Bollettino valanghe

Stevens Pass

Northwest Avalanche Center
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Wind-drifted snow near and above treeline could catch you by surprise and avalanche with a human trigger on steep slopes. Search for and identify thicker, heavier drifts, and clues like long shooting cracks from your steps, and avoid steep slopes if you encounter these conditions. We may get enough sun that steep, sunny slopes could avalanche as the snow gets moist, running downhill first as pinwheels before possibly flowing as wet loose avalanches. 

 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

     On Saturday small slab avalanches were triggered in wind loaded pockets. You're most likely to find fresh snow drifts along ridgelines, in gullies, and around rocky outcroppings. Wind deposits could react to a human trigger, and depths could vary from 6" to over a foot in depth. Avalanches will probably remain small to medium in size, but a large one isn't out of the question. They may strengthen a bit and become slightly less reactive as the snow settles. 

    Search for signs of instability like long, shooting cracks, whumphs, or recent avalanches. Feel for thicker, heavier snow and scan for textured or wind-features surfaces. Avoid these areas on slopes steeper than 35°. Be especially cautious if you're near terrain traps. 

    Wind slabs like this could fail on steep slopes with a human-trigger on Sunday. This is a small test slope used to determine how reactive the new layer was by stomping at the top with skis. 

    Photo: Irene Henninger

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    The sun could poke out for a little while on Sunday, and this time of year it doesn't take much for wet loose avalanches to start running. Pay attention to sky cover and maintain awareness of snow surfaces beneath you. If snow starts getting sticky and moist, and if you notice rollerballs running from steep slopes, wet loose avalanches could follow.

    Tree bombs or cliffy areas are where you're most likely to see them for starters. This may happen on all aspects at lower elevations, but probably just the southern half of the compass higher up if we do see a bit more sun. Avoid steep slopes in areas where you encounter moist snow and start getting an abundance of rollerballs. 

    Wet loose avalanches could run naturally or with a human trigger on steep slopes if the sun comes out. 

    Photo: Katie Warren

Avalanche Discussion

In most lower elevation areas and the southerly half of the compass a crust exists from the recent high pressure, which the new snow layer could slide on. It could also slide on shallower wind slabs within the new snow. On upper elevation direct northerly slopes a weak layer formed during the high pressure, beneath the new snow layer. This is around a foot deep, and is probably the only area you won't find an obvious crust beneath the new snow. Slab avalanches could be more reactive in these locations. 

In the last week we saw intense springlike high pressure with warm weather for the first time this year, and several days of wet loose avalanches limited to the southern half of the compass. An occasional glide avalanche occurred as well.  On Friday we switched back to winter and we began getting cold dry snow, which we've seen around a foot of since then. A lot of settlement has occurred quickly and the cold dry powder won't last long this time of year. North-facing terrain should hold onto the powder for a few more days. 

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