Boletín de aludes

Olympics

Northwest Avalanche Center
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Peligro de aludes

Sat
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

Snow drifting over a weaker old snow interface or exposed crust may surprise you on Friday.  Active wind transport, fresh wind lips, cracking snow surfaces, and probing can help you identify and steer around drifts 6" or deeper that will be reactive on slopes steeper than 35 degrees. 

Problemas de aludes

  • Wind Slabs

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

    Gusty and swirling winds easily transported around 4" of snow near and above treeline on Thursday. We're expecting another 1-2" of snowfall Thursday night with just enough wind to redistribute it. Slabs continue to form atop a faceting old snow interface and in isolated areas on an icy 2/13 crust.  A small natural wind slab below a corniced ridgeline (a frequent flyer) highlights the potentially touchy nature of these fresh slabs. These are the sort of specific features where you might expect human-triggered avalanches on Friday along with unsupported terrain features in alpine bowls, potentially well below the scoured ridgelines.

    (2/16/2023)

    Small natural wind slab in center of photo. North Bowl, N aspect at 5200 ft.

    Photo: Sam Siemens-Luthy

Avalanche Discussion

4-5" of low-density, right-side-up, and faceting snow sits above the 2/13 crust complex.  Winds were effectively redistributing the snow (see video) into drifts up to 15" deep on Thursday, while isolated slopes were scoured to ice. Ridgelines were scoured bare in many places while trees had lost most of their snow. AlThe 2/13 crust complex has a breakable 1 cm upper crust, 2 cm of faceting dense snow, and a 2 cm fully supportable lower crust.  This faceted sandwich could come into play in a future loading event. The 2/3 crust/facet sits 35 inches or more below the snow surface. Avalanche professionals continue to get some reactivity in test results under this crust, but it is not currently a concern for human-triggered avalanches given the thickness of the 2/13 crusts.

1-2" of snow may improve ski quality by Friday. Continue to pay attention to the drifts of snow above the 2/13 crust complex, but also watch for shallowly buried obstacles, particularly near ridgelines.

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