Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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

Warming temperatures and sun will raise concern for falling cornices. You may be able to trigger loose avalanches on very steep northerly slopes. 

Problemi valanghivi

  • Cornices

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

     Cornices top many ridgelines and steep features above treeline and have been occasionally falling.  Avoid lingering on or under large cornices. They could easily be big enough to injure you. If you're traveling on a ridge, check that you're standing above part of the mountain and not on unsupported snow. Clues like exposed rocks and vegetation can tell you where you can travel without being on an overhung cornice. Give cornices a wide margin as they can break further back onto the ridge than you may expect.

    Thursday's warm temperatures and clear skies could be enough to make cornices drop from where they're overhung and unsupported. Observers have reported ongoing cornice fall in the Washington Pass area in the past 10 days. I watched one fall in Copper Creek on Monday. Some of these have resulted in avalanches that wouldn't have occurred otherwise.

    (3/8/2021) Large cornices sagging high above the Hairpin Valley.

Avalanche Discussion

A slow warming trend will continue this week. Shallow wind slabs built from west and southwest winds above treeline as recently as Monday. For Thursday, they'll be isolated and difficult to trigger. About 10" of soft dry snow can be found on most sheltered northerly slopes. You may be able to trigger dry point releases on slopes steeper than 40 degrees. Use caution around terrain traps such as gullies and cliffs where these small avalanches could hold some consequences. While crust and previous warming on solar aspects limit our concern for wet avalanches, it's worth keeping them on your mind.

On Monday, I checked out multiple a variety of slopes at Washington Pass in the Hairpin Valley and beyond. We triggered small loose dry avalanches, a very small wind slab, and watched a natural cornice fall. You may find some of the same conditions on Thrusday. The snowpack is generally strong, deep, and without any layers of concern. In the top 2 feet of the snowpack, I did find a couple of interfaces with strong-over-weak layering. Investigating these interfaces revealed no signs of instability or reasons for concern at the time.  A widespread avalanche cycle occurred in the zone around February 22nd and many crowns and debris piles are still visible. Further east, the snowpack is more shallow and could potentially harbor persistent weak layers.

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