Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 5 months ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

There has been a lot of snow this past week. A LOT! It will take time for all the new snow to heal. While avalanches could occur on any steep open slope, they will be more likely on convex rollovers, in complex terrain, and in wind loaded areas.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–2.5

    Snoqualmie Pass received 5-6 feet of snow at middle and upper elevations during this storm cycle. Changes in temperatures, precipitation rate, and winds left several interstorm layers in the upper snowpack. While the new snow seems to be gaining strength, sometimes this takes time. As it does so, avalanches may become harder to trigger, but not impossible. 

    Often, the problem lingers the longest in very steep terrain and areas where the wind built firmer and thicker slabs. What’s tricky is that with so much new snow, we can’t rely on our normal hand pits, uptrack tests, and small slopes to give us reliable information. Instead, we’re stuck just being patient. Treed terrain and smaller slopes offer the best chance at enjoying the new snow safely. 

    Even if it’s hard to say how likely you are to trigger a storm slab, one thing that is more certain is the size. With all the new snow, avalanches have the potential to grow large and deadly. These aren’t a version of storm slab you want to tango with.

Avalanche Discussion

Well, that was a good run! Near constant storms starting on 3/8 finally ended early Saturday morning, but not before bringing nearly 8 inches of precipitation, totaling 50-70 inches of snow, and generally doubling the snow depth. Clouds parted, and the sun came out on Saturday, helping the new snow settle and building a thin crust on southerly aspects. 

Our next weather system starts to arrive on Sunday, first with clouds and slowly rising temperatures, and then eventually precipitation. Unfortunately, this one is much warmer, and rain will start reaching into the middle and upper elevations. Sunday night, the storm should ramp up, and the avalanche danger could rise quickly. This might not be a good night to go camping. Natural avalanches could become common as the rain intensifies. 

Within all the new snow, there are two prominent layers that act as snowpack markers and are worth keeping an eye on. The 3/12 crust is generally about 3 feet (90cm) below the surface. This layer may have been the culprit in many of the natural and triggered avalanches reported on Friday. At the base of the new snow is the 3/8 crust. You’ll need your probe to find this one, often about 4 feet (120cm) below the surface.

With so much new snow, deep snow immersion can be a real hazard. You can learn more about deep snow safety here.

It's certainly nice to see winter roar back! However, keep in mind this was a big change to the snowpack, and we’re still ‘digging out.’ Information has been limited. We don’t have the same level of confidence after multiday storms like these. 

Régions couvertes