Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
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

You can trigger avalanches in recently drifted snow on upper elevation slopes that are steeper than 35 degrees.  In the eastern mountains, recent collapses and snowpack tests suggest you may trigger avalanches in older weak layers.  Consider traveling in lower angle terrain until you can evaluate the snowpack in this area. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    You can trigger avalanches where you find fresh wind drifts and slabs of recent snow on leeward sides of ridges. Avalanches will be bigger and easier to trigger above treeline. Use caution on wind loaded slopes steeper than 35 degrees and steer around typical trigger points like convex rollovers, unsupported slopes.  As winds shift to the SW later Monday night, look for a change in recent loading patterns. 

    On Sunday, observers in the Cutthroat drainage got cracks and a small avalanche to break on a wind-loaded southeast slope between 6,000-6,300ft. These broke about 1-1.5 feet below the snow surface on an interface of recent snow and buried surface hoar. So far it seems a wind-drifted slab is needed for this interface to be problematic. It's worth monitoring it on sheltered slopes as it may become an issue as more snow accumulates.

    (1/31/2021) Cracks and a small chunk of a slab triggered in a drift on a leeward SE aspect near treeline just east of Washington Pass. Photo: Josh Hirshberg

Avalanche Discussion

On Monday, observers in the Twisp drainage experienced collapses at 4800'. Snowpack tests showed the potential for propagation 1.5 feet down on the Jan 24th weak snow (facets) layer at 5700'.  This ties into an observation in the eastern mountains from last Wednesday reporting cracking and collapsing on older facets in snow from early January.  To sum it up, we have higher uncertainty with a shallower, weaker and potentially more dangerous snowpack in the eastern part of the zone. If you travel to areas such as the Chelan-Sawtooth Mountains, Twisp River, and Chewuch drainages, take time to dig in the snow and look for older weak layers. Consider traveling in lower angle terrain and smaller terrain features.  We don't have any confirmed reports of persistent slab avalanches, but you'll need to evaluate the upper snowpack carefully before committing to more consequential terrain. 

Light snowfall has slowly loaded a variety of snow surfaces since January 24th. On Sunday in the Cutthroat drainage, professionals checked out a layer of small rounding facets over a crust that was buried on the 24th. On a southeast aspect around 5,700ft, they found the facets 54cm (about 2ft) below the surface.  Similar to the layer of buried surface hoar (see wind slab discussion above), it's a good idea to monitor these layers with tests as we continue to get snow. If we get enough of a load, these layers could produce large and dangerous avalanches. If the snow comes in gradually and doesn't overload it, these layer may become a non-issue. At upper elevations near and just east of Washington Pass, the mid and lower snowpack is deep and strong.

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.

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