Boletín de aludes

West Slopes North

Northwest Avalanche Center
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Peligro de aludes

Mon
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Avalanche danger could increase with rising freezing levels on Sunday, especially on slopes that face the sun. Avoid travel on and under steep terrain if the snow surface warms dramatically through the day. Watch out for cornices or other unstable snow features in steep or rocky terrain above you.

Problemas de aludes

  • Glide Cracks

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

    Continued glide avalanche activity - plus climbing freezing levels - show the low probability/high consequence threat of glide avalanches is still with us. Look for cracks in steep terrain where the ground surface is visible at the bottom. You can also identify areas of glide where “wrinkles” show the snowpack is slowly slipping on the ground below and could potentially release. 

    Though the danger is higher on sun-warmed slopes at midday, these avalanches can still release at any time. An example of this occurred with cooling temperatures Saturday afternoon on Mt. Herman. Despite being on a shady slope, a chunk of hangfire above a previous glide avalanche naturally triggered. Though small it packed enough punch to seriously injure. Give suspect areas plenty of room and minimize the amount of time spent below if there are no other terrain options.

    (1/15/2022)

    Detail of glide avalanche in hangfire of a previous avalanche.  Mt. Herman - E aspect at ~4300'

    Photo: Jason Speer

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    Loose wet avalanches are possible on southerly slopes on Sunday. The likelihood is highest above treeline where dry surface snow will be more susceptible to warming. Rising freezing levels plus the probability of more sun will require you to assess danger based on changing conditions. Move to lower angle terrain if you witness signs of instability like rollerballs, a rapidly warming snow surface, or current avalanche activity. If you find a thick crust topping snow surfaces, then loose wet avalanches are unlikely. 

    A natural wet loose avalanche (D1.5) on a sun-exposed slope.

    Photo: Zack McGill 

Avalanche Discussion

The North Cascades are currently in a pattern of daily warming and cooling reminiscent of a spring diurnal cycle. The difference is long January nights have so far allowed the snow surface to refreeze despite partial cloud cover and above freezing temperatures. The outcome is still the same:  lower avalanche danger first thing in the morning,  then increasing through the day in relation to freezing levels and cloud cover.

The snowpack is currently capped with a ski supportable melt-freeze crust near treeline. Below are alternating layers of wet rounded grains and melt forms down to another crust. The latter formed near treeline from rain between periods of snowfall on January 6th. The upper and mid snowpack is generally strong and well bonded except where melting is undermining strength.

Wind transport of dry snow was observed at the highest elevations on Friday. If you make it to the alpine be on the lookout for small but unstable wind slabs in exposed terrain.

Excellent visibility Friday and Saturday allowed for observations throughout the zone. Glide avalanches, cornice fall triggered slab avalanches, loose wet, wet slab, and a very, very large slab avalanche high on Mt. Shuskan were reported. All were triggered during periods of warm temperatures and heavy precipitation earlier in the week. 

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