Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Sat
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You may find pockets of unstable snow lingering on wind loaded slopes in shaded terrain. The tricky part is a few inches of recent snow may hide some of these slabs from view. If you feel firm or hollow snow underneath you, seek out lower angle slopes to avoid the problem.

Problèmes avalancheux

  • Wind Slabs

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

    Two very different wind slab problems could play out on Friday. The trickiest issue comes from older hard slabs formed on Tuesday. Observations found some of these pockets sit on top of very weak facets and continue to produce shooting cracks. A few inches of recent snow could make seeing these slabs difficult. So, the feel of the snow may be the easiest way to locate them. If you find firm (but not icy) and hollow snow underneath you, it’s likely one of these older wind slabs. They often occur on NW-N-NE aspects at mid and upper elevations. Hard slabs can be tough to assess. While they may seem stable, they frequently surprise travelers by breaking above them or after others have crossed the slope. 

    The second concern could arise from increasing winds drifting the light surface snow into new shallow slabs. This problem will be much easier to witness and avoid. Blowing snow and smooth pillow-like drifts will highlight steep slopes you may want to avoid. In both cases, we expect these potential avalanches to be rather small, but they can still harm you if they push you off a cliff or into rocks.

    (3/9/2022)

    Avalanche professionals reported a few shooting cracks in wind-loaded pockets on northerly terrain on 3/9.

    Photo: Shane Robinson

Avalanche Discussion

Relatively quiet weather since the start of March created a rather aspect and elevationally dependent snowpack.

Lower Elevations: No matter the aspect, variable conditions exist. Very firm, rough, and occasionally icy surfaces make travel challenging. The upper snowpack typically consists of stout crusts with pockets of weaker snow. However, the variability across a single slope keeps most of these layers from being a concern. Piles of frozen avalanche debris and open creeks add to the difficulties you may encounter. 

Mid and Upper Elevations:

Southerly Aspects: A breakable sun crust formed on many steep sunny slopes over the past few days. This crust is separated from the underlying thick and strong atmospheric river layer by a few inches of recent snow (3/8). Northerly Aspects: Cold dry unconsolidated snow from a series of small storms since March 2 covers most surfaces. The most recent (3/8) brough around 4” of snow to the Pass. This storm snow caps a layer of very weak and well developed facets (1-1.5mm) sitting on the atmospheric river crust. Outside of wind affected areas, there currently isn’t a slab over this possible weak layer. However, we are monitoring these persistent grains as we head into a more active weather pattern this weekend. 

The crust formed by the atmospheric river (2/28-3/1) is very thick and strong. We currently do not have any layers of concern below this crust.

Régions couvertes