Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

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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 may still be able to trigger avalanches near and above treeline where the wind has drifted stiff slabs of snow. You may be able to trigger small loose avalanches on steep, wind-sheltered slopes where snow surfaces are soft and loose. Expect more dangerous avalanche conditions in the mountains near and east of Mazama.

Problemi valanghivi

  • Loose Dry

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

    Many snow surfaces remain soft and loose. You may be able to trigger loose, point release avalanches on steep slopes, well over 35 degrees. Use caution near terrain traps, like cliffs, gullies, and rocks where even a small avalanche could injure or kill you. Lots of soft, deep snow still exists from last week's storm.  Deep snow immersion is also a concern that could be life-threatening. Be vigilant around tree wells and stay close to a partner while traveling through the trees. 

    (1/6/2021) Examples of point release avalanches on Lichtenberg Mtn near Stevens Pass. Photo: Dan Veenhuizen

  • Wind Slabs

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

    While wind slabs are getting harder to trigger, they are not yet impossible. You may be able to trigger large avalanches on leeward, wind-loaded slopes near and above treeline. Cornices, wind features, and firm wind-stiffened snow are all signs that the wind has drifted snow. Watch for signs that you could trigger an avalanche such as cracks shooting through the snow and other recent avalanches. Steer around convex roll-overs or thickly drifted features on slopes steeper than 35 degrees. Cornices have become large. Make sure to keep your distance by staying off of them and don't linger under them. 

    From the 1st to the 5th southwest winds blew strong enough to drift snow and form slabs. Easterly winds on Thursday night to Friday may have been strong enough to form thin slabs at the highest elevations. 

    (12/31/2020) An example of wind features on Delancey Ridge at 7000ft on Dec 26th. You may see similar wind features (foreground right) and drifting from more recent winds on Friday.

Avalanche Discussion

You can find a big difference in the snow and avalanche conditions as you move through the zone. Near Washington Pass and even as far east as Delancey Ridge, most of the snowpack is strong and avalanche concerns are limited to snow that has recently fallen and built the uppermost layers. However, in the eastern part of the zone, you may be able to trigger a dangerous persistent slab avalanche. An observer near Aspen Lake reported a triggered avalanche on older weak layers of snow underlying the recent storm snow, whumping collapses, and propagating test results. In areas like the Winthrop foothills, the Twisp River and Lost River drainages, and areas east of Mazama the snowpack may be shallow and weak. Here, you may encounter similar conditions to those in the Wenatchee Mountains, where we've issued a Special Avalanche Bulletin. If you're venturing into these eastern mountains, expect a weaker more dangerous snowpack, use extra caution near avalanche terrain, and be prepared to make your own snowpack assessments. 

On Thursday, observers in the Hairpin Valley reported developing surface hoar (6-8mm) resting on a crust. Keep monitoring this layer to see if it survives long enough to get buried. Also near the Hairpin on Washington pass, a widespread cycle of slab avalanches (up to size D2.5) likely occurred on the night of January 5th. A fracture line profile at one avalanche revealed that it ran 55cm below the surface. Just south of the zone border, an observer near Holden village reported fresh loose avalanches on Thursday along with slab avalanches (to size D3) from earlier this week. 

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