Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Clear “bulls-eye” data points to unstable snow, very dangerous avalanche conditions, and a natural avalanches cycle Friday. Stay away from anywhere an avalanche can start, run, or top.

Avalanche problems

  • Storm Slabs

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

    Even without the threat of the persistent weak layer lurking in the snowpack, this winter storm should produce significant avalanche activity. Heavy snowfall, mild temperatures, and strong winds all point towards natural avalanches within the new snow. These slides could serve as the trigger for the much deeper avalanches. Even if you don’t suspect a persistent slab issue exists, avoid all steep open slopes as this storm plays out.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–3

    Natural and/or human triggered avalanches occurred every day for the past 9 daysin the West South zone. Yet another remotely triggered slide took place outside of the skier area boundary at Crystal Mt on Thursday (5200’, ESE). We received reports of numerous avalanches near Crystal Mt, Mt St Helens, and White Pass over the past week. Some of these slides failed naturally, triggered remotely, stepped down into older layers, and caused other avalanches. Slides were documented in all elevation bands and on nearly every aspect. This persistent weak layer shows no signs of quieting down and may be just really waking-up. On Friday, significant new snow only makes this potentially dangerous snowpack structure scarier. This storm may tip the scales and produce a widespread avalanche cycle in some locations. Stay away from all avalanche terrain including where slide may run and stop.

    (2/5/2021) This avalanche was remotely triggered in backcountry terrain just outside of the Crystal ski area. Similar to other recent slides, it failed on facets just above the 1/13 crust. 60cm deep, 150' wide. 5200' ESE aspect. Photo: Crystal Mt Ski Patrol

Avalanche Discussion

Recent avalanche activity, persistent weak layers, heavy precipitation, relatively mild temperatures, and strong winds check nearly all of the potential “red-flag” boxes for unstable snow. While the bulk of the storm arrives before dawn, significant precipitation should carry over into the day and with it the threat for natural avalanches. A well-documented weak snowpack structure exists across the entire West-South zone. The primary layer of concern remains a layer of sugary facets just above the prominent and thick 1/13 crust. As of Thursday afternoon, this layer sat 2-3’ deep in the snowpack. It will only be deeper Friday morning. The vast majority of avalanches and unstable snow observations came from the Crystal area with slightly lesser numbers from Mt St Helens and White Pass. So far, no avalanches have been reported on this layer near Paradise. Regardless, a similar snowpack structure exists in all locations, and we could see avalanche cycles peak at different times in different parts of the zone. 

A second layer of concern exists in the upper snowpack. A thin crust (2/1) with weak facets potentially above and/or below has been observed in a few locations. So far, this layer did not hold a significant slab above it. As this storm piles up snow, that should change. 

You can use snow profiles and snowpack tests to monitor these persistent weak layers, but don’t employ them as decision-making tools. The clear “bulls-eye” data should speak much louder than any one hole in the snow. If you dig, help us track the weak layers by submitting an observation.

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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