Boletín de aludes

West Slopes North

Northwest Avalanche Center
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Peligro de aludes

Tue
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

Slab avalanches are likely as snowfall continues through Sunday night. Expect the most reactivity in mid to upper elevation wind affected areas, however avalanches may occur on other steep slopes as well. Stay off terrain steeper than 35 degrees, especially where you identify wind loading.

Problemas de aludes

  • Storm Slabs

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

    Several reports of human triggered avalanches came in over the weekend.  HERE and HERE are observations of skier triggered soft slab avalanches in the Iceberg Trees, failing in the storm snow on Saturday. THIS observation from the Bagley Lakes area on Sunday shares a concern for unstable conditions with the previous days’ observations. Sunday night another 6 inches to a foot of new snow will fall, keeping the avalanche danger elevated. 

    You will find the most avalanche activity in mid to upper elevation areas where there was wind loading. Avalanches could break within layers of new or wind drifted snow, or on variable old snow surfaces buried Thursday (3/18). Small dry loose avalanches also may run on the surface of steep slopes.  Pay attention to the layer beneath the new snow, as melt freeze crusts were present before the storm on the southerly half, while direct northerly aspects above approximately 4500ft held dry snow. Weak snow may have formed at the surface of the dry snow during the high pressure over the last week, so failures may occur easily at that interface.

    Dig down to the new snow/old snow break to investigate how readily snow slides at the interface, or on layers within the new snow. Seek out small slopes before committing to larger terrain. Avoid slopes steeper than 35 degrees, especially if there are signs of wind loading.

    (3/21/2021) A human triggered slab avalanche on Sunday in the Horseshoe heading to Elf Chutes. The avalanche was about a foot deep. Photo: Adam U

Avalanche Discussion

As of writing this forecast, 27 inches of snow was recorded at the Heather Meadows weather station since 3/18. Several more inches are falling overnight. Our avalanche problems are limited to new snow, but this is an impressive amount, totalling around 3 feet in non-wind affected areas on Monday. It is a welcome reprieve to be back to winter conditions, but avalanche risks are elevated with the return to winter. Keep this in mind as you enjoy the fresh powder. 

Cornices are continuing to increase in size and weight. They could drop onto slopes below acting as huge triggers. Stand back from cornices along ridgelines and minimize overhead exposure to these features. Several large glide cracks and a few glide avalanches were observed recently as well. Cooling temperatures should limit glide activity for now, but these avalanches are difficult to predict. If you notice crevasse-like cracks in the snowpack, avoid slopes beneath those features.

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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