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

Warming temperatures may lead to moistening snow surfaces, and loose avalanches may run on steep slopes in the sun. You could still get surprised by triggering a persistent slab 2-3ft deep at mid and upper elevations.  Look for simpler, less steep, and more supported terrain while these dragons linger.

Problèmes avalancheux

  • Loose Wet

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

    Direct sun and warm temperatures may create wet loose instability on steep slopes. You can anticipate this problem by considering your aspect vs. timing of when you might be on any given slope. Look for signs of instability, like small rollers falling out of trees or small fan shaped slides. Feel for moistening snow surfaces on slopes in the sun. You can use test slopes to check and see how any given area might react. These slides should remain small, but may be able to entrain more than you'd think, especially in larger terrain features. 

    Example medium sized wet loose avalanche.

    Photo: Matt Primomo

  • Persistent Slabs

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

    Observers have been reporting numerous large and very large avalanches that failed and ran on deeply buried weak layers. Put a larger buffer of terrain between your group and large start zones or complex avalanche paths above 6,500ft. Choose smaller, well-supported slopes and stay well out from under larger features. Signs of instability can be inconsistent, creating a tricky problem that is essentially 'unmanageable'. You might not receive signs of instability before the whole slope fails. It could be the 2nd, 3rd, or 8th person on the slope that triggers it. A layer of surface hoar and facets were buried on 2/24, as was faceted snow over a strong crust from late January. You could find these two layers 1.5-3ft down and 2-4ft down respectively. These rest under a hefty new snow load, and have been the culprit of numerous close calls and one fatality in the eastern Cascades.  

    A very large avalanche was triggered by skiers on 3/2 on Kangaroo Ridge. This broke very widely and ran almost the entire length of the path. 

    Pk 8183, WNW, 7,600ft

    (3/2/2024) Photo: Willie Webster

Avalanche Discussion

Wednesday should be another beautiful, sunny day in the mountains. The strengthening March sun may begin to have more of an affect on snow surfaces, especially those steep slopes that face SE-SW. Continue to keep your slope angles mellow while the persistent slab adjusts over time. 

On Tuesday, a few small wet loose avalanches were reported, and a few small wind slabs were triggered by skiers on higher elevation slopes. An NWAC forecaster found a variable structure at a crown profile of the avalanche on Big Kangaroo. Signs of instability have been quieting down, but were abundant this past week following a large storm. Multiple close calls and numerous snowpack observations in the Highway 20 corridor point to a couple of buried weak layers (2/25 and 1/31) in the top 2-4 feet of the snowpack. On Saturday, an NWAC observer witnessed a group trigger a widely breaking, very large avalanche on Big Kangaroo. It ran almost the entire length of the avalanche path. More details on the Kangaroo Ridge avalanche can be found in the photo caption below, in this observation, and Josh's ob here. In a sepereate event on the southeast sholder of Cutthroat Peak (6,400ft, SE) a party remotely triggered avalanches that propagated to either side of them 800-1000ft after leaving a profile site that they dug on the slope. Widespread very large natural avalanches continue to be observed throughout the area, and likely occurred on the 28th and 29th.

Snowpack information is limited outside of the Highway 20 corridor and Harts Pass. Let us know what you find if you get out into the backcountry!

Régions couvertes