Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 8 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Snowfall and avalanche activity haven't been as productive in the last few days as we expected, but cooling temperatures and more snow will drop snowlines to lower elevations, increasing the risk of large, human-triggered avalanches. Wind-drifted snow is the main concern, with danger rising as you gain elevation and as the day progresses. In areas with drifts over 6 inches, stay in sheltered, lower-angle terrain and avoid steep slopes.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2

    It's likely that you could trigger a large slab avalanche that can kill you at mid and upper elevations. Wind slabs will increase in size as you climb higher and as the day progresses, and snow continues to fall. Even at lower elevations, by the end of the day, there could be 6 or more inches of new snow over the old, wet, crusty layer. 

    We expect the snow in non wind-loaded areas will be less reactive, since the new layer will probably be bonded well to the underlying wet surface, and cooling temperatures will create a more stable "right side up" effect. However, in areas where the wind drifts snow into thicker, heavier slabs, these drifts are likely to avalanche with a human trigger. Natural avalanches are possible.

    Search for clues while you travel, like long shooting cracks from your steps or sled. Identify actively blowing snow and see where it's landing. Drifts commonly form around rocky outcroppings and features, in gullies, and along ridgelines. You can dig hand pits down to the old snow and see how easily snow slides on the underlying layer. Steer around steep slopes where you identify drifted snow, and stick to lower-angle terrain. 

    Example photo: Wind transport creates obvious cornices. It' may not be as easy to see new wind slabs building up on slopes beneath the cornice, but expect them to be there. 

Avalanche Discussion

There's a chance that the forecast might be off, like it was for the last couple days.  But we've got better certainty in the weather forecast: we'll be receiving a healthy serving of snow Saturday night and Sunday, and temperatures will actually be dropping a bit more. Nevertheless, it's always up to you to check conditions as you travel and make adjustments as needed. 

Forecasts call for 6-8 inches overnight and another 6-10 inches during the day, with enough wind to redistribute the snow. Snowlines are shifting from the top of the lower elevation band overnight and then further down into lower elevations during the day on Sunday. There's a chance that, given the previously warm weather, all the new snow will stay plastered in place and won't be as reactive, but it's hard to tell beforehand. Be sure to evaluate this as you travel. When in doubt, stick to lower-angle terrain. 

Observers from the last few days found semi-supportable wet crusts up through mid elevations. Varying amounts of wet avalanche activity happened, although a good chunk of it was limited to rollerballs. A few glide cracks popped up in the last few days, and they may still be active as temperatures are just beginning to cool on Sunday. Consider giving the area beneath gaping glide cracks a wide berth. 

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