Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Heightened avalanche danger exists at upper elevations where you can trigger avalanches in recently drifted snow. At these same elevations, it may still be possible to trigger a very large and deadly avalanche on isolated slopes. The best way to deal with the uncertainty of triggering avalanches on deeply buried weak layers is to stick to slopes less than 35 degrees.

Problemi valanghivi

  • Persistent Slabs

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

    Persistent slab avalanches could be very large and could bury or kill you. These dangerous and surprising avalanches can catch even the most experienced backcountry travelers. While it is getting harder to trigger persistent slabs, it's not yet impossible. With uncertainty about how easily you can trigger these avalanches, it's important to give them some time to heal. The best way to stay safe is to avoid where these avalanches exist. Keep your distance from slopes 35 degrees and steeper that are open enough and tall enough to produce large avalanches. Watch for obvious signs of instability like recent avalanches, whumphing collapses, or cracks shooting through the snow.

    Persistent slabs are more likely closer to the Cascade crest, in the western and northern portions of the zone. If you'll be traveling there, check out the neighboring Steven's Pass and East North zones. The most dangerous slopes will be at the highest elevations, where snow stayed mostly dry and where southwest to west wind drifted snow over the past few days. You can find a thin weak layer of small facets (and in places surface hoar) above a crust buried about 1.5-3 feet below the surface. Further east, and in the Wenatchee mountains, there's less snow. There you may not find enough cohesive slab to cause a problem.

    (12/22/2020) A very large slab avalanche (at least D2.5) in Big Slide creek on an ESE aspect at about 7,300ft, near the Icicle drainage. This avalanche likely occurred Dec 19-20th.

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1

    Watch for triggering avalanches in recently drifted snow. Following travel advice for the Persistent Slab avalanches will keep you from triggering avalanches in the storm snow as well. Avoid leeward slopes where the snow looks thick and pillowed. Watch for wind features in the snow and areas of deeper snow adjacent to shallower areas. Feel for stiffer snow under your skis or feet as signs of drifting. Avalanches will be largest and most dangerous at the highest elevations. You may also be able to trigger small wet avalanches on lower elevation slopes as the day warms.

    (12/22/2020) Avalanche workers intentionally triggered a fresh wind slab avalanche on an ENE aspect at 5,000ft near Stevens Pass. The crown was 200ft wide and 18-24" deep.

Avalanche Discussion

We've issued a Special Avalanche Bulletin for the neighboring East North zone. With sunny skies on Thursday, you may see a few small loose avalanches on steep southerly slopes.

We believe a widespread cycle of large to very large natural avalanches occurred over the weekend. These avalanches likely involved a crust and weak layer buried in early December. An observer reported a very large slab avalanche (at least D2.5) in Big Slide creek on an ESE aspect at about 7,300ft, near the Icicle drainage. This avalanche likely occurred Dec 19-20th. While observations have been limited, we've received good confirmation from neighboring zones to the north and west. In adjacent zones, a prolonged cycle of widespread avalanches occurred from the 18-21st. There is a lot of variability in snowpack depth just east of the crest where you may find 6ft of snow at 6000ft, but east of Highway 97 in the Wenatchee mountains you may only find a few feet at the same elevation.  

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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