Boletín de aludes

East Slopes Central

Northwest Avalanche Center
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Peligro de aludes

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

Lo esencial

Significant snow and strong winds are forecast for Sunday night and Monday. Avalanches may run naturally, and it will be very easy to trigger avalanches large enough to bury or kill you. Avoid travel in avalanche terrain, avoid areas with large snowdrifts, and steer clear of open bowls where avalanches may run from above.

Problemas de aludes

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Very Likely
    Tamaño
    1.5–2.5

    A Pacific Northwest storm with a good fetch of moisture is just beginning to impact our region Sunday evening. This new snow will be falling on various weak surfaces that may easily produce large slab avalanches. These weak surfaces exist at all elevations, and you can likely trigger avalanches in steep terrain, even in sheltered locations at lower elevations. Strong winds will build larger and more dangerous avalanches on lee aspects at upper elevations. Avoid travel in steep terrain on Monday and stick to sheltered low-angle slopes. Avalanches may break surprisingly wide, give extra room for runouts of large avalanche paths in alpine areas. 

    Hand pits and small test slopes can give you excellent feedback about how the new snow is bonding to the existing snow surfaces.  Monday will be a great day to observe red flags indicating unstable snowpack conditions like recent avalanches, shooting cracks, and collapsing. 

    (1/2/2022)

    Example of a shooting crack in new storm snow. This is one of the red flag signs of instability and should drive you to lower angled terrain.

    Photo: Robin Pendery

Avalanche Discussion

A winter storm impacting the region Sunday night will quickly deteriorate current snowpack stability. Up to 1-2 feet of snow may fall in areas throughout the East Central zone. More snow is likely in the Salmon La Sac area and other locations closer to the Cascade Crest. However, even areas far East of the crest, like Mission Ridge, may receive 8-10 inches of snow.

There have been abundant observations of weak snow on the existing surface. Underlaying the weak snow is a variety of surfaces, from sun crusts and wind crusts to soft snow. As a result, adjacent slopes and slight variations in aspect may react very differently to the new snow. We are particularly concerned about steep solar aspects with a few inches of preserved stellar snowflakes, surface hoar, and faceted crystals. On these slopes, avalanches may break farther and become larger than a typical storm slab. 

Mt. Baker, the Chair Peak basin, and Mt. Mastiff have all had avalanches on deeply buried weak layers in the snowpack. These observations seem sporadic and inconsistent, but they indicate uncertainty with the spatial distribution of these deep weak layers. This uncertainty, along with the potentially high consequences of these very large avalanches, warrants extra caution as smaller avalanches may step down to deeper interfaces. 

 

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