Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

When you notice the warm temperatures and the sunshine, expect the snowpack to feel it too. If you see new rollerballs or fresh fan-shaped debris, steer around similar slopes. In more shaded locations, be leery of steep rocky and convex features where you suspect the wind may have piled the snow into thicker deposits.

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    “It’s warm out here,” was the common refrain on Wednesday, and we expect similar conditions Thursday. When warm temperatures, sunshine, and recent snow combine, expect natural loose avalanches from steep rocky slopes. It may take a few hours for the warm weather to overcome the strong morning inversion, but once it does, you could see the snow shedding from trees and rocks. This will serve as your first clue that the snow is feeling the heat. Anticipate new rollerballs and small natural avalanches on steep rocky slopes. Don’t let one of these small slides carry you into a creek, over a cliff, or through trees. If you see fresh fan-shaped debris, steer around similar slopes.

    (11/27/2020) Pinwheels at Mt. Rainier after rising freezing levels and the sun came out a few days after a storm. [S aspect 5400']

  • Wind Slabs

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

    Strong northwesterly winds formed slabs on lee slopes during Monday and Tuesday’s storm. These potential avalanches are now a few days old and becoming much harder to trigger. If you notice wind textured snow surfaces or find deeper wind deposits of snow, think about terrain features where you are more likely to trigger a wind slab. Be leery of rocky slopes, convex rollovers, and areas directly below cornices. Expect wind slabs to be larger as you ascend in elevation.

    (12/23/2020) Wind textured snow surfaces and drifts like these serves as great clues that the wind affected the snow pack and may have formed wind slabs on nearby slopes.

Avalanche Discussion

The recent storm left 4-8” (10-20cm) of snow over a very stout rain crust in most locations of the West-South zone. This new icy crust should limit any avalanche activity to the recent snow. You may still notice avalanche crowns and debris piles from a large natural avalanche cycle. These wet slabs occurred between Saturday night and Monday morning in many areas of the West South. Several were quite wide and even connected across terrain features. Rainy weather during this time period thoroughly tested the weak layers in the mid and upper snowpack. As a result, we expect recent weak layers (12/09 crust and 12/13 facets/surface hoar) to not currently be a concern. 

Expect temperature inversions Thursday morning in the valleys and at White Pass. As the day wears on, warmer air should move into the region pushing out these lingering cold pockets.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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