Bulletin d’avalanche

East Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

The sustained warm temperatures will prolong dangerous avalanche conditions. These large and destructive wet avalanches are very difficult to predict. The only way to manage this problem is to stay out of their way. Avoid traveling on steep terrain and be knowledgeable of the terrain above you, as natural wet avalanches may travel down through terrain further than expected.

Problèmes avalancheux

  • Wet Slabs

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

    Sustained warm temperatures with only superficial surface freeze overnight will continue to produce meltwater that drains through the snowpack and makes wet slab avalanches more likely. Recent snow from late February overlays a weak snowpack structure, creating the perfect setup for large wet slabs. Wet slab avalanches could break widely across large terrain features on weak layers 2-3 feet below the surface, and you may trigger them from low-angle slopes connected to steep terrain. Avalanches will be most likely midday through late afternoon.Avoidance is the only reliable strategy to manage this unpredictable problem. Stay out of harm's way by avoiding travel on and under all large slopes greater than 30 degrees, especially during the heat of the day. Lower elevations may see avalanches run from above, so know what terrain is above you and avoid lingering under large slopes or near steep drainages that can channel sliding snow from above. 

    Loose wet avalanches may be more widespread and predictable but could gouge deeply and become large and dangerous as they move down through terrain. The heat and sunshine will also weaken cornices. Give these overhanging chunks some space. They could trigger wet loose or slab avalanches.

    (1/29/2024)

    An example of a very large wet slab avalanche (d3) from late January.Mission Ridge Ski Area WS-ASu-D3-R4-O/G

Avalanche Discussion

The hot, sunny weather will continue on Monday, with freezing levels over 10,000ft yet again. We're still in the midst of this season's first big, spring-like warming event. Even though it is only March, this is a spring shed style event, and unusual avalanches are likely. A close call on Saturday, where snowmobilers triggered a very large avalanche in Ahtanum (East South) that failed on deeply buried weak layers, is an indication of the potential for these types of avalanches as we continue to warm the snowpack. With extended warm periods and a weak snowpack, it is very challenging to pinpoint when avalanche activity will peak. But we know avalanche conditions are dangerous, and we expect wet avalanches to occur naturally and be easy to trigger. Smaller wet avalanches, cornice falls, or snow shedding from cliffs can also trigger widely propagating avalanches on persistent weak layers. 

These long periods of uncertainty and unstable snow take conservative terrain management and diligent patience. Stepping into steep terrain at mid and upper elevations is simply just a game of chance; you may get away with it, or you could trigger a very large avalanche that is likely to injure or kill you. The weak snowpack structure is especially apparent in the eastern Cascades, where the snowpack is generally more shallow than at the crest. If you're venturing into these eastern zones, be prepared to step back in your typical terrain selection and understanding of the snowpack.

Your avalanche, snowpack, or weather observations are extremely valuable to the avalanche community. Help create a more accurate avalanche forecast by submitting your observations here. 

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