Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

The best indicator of avalanche potential is recent avalanches, and we have had a lot of those in the West South recently. Continue to be patient and dial back your terrain choices as we navigate uncertainty around weak layers deep in the snowpack. Avoid areas of wind-affected snow where triggering an avalanche is more likely.

Avalanche problems

  • Persistent Slabs

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

    The Mid-January crust/facet combo which has been the cause of multiple avalanches over the past week and a half continues to exist throughout the zone. On Sunday, Crystal Patrollers were able to see a large to very large avalanche that had occurred on Crystal Peak at some point between Thursday and Saturday. These destructive avalanches have almost become the norm lately, and this layer shows no signs of quieting down in our zone.

    You can dig down to determine the existence of the Mid-January weak layer, but a single hole in the ground shouldn’t be a tool for ruling it out in your area. Continue to approach terrain over 30 degrees with caution. These slides can propagate widely and be triggered from far distances away. We have uncertainty about what it would take to trigger one of these avalanches right now, but if you trigger a large enough storm instability, the avalanche could step down to these layers. If you are caught in one of these avalanches at this point, it may be unsurvivable. 

    (2/6/2021) This slab was intentionally triggered by a small cornice drop on Saturday (2/6) in the Crystal backcountry. It propagated widely and is believed to have run on the Mid-January crust/facet combo. [E aspect, 6300'. Photo: Jeremy Allyn]

  • Wind Slabs

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

    We have been dealing with stormy conditions in the West South for almost a week straight, with this past weekend producing some of the biggest water numbers and wind speeds. In areas closer to the crest, strong winds have easily transported the storm snow into slabs. Although winds may not have been quite as strong as near the crest, the volcanoes surely formed plenty of Wind Slabs of their own. Look for Wind Slabs to have developed on leeward slopes near ridgelines or near rocky terrain such as cliffs and gullies. Convex rollovers or slopes over 35 degrees should be more prone to triggering avalanches, whether they are wind-loaded or not.

    With so much wind and fluctuating freezing levels, there should be plenty of density changes and interstorm layers in the upper snowpack for you to investigate in your pits. As you travel, you can use uptrack tests or test slopes to test how the recent snow is reacting to your weight. Look for visual clues such as textured snow surfaces, freshly built cornices, or smooth pillow-like piles of snow to help you identify where the wind has affected the snow. You could find that the snow feels firm and hollow, indicating a harder Wind Slab. You should avoid any slope greater than 35 degrees that you suspect is wind-loaded.

    (2/6/2021) Multiple slabs were observed on an E aspect at 6300' in the Crystal backcountry on Saturday (2/6). Deeper slides are suspected to have run on the Mid-January crust/facet combo while shallower Wind Slabs were also observed. [Photo: Jeremy Allyn]

Avalanche Discussion

The West South has consistently produced large to very large avalanches for over a week and a half. The only major location in the zone where we do not have a confirmed avalanche on the Mid-January (1/13) crust/facet combo is in the Paradise area. However, we have consistently confirmed the existence of a weak snowpack structure at Paradise. In fact, Paradise has a second layer of concern, the 2/1 crust, which was found to have weak snow above and below it. This second layer may or may not exist in other parts of the zone. It could present as just a density change, or could be associated with a small crust. The depth of these layers will vary across the zone, but you will know the Mid-January crust when you get there. Look around 30cm above this crust to find the 2/1 interface.

With the amount of snow we just received, the hazard rating would be Considerable on Monday even without the existence of these potential deeper instabilities, and we would likely be hearing about plenty of avalanches by Monday night. The confirmed weak snowpack structure should have you choosing even more conservative terrain than you normally would as a storm winds down. If you do head out, use caution and let us know what you see by submitting a public 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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