Boletín de aludes

West Slopes South

Northwest Avalanche Center
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Peligro de aludes

Wed
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

You’re more likely to trigger an avalanche in wind-drifted snow at mid-elevations on Tuesday. If you encounter wind-stiffened snow that feels hollow, you should retreat back the way you came and choose another route. Recent human-triggered avalanches in the southern part of the zone should have you thinking critically about a slope before committing yourself.

Problemas de aludes

  • Wind Slabs

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

    Wind-loaded features will continue to be of concern for triggering an avalanche on Tuesday. You may need to find the sweet spot where the wind was blowing recently, but there was enough sheltering that the snow was able to drift and accumulate. We have received reports of Hard Slabs being triggered two days in a row now from different areas of the zone (more in the discussion). Hard Wind Slabs are a tricky problem to manage. You can still look for areas that look “fat” or have textured surfaces, but they will also be firm and may feel hollow. These slabs can break in unpredictable ways, sometimes above you or after several people have crossed a slope. In some locations, they may be sitting on a crust, providing a good bed surface for them to fail and run on. If you suspect a slope is wind-loaded, it’s best to just steer around it for the time being while we give this tricky avalanche problem more time to heal. 

Avalanche Discussion

On Monday, NWAC forecasters met up at Mount St. Helens to get some information from the southern end of our zone. They found that the mountain had been severely impacted by this weekend’s windy weather, with a variety of surfaces and upper elevations scoured down to a firm layer. At mid-elevations, they easily triggered multiple wind-loaded pockets on test slopes and came across one large natural avalanche (HS-N-D2-R2-I SSW 4500’) that had failed within the last 24 hours. They also unintentionally triggered a large Wind Slab avalanche (HS-ASu-R2-D2-I S 4000') 150 feet wide with a crown up to 3 feet in depth. This Hard Slab failed on the 1/21 interface about 1.5 feet below the surface. No one was caught or carried but it definitely surprised them, highlighting the unpredictable nature of these types of slides.

This observation comes a day after we received a similar report from White Pass. Upper elevations had been scoured, but closer to the more sheltered trees, Hard Slabs were reactive to human triggers on specific terrain features. Over at Mount Rainier, observations indicate that there are wind-scoured firm surfaces up high, with variable wind-effected surfaces such as wind-board and breakable crust at mid-elevations. In sheltered areas, you can likely still find well-settled powder. Some groups reported seeing small pockets of Wind Slab being triggered during their travels on Sunday. 

While our focus remains on the recent storm snow, we still have our eyes on older layers in the snowpack - 1/27, 1/21, 1/18, and MLK crust. These interfaces have shown some signs of weakening in recent days but we don’t have many concerns about them being activated until we get back into a more snowy regime. 

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