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 6 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Expect very dangerous avalanche conditions as a hefty up-slope storm affects the area. People could trigger surprisingly deep and wide avalanches as low as 4,500ft, some on old snow layers. Loose dry avalanches may run during the day. Avoid going on, or under steep open slopes as well as sparsely treed terrain at all-elevations during this prolonged storm cycle.

Problemas de aludes

  • Storm Slabs

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

    On Sunday, the new snow was 'right side up' as it finished with a  cooling trend. The storm on tap for Monday probably won't be that way. There are a number of potential weak layers to be concerned about, so it will be best to stay off of, and out from underneath steep slopes. Look for shooting cracks and other signs of instability such as whumphing collapses or recent avalanches. In areas exposed to the wind, thicker and more cohesive avalanches may run. Avoid open slopes steeper than 30 degrees, and be aware of what is above you. Cornices may easily break off and trigger avalanches on the slopes below as well.

    A 240ft wide avalanche was triggered by a skier from a distance at 4,700ft on a South aspect in the Salmon la Sac on Saturday. Another 200ft wide avalanche was triggered by a snowmobile side-hilling on a SW aspect of Round Mountain on Saturday. These were both about 1.5-2ft deep, and may have run on a recent suncrust.  Additional observations report shallow wind slabs releasing near Mission Ridge, and Salmon la Sac on NYE.  These avalanches may only be deeper and wider on Monday. 

    With all the deep new snow, loose dry avalanches may run easily on Monday. Look for these fan-shaped slides that start from a point (also known as point releases). In big, steep terrain these could entrain lots of snow, and create large avalanches. 

     

    (1/2/2021) A 240ft wide, 1.5-2ft deep avalanche triggered from a distance by a skier on Saturday 1/2. South aspect at 4,700ft in the Salmon la Sac.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–3

    Heads up, persistent slab avalanches may begin to 'wake up' during this heavy storm load. A weak layer of sugary snow sits atop an icy crust from early December. Keep your distance from slopes 35 degrees and steeper that are open enough and tall enough to produce large avalanches. Watch for obvious signs of instability like recent avalanches, whumphing collapses, or cracks shooting through the snow. The next couple of days will be a good time to stay off of steep, open slopes as the storms continue to stress these deep weak layers. The most dangerous slopes will be steep, open starting zones. Mid elevation, unsuspecting slopes in sparse trees are candidates for these deep avalanches as well.

    Weak snow above a crust is a tricky and historically deadly weak layer east of the crest. This structure may be anywhere from 1.5ft to 4+ft below the surface, above roughly 5,000ft. In the southern half of the zone, a few potential crust layers exist. In the northern half, weak snow above a crust from early December is more concerning, as the 12/21 crust did not form there. In the Wenatchee Mountains, there is growing potential for avalanches to run on weak snow near the ground.   

    (12/29/2020) Very large persistent slab avalanche off the East Face of Rampart Mountain i the Entiat Drainage.

Avalanche Discussion

This storm should be a good one for the east slopes, including the Wenatchee Mountains. This part of the range hasn't seen a good upslope storm like this for some time, and the snowpack is generally shallow and weak. Very deep snow was found on Sunday in the Icicle Creek drainage, where a cycle of large loose avalanches ran recently. A D2.5 avalanche was observed from Slide Creek in Icicle Creek. Near and above treeline, intense wind loading was occurring during the day, and formed stiffer slabs. Monday could be very dangerous as another potent storm delivers more snowfall to the area.

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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