Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The snowpack is primed for human triggered slab and loose avalanches. At upper elevations, slabs could be large and deeper due to wind drifting. Recent storms are stressing deeper weak layers in areas with a shallow snowpack, such as the eastern edge of the zone. Look for signs of instability, and steer around steep open slopes, as well as unsupported terrain at mid-elevations.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2

    Over 20" of new snow has fallen in the past couple of days. Steer around steep slopes while the snowpack adjusts to this hefty new load. You could trigger a large slab avalanche within the recent storm layers. Slabs could be deeper and thickened by wind at mid and upper elevations. The new snow may be hiding recently buried wind slabs on a variety of aspects and in unusual locations. Look for signs of instability such as shooting cracks or whumphing collapses. Places such as steep, convex rollovers and unsupported slopes will be the easiest places to trigger a slab within the new snow. At mid-elevations and further east, storm slabs have the potential to step down to deeper weak layers.

    Loose dry avalanches may be easy to initiate on Tuesday. Look for these fan-shaped slides that start from a point (also known as point releases). In steep terrain, these could entrain lots of snow, and create large avalanches. 

     

    (1/2/2021) Storm slab in nearby East Central Zone.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Heads up, persistent slab avalanches may begin to react with this new load. A weak layer of sugary snow sits atop, or below a thin icy crust from early December. Keep this deeper layer at the top of your mind at mid elevations and further east where the snowpack is more shallow. In most areas near the crest, this layer has already undergone a substantial avalanche cycle, and may not be a problem anymore. As you travel, assess for signs of instability like recent avalanches, whumphing collapses, or cracks shooting. The next couple of days will be a good time to stay off of steep, open slopes as storms continue to stress these deep weak layers. The most dangerous slopes will be mid elevation, unsuspecting slopes in sparse trees, and large open starting zones in the eastern edge of the zone where the snowpack is shallow.

    (12/31/2020) Orange lines outline crowns and debris from a very large (+D2.5) slab avalanche that occurred during a widespread avalanche cycle on Dec 21st. The red line shows a small slab avalanche that occurred this week, as loose snow pouring off the cliffs triggered recently drifted slabs about a foot below the surface. NE, 6500-6700ft, West Fork of the Methow River. Photo Josh Hirshberg.

Avalanche Discussion

On Monday, observers reported trees collapsing under the weight of the heavy new snow up near Cutthroat Drainage. Others noted that the new snow had more body than it did on Sunday, a bit more slab structure. The storm produced significant accumulations for the mountains north and east of Winthrop, and may stress deeper weak layers there. Sunday, an observer reported an isolated whumph near a windloaded ridgeline at 6,800ft in the Cutthroat Drainage. A observer in the Twisp River found ongoing wind transport in the alpine throughout the day. Digging down on a SW aspect at 5,800ft, he got sudden collapse test results down 75cm on the Early December Crust. Other recent snowpack tests showed that propagation was possible on this interface about 2 ft down at around 5700' on Driveway Butte. 

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources. Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

Regioni coperte