Boletín de aludes

West Slopes South

Northwest Avalanche Center
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Peligro de aludes

Fri
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Newly formed wind slabs in all areas of the West South could produce avalanches on Thursday. Look for visual clues like drifts and cornices to help identify where the wind deposited snow. Steer around these steep wind-loaded areas and seek out less wind-affected terrain. 

Problemas de aludes

  • Wind Slabs

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

    Moderate to strong westerly winds during this storm likely formed slabs on the lee sides of ridges and exposed features at all elevations. Since the storm just ended Wednesday night, give these fresh wind slabs time to gain strength. Look for clues like textured snow surfaces, drifts, and sharp cornices to help identity which slopes may hold potential avalanches. When you see these clues, steer around similar wind loaded areas and seek out lower angled or less wind-affected terrain. If you find evidence of wind slabs on exposed features at lower elevations, these slabs will only grow deeper, more wide-spread, and possibly easier to trigger as you ascend. 

    While we expect most of the hazard to exist in the wind drifted snow, you may still encounter lingering storm slabs. These are most likely in locations that received more snow like Paradise and Mt St Helens. If you find 10” or more of recent snow, be leery of any steep open area. Use small slopes and hand pits to observe the upper snowpack and test for layers that could fail and produce avalanches.

    (3/20/2021) Using visual clues is a great way to help identify the potential for Wind Slabs.

Avalanche Discussion

Storm totals as of Wednesday afternoon range from 4-10” around the West South zone. Continued snow showers could add an additional 3-5” before Thursday morning. This new snow sits above our most recent interface (3/24). Prior to this storm, a wide variety of snow surfaces were observed including firm crusts, weak snow, and well settled powder. As a result, you may find that the new snow reacts very differently from slope to slope. This could keep you on your toes. Don’t expect observations from one slope or area to apply widely to other terrain where you travel. Despite all this variability, we anticipate any avalanche hazard to remain at or above the 3/24 interface. 

Thursday’s transitional weather from a cool winter storm to a warmer spring-like pattern can be tricky. We anticipate cloudy to mostly cloudy skies during the day. If you experience more sunshine, you could see a loose wet avalanche hazard develop. With the strong March sun, this may not necessitate full sunshine. Thinning clouds and “greenhousing” may be all that’s needed. If you start to see the snow shed from trees or notice a wet sticky snow surface, start to anticipate natural loose wet avalanches. Steer around steep sunny slopes when you see new rollerballs or find fresh fan-shaped debris. 

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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