Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The snowpack will still need time to adjust to the recent load from Tuesday’s storm. Let nature do its thing by avoiding slopes over 35 degrees for another day. If you head into the mountains, be sure to bundle up. The Solstice is going to be a chilly one.

Avalanche problems

  • Storm Slabs

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

    Slabs will be less than 24 hours old when you step out of your car on Wednesday and will likely still need time to heal. You should use small test slopes, uptrack tests, or hand pits to determine how easily the snow is failing and if there is a poor bond to the underlying layers. Even if it is soft, snow that fails in blocks or produces a crown is in fact a slab and should grab your attention. 

    In more exposed areas, you may have to deal with thicker and stiffer Wind Slabs. Depending on your elevation, these may exist on different aspects, so look for freshly built cornices or smooth pillow-like piles of snow to help you identify wind-loaded slopes to avoid. Although these slabs are categorized differently, the way you should manage them is mostly the same. You should avoid slopes over 35 degrees where triggering a slab avalanche is more likely.

    (12/20/2022)

    This tiny slab was triggered remotely on an unsupported feature while a skier was breaking trail in the neighboring Snoqualmie Pass zone on 12/20. Notice the long shooting crack. 

    Photo: Public Observation

Avalanche Discussion

Tuesday’s storm packed quite the punch and delivered over a foot of snow to most areas throughout the West South zone. Accompanying these impressive snow totals were even more impressive winds.  NWAC weather stations recorded gusts into the 70s and 80s both on the volcanoes and near the crest. 

Observations were limited, likely due to the ferocity of the storm, but Crystal Mountain Pro Patrol reported sensitive Storm Slabs, Wind Slabs, and fresh cornices during their mitigation work on Tuesday morning. As temperatures warmed and precipitation increased, we received some word that the snow was getting a bit upside-down (heavy snow over weak snow). This may have helped drive more widespread Storm Slab issues. In the neighboring Snoqualmie Pass zone, we have a bit more feedback from the day. It was very active with small avalanches on almost every convexity or unsupported slope you could find in the morning. Some of these were triggered remotely with long shooting cracks. 

A general cooling trend and an end to the stormy weather await on Wednesday, and it should be downright frigid out there. If you’re in the mountains, be sure to dress appropriately and keep your partners in sight with all of this new snow. While no avalanches have been confirmed on our buried weak layers in the snowpack, we are still keeping them on our radar for the duration of the week. 

Our southern volcanoes may have shown up to the storm party a little later (and a little warmer) than the northern half of our zone. While this forecast should hold well, you may want to also reference the Mt. Hood forecast for additional information before heading out to these areas. Slabs will be newer and the winds were likely stronger.

Regions covered