Boletín de aludes

West Slopes South

Northwest Avalanche Center
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Peligro de aludes

Sun
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 6 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Pay attention to wind-affected snow at all elevations. If you see blowing snow or fresh cornices, steer around nearby steep slopes and seek out more sheltered terrain. Uncertainty about deeper layers in the snowpack should give you pause before you enter large avalanche paths.

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    Watch for new and potentially easy to trigger slabs in wind drifted snow at any elevation. As the winds increase Saturday, you may see blowing snow to help you identify which aspects and features could hold wind slabs. Fresh cornices and drifts behind objects may also point toward wind-loaded areas. These slabs may grow deeper and more widespread as the day continues. If you suspect a steep slope is wind-loaded, steer around it and seek out lower angled or more sheltered terrain. 

    On the volcanoes, just because you’re out of the wind doesn’t mean you’re out of harm’s way. These sites should receive enough new snow to form shallow storm slabs. Use caution near convex rollover and in very steep terrain where you may trigger one of these relatively shallow storm snow layers. 

    (2/19/2021) Cornices and drifts like these along the ridgeline of East Peak (Crystal backcountry) can help you identify wind-loaded slopes below.

  • Deep Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    3

    NWAC staff targeted observations on several persistent weaklayers in the snowpack near Crystal Mt on Friday. Snow profiles and snowpack tests continued to highlight the 2/11 and mid-January layers. While triggering an avalanche on these older weak grains seems unlikely they could produce a very large and dangerous slide. Take these consequences into account when choosing your terrain for the day. Consider staying out of large startzones and limiting your exposure on slopes below. You may initiate a deep avalanche from a thin spot in the snowpack or if a smaller slide steps-down into older snow layers.

    (2/19/2021) This snow profile shows two buried older weak layers in the snowpack. The mid-January layer sits more than 4' below the surface in this location. NE, 6200' Cement Basin. Crystal backcountry.

Avalanche Discussion

Many locations around the West South zone received 4-8” snow Thursday into Friday. Moderate to strong winds during this period limited the development of storm slabs for most locations. With an additional 3-6” of snow and continued windy conditions expected through Saturday, this should help maintain dangerous avalanche conditions at mid and upper elevations. 

We’re in the middle of a very active weather period stretching for nearly 3 straight weeks. Snowpacks across the zone continue to grow. Hiding in all this recent snow sit two prominent weak layers. The 2/11 interface (down 2.5-4’) produces several surprising avalanches last weekend. You may find well-preserved stellars or facets at this interface. Deeper in the snowpack (4-8’), the prominent mid-January crust/facet layer continues to linger in locations above 5000’. Recent snow profiles and snowpack tests show little change in the faceted grains, but test results are becoming less consistent. However, the recent storm weather limited our ability to make observations on this layer and a significant amount of uncertainty remains. 

With all the recent snow, tree well and deep snow hazards exist. Please follow this link for more information. 

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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