Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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2 · Moderato
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1 · Debole
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In sintesi

The likelihood of wet avalanches may increase with higher freezing levels, especially on slopes that face the sun. Stay out from under cornices, unstable snow blocks and slabs hanging in rugged terrain, and other overhead hazards.

Problemi valanghivi

  • Glide Cracks

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    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 glide avalanche.  Mt. Herman (West North) - E aspect at ~4300'

    Photo: Jason Speer

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    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. 

    (4/14/2021) A large glide crack, a glide avalanche and several small wet loose avalanches in the Mountain Loop Highway area. Photo: George Coiner 

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 extensive observations in the adjacent zones. 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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