Bulletin d’avalanche

East Slopes North

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

You may not get many warnings as we're a number of days post-storm, and obvious signs of instability are waning, but large, wide, and surprising avalanches remain possible in some areas. Winds have transported snow into slabs on a variety of slopes, so besides persistent slabs you could trigger smaller, shallow wind slabs. Expect another very cold day, so bundle up and bring extra gear to keep a potentially bad situation from becoming worse. 

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–2.5

    Dangerous persistent slab avalanches are possible in the eastern mountains. These avalanches can be surprising, and they can break widely across terrain features. You can trigger them from below or from long distances away. We recommend putting a large buffer of terrain between you and large open slopes 35 degrees and steeper. Only expose a person at a time to avalanche terrain. Stop and regroup in safer areas, well away from and out from under any steep slopes. Watch for obvious signs of danger like shooting cracks or whumphing collapses, though these signs are tapering off as get further out from last weeks storm.

    A weak crust/facet combination 2-3 feet below the surface. The further east you are from Washington Pass and the Cascade crest, the weaker and shallower the snowpack will be. Observers have reported whumphing collapses and other signs of these avalanches on Delancey Ridge. On the 9th, a number of natural avalanches likely ran on old weak layers near Cutthroat Lake (see photo). We believe those locations make up the western boundary of this problem. 

    (1/12/2024)

    Natural avalanches on Tamarack Peak, near Harts Pass. These likely occurred Jan 11th with northwest winds. We don't know exactly which layer these avalanches ran on, but they look suspiciously like persistent slab avalanches. E-SE, 7200ft

    Photo: NCH

  • Wind Slabs

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

    Winds have drifted the very low density snow into shallow slabs on many slopes. Strong winds from many directions have built slabs on a variety of aspects. Some slabs may be hidden or obscured. Feel for wind-stiffened snow as you travel, and use visual clues as well as you can to identify wind-loaded or recently wind-loaded terrain features. Avoid steep slopes where you expect to find these stiff, wind-drifted slabs, especially if finding signs of instability like shooting cracks or hear whumphing collapses. Any small slab near the surface could step down and become a much deeper, wider, and potentially unsurvivable slide. 

    (1/7/2024)

    Even with little new snow, a natural wind slab occurred between 1/6-1/7 near Harts Pass.

    Photo: Jason Davis

Avalanche Discussion

Temperatures hit -28 at the lower Washington Pass site on Saturday, wow thats cold! Winds were light at the station, but may have been strong enough to continue drifting snow around. In past day, observers have reported wind-affected surfaces, even in some low-elevation terrain. Recent storm totals are about 2 feet since the 8th. On the 11th, observers on Delancey Ridge and near Cutthroat Lake triggered small avalanches in recent storm snow and fresh drifts. Late in the day and overnight, natural avalanches ran due to northwest winds. Near Harts Pass, some of these may have run in older weak layers. On the 10th, observers reported a number of large, natural avalanches over 2 feet deep near Cutthroat Lake (NE, ~6,800ft) that may have run on a crust from December 30th. On the same day, observers on Delancey Ridge reported over 20 rolling collapses at all elevations on a similar crust/weak layer that developed during the prolonged dry periods in December. 

"Weak and variable" continues to sums up the snowpack. You may find up to 6 feet of snow on the ground at upper elevations near Washington Pass, with half that much in the mountains near Mazama. On the 12th, NWAC observers found a shallow, weak snowpack near Banker Pass and Goat Peak. There are several decomposing crusts and layers of sugary facets that developed throughout December. In some locations, these layers present as individual layers; in others, they all meld together. Near and west of the Cascade crest the snowpack is deeper, has less weak layers, and the crusts are typically thicker and more stout.

If you're in the mountains, let us know what you see. Submit an observation here!

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