Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

Dangerous avalanche conditions exist, and triggering an avalanche is likely. Your main concerns exist in the new snow that's fallen since Sunday, which could be around a foot or more, as the peak instability of larger, deeper avalanches is probably behind us. Avoid travel on steep slopes where new snow amounts are about 6 inches or greater, and especially in areas where snow drifts into thicker, heavier deposits, or in areas where you're sinking several inches into wet, heavy snow. 

Problemi valanghivi

  • Storm Slabs

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

    You're most likely to trigger an avalanche in the new snow layer that sits over the older wet layer. Snow falling Sunday night and more on Monday could amount to between 6 inches to over a foot of new snow that could avalanche. Even the upper portion of the lower elevation band has enough new snow for the problem to present a concern in the lower elevation band. 

    An increase in temperature during the day could make new storm slabs more reactive to a human trigger as the day progresses. Wind speeds will also be strong at times, and you can expect massive amounts of snow redistribution. In areas with thicker drifts, triggering an avalanche will be more likely. Natural avalanches could also result. Nevertheless, expect instability on all aspects, wind-loaded or not.

    On Monday, avoid slopes greater than 35° and choose sheltered, lower-angle terrain. If you see any natural avalanche activity, avoid travel beneath large, steep slopes as well. 

    (12/24/2024)

    Example photo: A storm slab avalanche, similar to one that you might be able to trigger on Monday. 

    Photo: Katie Warren

  • Loose Wet

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

    The lower elevation snowpack may have a couple of inches of new snow over the old, wet layer. This snow is what you're most likely to trigger an avalanche, or see natural activity on. As you travel higher, nearing the mid-elevation band, more snow sits over the old, previously saturated layer and may avalanche as temperatures increase during the day. 

    If you find moist or sticky new snow, search for natural activity like rollerballs or small, wet slides fanning out. As the day progresses and warms, more avalanches may result. Likewise, you may be able to trigger one of these avalanches on a steep slope. Beware of small amounts of snow entraining more as they slide downhill, which could result in a larger and more dangerous slide. Avoid travel on steep slopes where you see any activity and terrain beneath these steep slopes as well.

    (2/17/2025)

    Wet loose avalanches like these ones could occur on Monday. 

    Photo: Roman Pavenko

Avalanche Discussion

We suspect most natural avalanche activity occurred Saturday and Saturday night, when peak precipitation occurred. The neighboring West North zone reported many large, D2-2.5 avalanches, and a few were very large, D3-3.5 avalanches stepping down into deeper, old layers and running full path. Stevens Pass had natural wet avalanche activity overnight and at the start of the day on Sunday as precipitation backed off. The old snow's top foot or more is a wet, mushy layer, and appears to have adjusted to the wetting. Deeper avalanche concerns have likely subsided in our zone.

Weather stations around the zone reported 3-5" of water since Friday. The last bit of it arrived as snow early Sunday morning. Over the next several days, expect to receive more precipitation, and warming temperatures looking further into the week. 

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