Boletín de aludes

East Slopes Central

Northwest Avalanche Center
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Peligro de aludes

Tue
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

It may still be possible to trigger avalanches near ridgelines where strong winds deposited snow into deep slabs during the recent storm. The base of cliffs, ridgelines with little vegetation, and alpine bowls at high elevations are the most likely areas to trigger these avalanches. If the snow feels stiff or sounds hollow, stick to lower angle routes or terrain sheltered from the wind. Early season hazards buried just below the surface, like rocks and stumps, can increase the consequences of being caught in even a small avalanche. 

Problemas de aludes

  • Wind Slabs

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

    Winds during Saturday's storm were impressive, and weather stations picked up sustained winds in the 20-30mph range, with stronger gusts. Snow totals varied significantly, with higher totals through the mountain pass corridors. Lake Wenatchee, Holden, and Salmon La Sac picked up 8-10", while Mission Ridge and the Wenatchee mountains only received 3-5". The storm is tapering off, and temperatures are cooling significantly. While this may help to decrease avalanche danger, you could still trigger lingering wind slabs at upper elevations near ridgelines. Wind slabs may be larger in areas closer to the Cascade Crest, which received more snow. These slabs likely formed on variable surfaces, including slick crusts or older weak snow from mid-November, and we have some uncertainty about how easily they can be triggered. With increased uncertainty, it is important to approach new terrain slowly and observe changing conditions as you gain elevation. You can use quick hand pits or your probe/ski pole to feel for stiffer layers of snow over softer layers. Snow that feels stiff, hollow, or cracks shooting away from your feet or equipment are signs you should use low angle routes or move to terrain sheltered from the wind. 

     

    Shooting cracks like these coming from skis, snowshoes, snowmobiles, feet, etc are indicators that reactive slabs exists.

    Photo: Lee Lazzara

Avalanche Discussion

Access to many areas of the eastern Cascades is challenging, and we have limited information about the snowpack. While Saturday's storm may have improved conditions slightly, access at lower elevations is still challenging. If you are headed out into the mountains, be prepared for long approaches on thin snow cover. Many motorized trailheads have limited snowpack, and most have yet to begin grooming operations. In addition, the recent snow may have shallowly buried rocks, stumps, creeks, or other hazards.

Expect frigid temperatures for Monday, with highs in the mid-teens. Bring and wear extra layers and monitor exposed skin for cold injuries. Consider using a buff or face mask to protect your nose and mouth from wind chill. 

Prolonged, cold, dry weather in mid-November transformed snow into weak, angular, sugary snow crystals. During this dry weather, inversion conditions warmed upper elevations, and strong winds drifted this weak snow around. We received many observations of large surface hoar growth in lower elevation locations sheltered from the sun and wind. This layer may be buried 10-20inches deep in some locations. While warm temperatures and rain during the week may have helped to strengthen and round these snow grains, we still have a lot of uncertainty about the extent and distribution of this weak snow layer. Mission Ride Ski Patrol reported that the snowpack is still weak and faceted in and around the ski area. Therefore, when traveling on sheltered northern aspects, it is important to dig down and determine if this persistent weak layer exists beneath the new snow. Avoid traveling on steep terrain if you find a weak sugary layer of snow beneath the storm snow or feel the snowpack collapse beneath you. 

If you are out and about in the mountains, let us know what you find by submitting an observation.

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