Lawinenlagebericht

West Slopes South

Northwest Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
3 · Erheblich
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Veraltet — dieser Lagebericht ist 6 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Dangerous avalanche conditions will exist across the zone on Wednesday with larger snow totals on the volcanoes. Unsupported slopes, terrain features steeper than 35 degrees, and any slopes with evidence of wind-drifted snow have a higher likelihood of avalanches and should be avoided. If you find that the new snow has not bonded well to the old snow surface, avoid all slopes where avalanches can run or stop.

Lawinenprobleme

  • Storm Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    1–2

    Look for Storm Slabs to develop in all parts of the zone and at all elevations on Wednesday as stormy weather returns. These slabs may be more reactive in areas where the wind is able to move any freshly fallen snow around to create deeper and stiffer slabs on leeward slopes, at the base of cliffs, or on the sides of gullies. These avalanches generally trigger more easily on slopes steeper than 35 degrees, convexities, and unsupported slopes. Take the time to dig some hand-pits and play on small test slopes to give yourself an indication of how sensitive slabs may be and what their bonding is like. If you find that the snow is poorly bonded to the old snow surface or has sensitive interstorm layers, seek out terrain less than 35 degrees. Shooting cracks, collapses, and recent avalanches are obvious signs of instability that should give you pause. 

    (12/16/2020) Skin track test showing cracking in the surface snow. This can indicate storm slabs are present.

Avalanche Discussion

The volcanoes should out-produce areas closer to the crest during this storm, but avalanche hazard may not be that different across the zone. All areas are set to receive a good shot of precipitation and Storm Slabs should exist at all locations with slabs being larger and possibly more reactive on the volcanoes. If Paradise happens to exceed its water numbers,  very dangerous avalanche conditions could exist, and travel in avalanche terrain is not recommended. 

Prior to this storm, the snowpack around the West South generally contained an average of 20-35cm of snow sitting over a stout crust (12/21). We saw multiple human triggered avalanches occur in this snow recently, some of them large and breaking in surprising ways. As we prepare for new snow Tuesday night and Wednesday, keep these recent avalanches and our previous snowpack setup in the back of your mind. On Tuesday, professionals around the zone reported weak snow grains on the surface at Crystal, White Pass, and Paradise. It remains to be seen if these grains persist and get buried once the storm hits. If so, avalanches could break in surprising ways or propagate long distances. The most likely scenario is that avalanches will fail at the old/new snow interface on Wednesday, but there remains the possibility that with enough of a rapid load, previous layers could become activated and produce larger avalanches (down to the 12/21).

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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