Bulletin d’avalanche

East Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Thu
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Points saillants

A deluge of rain is expected to create very dangerous avalanche conditions on Wednesday. The mountains are in full melt-down mode with avalanches running on the ground in form of deep wet slabs and glide slabs. Stay off of and out from underneath steep slopes while these conditions continue. 

Problèmes avalancheux

  • Wet Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    2–3

    A prolonged period of warm and wet weather, combined with a weak snowpack structure have created unique conditions for scary wet slab avalanches. These are running on old faceted and crust layers from December, and/or on the ground. What does this mean? It means slides may fracture widely across terrain features, and carry the entire seasons snowpack with it. Slides may be 2-4ft deep, and could be powerful enough to take out trees. Along with these nasty slides, wet loose avalanches may run and scour to the ground, cornices may break and trigger avalanches, slush flows, and rock/landslides may occur. 

    Stay off of, and out from underneath steep slopes on Wednesday. 

    (1/28/2024)

    Very Large wet avalanche that ran naturally on 1/28 in the Icicle River Drainage.

    Photo: Erik Soldenwagner

  • Glide Cracks

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

    Heavy rain should start running through and underneath the snowpack. Glide activity has increased over the past 24 hours, and may pick up again on Wednesday. These types of avalanches are not something we talk about too much in this zone, but on Wednesday we could see a cycle of them. Typically glide slabs run on smooth bedsurfaces, like rocks and grass. Large, complex terrain features can funnel slides into gullies. Stay away from these runout zones while its raining heavily or if you see glide cracks. 

    (1/30/2024)

    Glide avalanches that entrained wet snow. E at 3,000ft in Tumwater Canyon.

    Photo: Matt Primomo

Avalanche Discussion

Although we may have hit a peak of instability on Sunday, water hasn't necessarily made it all the way through at upper elevations, and areas near the crest where the snowpack is deeper. On Wednesday, it might. This is particulary concerning because this 'wetting front' is likely to reach our persistent weak layers in the lower third of the snowpack, and we'll be receiving heavy rain at the same time. These two things combined could create another widespread, natural avalanche event. 

On Sunday, Monday and Tuesday, many natural and skier-triggered, very large avalanches (D2.5-3) were reported throughout the zone and in neighboring zones. Control at Stevens Pass ski area on Tuesday triggered very large (D3) avalanches that ran on the Solstice Crust. On Sunday, an avalanche running on the Solstice Crust and gouging down to the ground at Mission Ridge indicated that these deeper, weak layers are active there. So now we know that slides are quite possible on this layer within the entire zone from west to east. With scary, hard-to-predict avalanches, the take-home point is that until the snowpack experiences below-freezing temperatures, the potential for various types of wet avalanches remains. 

Faceted snow over the Solstice Crust was the persistent weak layer involved in multiple skier-triggered avalanches earlier in January, and activity on this layer only increased as temperatures warmed. When it began to rain, reports of very large avalanches running on deeply buried weak layers came in from nearly every zone in our forecast area. The overall weak structure of our snowpack has led to the current prolonged period of instability. With an entrenchment mindset, practice patience and only travel in the mountains if you are confident in your ability to avoid avalanche terrain and runout zones. 

If you get out, let us know what you see by submitting a public observation!

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