shooting cracks, and collapses in the Crystal, White Pass, and Mt St Helens areas. Travelers triggered slides remotely, saw slabs step-down into older snow, and witnessed avalanches triggering other avalanches. Like an unwanted house guest, this problem just doesn’t seem to want to go away. At this point, 18-30” of snow overlays this persistent weak layer on many slopes. As a result, you could trigger a deep and potentially deadly avalanche. Snow profiles and snowpack tests can help you track this layer, however, they should not serve as your decision-making tool. Don’t bet your life on a hole in the snow. Keep your terrain selection dialed back and stay off of open slopes greater than 30 degrees.

    (1/29/2021) Multiple slabs were remotely triggered from a far distance by a snowmobiler on Mt. Saint Helens on Friday (1/29). There were multiple other slides remotely triggered and observed on the same day. [Photo: Kurt Heine]

Avalanche Discussion

The recent active weather should start to wind down Tuesday night. Normally, we relate the end of the storm with a decline in avalanche danger. Due to the persistent nature of our avalanche problems, that likely will not occur. Stay on your toes. You may find a layer of weak facets just above the prominent 1/13 crust. You could also see a thin crust or buried surface hoar along with these sugary grains. While this snowpack structure seems to exist on all slopes, the bulk of the avalanches and shooting cracks occurred on E-S-W aspects near or just above treeline at Crystal Mt, White Pass, and Mt St Helens. So far, observations at Paradise and in the Tatoosh found this structure, but no avalanches were reported. Thank you to the community for all your recent observations! Please keep them coming as we track this persistent weak layer. 

At lower elevations (<5000-5500’) rain on Monday wetted the upper snowpack. Now, cooler temperatures and additional snow should help minimize the avalanche danger. Instead, you could see challenging travel conditions that include breakable crust or punchy wet snow.

Regions covered