Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

Heavy snowfall and strong winds will increase in avalanche danger. You can easily trigger avalanches in steep terrain and might see some natural avalanches as well. Stick to lower-angle, sheltered terrain while the storm runs it's course.

 

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2.5

    It won’t be a day to tip-toe around big slopes. You can assess the instability of new snow layers on small test slopes, but stormy conditions will likely keep you out of most avalanche terrain no matter what you find. Moderate snowfall and strong winds are forecast to last most of the day.

    Don’t ignore obvious signs of instability like whumping, shooting cracks, or recent natural or human-triggered avalanches. You are more likely to trigger a slab in wind-loaded terrain. Drifting snow should show you which slopes are loading up with deeper snow. Strong winds could transport snow and build slabs at low elevations. 

    Convex slopes like this one are where you are more likely to trigger an avalanche in sheltered terrain 

    Photo: Dallas Glass

Avalanche Discussion

The new snow will fall on a variety of surfaces including wind slab, crust, and weak facets depending on aspect, elevation, and exposure to wind and sun. The big question for the weekend is regarding layers of faceted snow at or just below the surface. Will they create bigger, more surprising avalanches?

The coming storm will also bring precipitation with a very strong southerly “flow”. The result is snowfall could vary widely across the zone. South flow-favored locations could see precipitation amounts higher than forecast. Areas closer to the crest should see less. Both Snoqualmie and Stevens Pass are forecast to receive the least new snow of any of the west-side forecast zones. The answer to all of these uncertainties is to start with a simple plan for the day, make good, relevant observations, and err on the side of caution until the storm passes.

A few observations trickled in Friday afternoon from neighboring zones. Some indicated moderate winds were drifting snow and creating fresh slabs up to 12” deep that were easy to trigger on test slopes. At least one was reported as failing at a softer layer above the rain crust.  No wind transport, no signs of instability, and settled powder on shaded slopes were reported from Stevens Pass. Low snow conditions still rule the day at Snoqualmie Pass.

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