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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Points saillants

It'll be another day to let the snowpack adjust before trusting steeper slopes. The mountains have just begun to shed their winter coats, and more wet loose avalanches could be triggered from steep slopes with saturated or punchy snow. The thaw may increase the chances of large cornice fall, so watch out above. 

Problèmes avalancheux

  • Loose Wet

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

    Another warm day is in store, and with warm overnight temperatures, wet snow may continue to slide downhill on Wednesday. Wet loose avalanches may become more active as the day warms up. Signs of wet loose avalanche activity are rollerballs, and fresh fan-shaped avalanches with chunky looking debris. Slides may occur on all aspects and elevations. 

    There is uncertainty as to how the snowpack is adjusting, so keep an eye and ear out for signs of current activity. In any case, you could probably still trigger them on steep slopes, however. Loose wet slides could run far in very steep locations, and they could pull out wider slabs in some cases.

    (3/22/2022)

    Large (D1.5) wet loose avalanche in one of the main Cutthroat paths above Hwy 20.

    Photo: Andy Harrington

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    2

    Cornices are large, and may begin to sag and fail with the continued thaw. Any large cornice falls could be dangerous in their own right, and they could also trigger deeper avalanches below. Attempt to minimize your time underneath the honkers, and don't be afraid to steer widely around potential runout zones.

    Some shaded, northerly aspects near and above treeline may still harbor more deeply buried faceted layers. Large triggers, such as cornices could initiate deeper slab avalanches on these layers.

    Cornices may fail, and they could trigger deeper slabs below. March 10 photo of McGregor Mtn, NNE, 7,200ft on March 10.

    Photo: Matt Primomo

Avalanche Discussion

The warmup is on, and the snowpack has been shedding, trying to adjust. Observers reported seeing, and hearing numerous small to medium-sized wet loose avalanches on Tuesday near Washington Pass. Temperatures hit 43 degrees on Washington and Harts Passes on Tuesday afternoon. Sunday and Monday, observers reported triggering a handful small windslabs in higher, alpine terrain. The storm of the 14-15th delivered over 1-2 feet and brought an active day of natural and triggered avalanches. On wind-sheltered NW-NE aspects near and above treeline, observers found near-surface facets 1-2 feet below the surface and often on a crust. This layer (buried on March 8th in other zones) was the source of persistent slab avalanches near the Mount Baker ski area and other parts of the Cascades.

A deeper persistent weak layer still exists in the zone. The layer can still be found about 3 feet deep, sandwiched between eroding crusts on NW-NE aspects near and above treeline, and has been particularly problematic in the Harts Pass area. The most recent of these was triggered on March 9th in Allen Basin. While triggering an avalanche on this layer (the late January facets) is unlikely, the consequences could be serious. You can limit your exposure to shallow, rocky areas, and very steep and unsupported slopes. After a widespread avalanche cycle on 2/28-3/1, observers reported a number of deep crowns and avalanches throughout the zone that likely ran on the weak layer. See the avalanche occurrence database for more details.

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