Lawinenlagebericht

West Slopes South

Northwest Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Veraltet — dieser Lagebericht ist 5 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Focus on the consequences rather than the danger rating when considering where and how you want to travel Sunday. Enormous and destructive avalanches occurred this week. Limit your time in and around very large avalanche paths including areas where they may run or stop.

Lawinenprobleme

  • Deep Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    3

    Don’t let the moderate avalanche danger rating deceive you. The dire consequences of experiencing a deep slab remain the same. Cooler weather this weekend, a strengthening upper snowpack, and the lack of avalanches over the past few days gives us a bit of hope. However, the mid-January facets/crust layer stayed largely unchanged. Consider limiting or even fully avoiding very large avalanche paths. This should include areas below treeline where these giant slides could run and stop. Avalanches last weekend broke trees and ran near the bottom of their historical runouts. 

    Observing, assessing, and forecasting deep slabs can prove very difficult. Most of our normal observations fail to provide meaningful information regarding the layers 6-10’ beneath you. Instead, focus on what you know. A significant weak layer has been well documented in all areas of the West South zone and very large and destructive slides occurred over the past several weeks. Keep your conversation and decisions centered on these facts rather than potentially misleading surface observations.

    (2/27/2021) This slide within Crystal Mountain Ski Resort was triggered by a single explosive during control work on Saturday (2/27) and is confirmed to have run on the Mid-January crust/facet combo. [5700' E aspect; Photo: Crystal Mountain Pro Patrol]

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1

    You may encounter shallow wind slabs near ridgelines and on exposed features Sunday. These potential slides should remain small, but could still harm you if they push you over a cliff or into rocks. They may also serve as a trigger for the much scarier deep slabs in bigger terrain. Watch for blowing snow and small drifts to help you identify potentially wind-loaded areas. Pay particular attention to slopes below cornices, near rocks, or in confined features where these thin slabs may trigger more easily.

    (2/1/2021) Example: This wind slab occurred in a relatively confined chute near White Pass earlier this winter.

Avalanche Discussion

Reports on Saturday noted 2-4” of new snow around the West South zone. You may find an additional 2-6” by late Sunday. The heaviest precipitation and strongest winds are expected in the morning, with lighter accumulations later in the day. This new snow fell on a new melt-freeze crust in many areas. This layer should continue to grow thicker and more supportable over the next few days. 

The primary layer of concern in the snowpack remains the mid-January facets/crust. These weak grains sit 6-10’ below the snow surface. A recent snow profile near Crystal Mt on Thursday (03/04) continued to show this layer intact. Very large avalanches occurred 2/26-3/3 near Crystal and one near White Pass. Many of these slides broke large trees and traveled to the bottom of their runouts. Make sure to assess your travel routes with this information in mind. Even though there is not an avalanche problem below treeline,  hazard remains. Avalanches may descend from above and impact travelers at lower elevations. 

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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