Bulletin d’avalanche

East Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Thu
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You can trigger a few different types of avalanches in the recent snow on steep, unsupported slopes. Most commonly, these will be small, predictable, and loose or very soft. If you experience whumpfing collapses, cracks shooting through the snow or strong over weak layering, stick to slopes under 35 degrees to manage this less likely, but more dangerous situation.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    We expect most wind slabs to be small and difficult to trigger. They formed on Sunday, and are now stubborn and buried under more recent snow. To find them, you'll need to probe and feel for stiffer snow under the surface. If in doubt, keep to lower-angle slopes and increase your margin between large, steep slopes.

    While unlikely, there's a chance that you could trigger avalanches in deeper layers in wind-exposed terrain.  If you see cracks shooting away from your equipment or hear whumping collapses, avoid steep rocky features. See more below about a recent Persistent Slab avalanche that was triggered in previously wind loaded terrain.

  • Loose Dry

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    The recent snow is dry, cold, and mostly cohesionless. The frigid temperatures and very light new snow are maintaining these "cold smoke" conditions. The most likely of today's avalanches will be loose and more predictable than slabs. Manage your terrain appropriately by stopping in safe locations, and don't trigger sluff on top of your backcountry partners. 

    Under the new snow there's a widespread layer of weak facets. If you find more cohesive storm snow (perhaps west of the Cascade Crest), you could trigger slab avalanches 1-2 feet deep in the recent snow. They could even be surprising and break widely across terrain. Use quick hand pits and test slopes to see and feel how the new snow reacts.

    (1/31/2025)

    Skiers easily triggered dry loose avalanches like in this photos over the weekend. 

    Photo: Chris Bartram

Avalanche Discussion

A strong storm brought significant precipitation on the 31st-2nd with light accumulation continuing since then. The new snow is very light and cold. The old interface, dubbed "January Drought Layer," is now 1-1.5 feet below the surface. West of the Cascade Crest, you may find even more recent snow. Winds transported snow on the 1st, but have been light since then.

 On Sunday, an NWAC observers investigated an avalanche near the Snagtooth Ridge that was triggered in an old weak layer up to 3ft deep. (See video) The avalanche was triggered at 6,600ft on a northeast aspect from a shallow spot in very steep, rocky terrain. The weak layer was into the lower half of the snowpack and was 1-2mm faceted grains. It's believed that these facets were buried on December 17th. On Monday, an NWAC Forecaster found a similar snowpack structure on northerly aspects adjacent to Silver Star Creek. There, the weak layer wasn't problematic for human triggering. 

The persistent slab avalanche on Snagtooth Ridge that propagated into older, deeper snow layers highlights our complex and variable snowpack.  This could be an isolated incident, but it's probably best to keep it in mind when choosing terrain. Consider avoiding shallow, weak areas in the snowpack, typically found in or near steep, rocky terrain. 

You can help us gather more data by submitting an observation HERE or via the Avy App. 

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