Bulletin d’avalanche

East Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Mon
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

On Sunday, more light snow will add to this week's significant storm totals. You can trigger avalanches in the recent snow on slopes steeper than 35 degrees, especially where the wind has formed deep drifts. Minimize the risk of getting caught in an avalanche by sticking to lower-angle, wind-sheltered terrain and avoiding steep roll-overs and slopes above rocks or cliffs. 

Problèmes avalancheux

  • Storm Slabs

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

    You can trigger avalanches in the recent snow on a variety of steep slopes. The most dangerous areas will be at upper elevations and on leeward sides of ridges and wind-exposed features, where avalanches will be easier to trigger and big enough to bury you. In wind-sheltered terrain, you may be able to trigger slab avalanches or these slides may be of the loose variety. Consider the potential for avalanches on deeper weak layers. You can identify them by digging in the top 3 feet of the snowpack and using snowpack tests with planar, sudden failures.

    Stick to well-supported, lower-angle slopes and wind-sheltered terrain. Steer around typical trigger points like convexities, and unsupported features. Watch for recent avalanches, collapses, and cracks shooting through the snow to indicate the danger. Use small features and quick tests to see how easily the snow slides before traveling on bigger slopes.

    (12/26/2024)

    Skiers triggered a small avalanche on a convex feature. Delancey Ridge, SE, 5,200ft

    Photo: Forest McBrian

Avalanche Discussion

It's been a stormy holiday week. Sunday will bring calmer weather with only light snow. Saturday's windy storm delivered at least a foot of snow to many mountains in the zone and drifted slabs at upper elevations.  The 26th brought 10-12" of snow that fell with strong winds. A couple of smaller storms on the 21-24th delivered a total of 1" of water equivalent. Terrain below 4,000ft has seen some warming and light rain this week.

With all the recent snow, observers are still tallying the effect. Mostly, recent avalanches and signs of instability have been limited to recent storm interfaces. However, on Saturday a couple of observations of deeper instabilities stood out: A skier triggered an avalanche near Cutthroat Lake on a southerly, unsupported slope at upper elevations, not far from the ridgetop. This slide broke ~70cm deep in an older layer. On Delancey Ridge, an observer reported signs of instability at lower to middle elevations on a southeast aspect. They reported a collapse at 4,800ft, and then sudden results in multiple compression tests ~70cm below the surface on a prominent crust at 5,300-5,680ft. The height of snow there was 168cm.

On Thursday, observers on Delancey Ridge triggered small avalanches in the new snow and cracking on wind-sheltered slopes. At 5,500ft they found over 5 feet of snow on the ground and the Solstice crust is 1.5 feet below the surface. Observations from upper elevations and near the Cascade crest have been more limited than usual this week. The snowpack near the crest is over 7 feet deep. 

While recent temperatures have been warm, there's decent coverage at lower elevations and in the eastern mountains. On Thursday and Friday, observers in the Twisp River drainage found a relatively strong snowpack, though still shallower than at the Cascade crest. There was 70-100cm of snow on the ground near 3,000ft and depths increased with elevation. The wind transported a considerable amount of snow on Thursday. On Friday, observers didn't find wind slab instabilities below 6,500ft, but they may've existed higher in the terrain. 

In the foothills and eastern portion of the zone, you may find more weak layers than at the Cascade crest. Pay attention to red flag signs of instability, such as whumping collapses, and consider digging down to identify potential weak layers. The Loup Loup area has a relatively robust snowpack compared to many years, though still shallow compared to further west. An example of this is highlighted by last week's observations of small avalanches failing on a layer of buried surface hoar near Black Pine Lake. The surface hoar is likely less pertinent now that lower elevations have formed overlying crusts.

You can contribute to the avalanche forecast. Please let us know what you see in the mountains by submitting an observation. 

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