Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Stormy weather combined with lingering concerns about several potential weak layers buried in the snowpack deserves a conservative approach Friday. Avoid traveling on open slopes greater than 35 degrees, and limit any time spent in the terrain below. With all the recent snow, any avalanche could grow large and dangerous. 

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Expect moderate snowfall and strong winds to form new and potentially easy to trigger slabs on any open slope greater than 35 degrees. You can observe how the storm snow changes and reacts by using frequent small slope tests and handpits. When you notice failures or see cracking, you likely found the storm slab weakness. Steer around steep open slopes particularly with rocky areas and/or convex rollovers. On southerly slopes, the new snow may accumulate over a thin crust. In these locations, you may experience avalanches fail more easily. 

    Due to the windy nature of this storm, you will find deeper and firmer slabs on wind-exposed slopes at mid and upper elevations. These wind slabs will be most prevalent in areas near Crystal and White Pass. If you see blowing snow, fresh cornices, or drifts behind objects, give the nearby wind-loaded terrain a wide berth. Wind slabs often catch even experienced travelers off guard.

    (2/15/2021) This small Storm Slab was triggered by a skier near White Pass on Monday morning (2/15) as temperatures began to warm. [SW 4700', Cortwright Butte; SS-ASc-R2/D1-N]

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    3

    A lack of confidence in the snowpack stems from the continued presence of several deeply buried persistent layers. Recent observations on these weak grains have been limited due to the stormy weather. This only serves to increase the uncertainty surrounding the ability for these weak layers to produce avalanches. You could trigger a deeper slide from shallow points in the snowpack or if an avalanche steps-down into older snow. Any resulting failure on these deep layers would produce a sizable and destructive avalanche. Consider staying out of larger startzones and limiting your time in the terrain below.

    (2/3/2021) This natural avalanche likely occurred overnight on 02/02 in non-skier compacted terrain within Crystal Mt Ski Area. It failed on 1-2mm facets just above the 1/13 crust. 6300' NNE aspect. 85-95cm deep. Photo: Cyrstal Mt Ski Patrol

Avalanche Discussion

We had a nice ~30hr break in the storms across the West South Wednesday into Thursday. Now, yet another storm should bring 6-12” of snow to most areas by Friday afternoon. This will only serve to maintain or even increase the avalanche danger. Expect the highest avalanche hazard in the morning and during periods of heavier snowfall. 

Recent storms 2/11-2/16 significantly grew the snowpacks at all elevations across the region. This snow sits over a potential weak layer of faceted grains (2/11) that produced wide and surprising avalanches last weekend. While much of the recent snow should have gained strength, questions remain about this lower interface. Deeper in the snowpack still, the mid-January facets and crust continue to linger. It may sit 5 to 8ft or more below the surface in some locations. Due to the depth of this layer, observations have become very difficult. This only adds to our uncertainty. As more snow falls, it should continue to test this deep persistent weakness.

With all the recent snow, expect deep travel conditions. This brings with it the risk for deep snow immersion and tree well hazards. Please follow the link for more information. 

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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