Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

Dangerous conditions continue as significant snowfall and wind have added a heavy load and stressed older layers of weak snow.  Stay far away from and well out from under wind-loaded, open terrain 35 degrees and steeper. Consider avoiding avalanche terrain at upper elevations where you can trigger very large and destructive avalanches that could break widely across slopes.

Problemi valanghivi

  • Persistent Slabs

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

    The new snow and strong wind will increase the chances for triggering avalanches 3ft to 4ft deep. Persistent slabs can propagate widely across terrain features and can result in very large and deadly avalanches. Stay well out from under any large open slopes steeper than 30 degrees, as they can be triggered from a long distance away or from below. Be alert to signs of instability such as shooting cracks, and whumphing collapses.

    Recent observations continue to indicate that large slab avalanches can release on a crust from mid-January. These have occurred mainly on Northwest to Southeast aspects above 5,500ft. The Salmon la Sac, Icicle, and other areas on the southwestern edge of the zone could be favored for snowfall and could hold dangerous conditions on Sunday. While slabs are thinner and the danger may be less elevated in the Wenatchee Mountains, the avalanches will be similar. When the snowpack is this complex, keep your terrain choices simple. 

    (2/3/2021) This natural avalanche likely occurred overnight on 02/02. Similar to other slides in the East Central, it failed on facets above the 1/13 crust in non-skier compacted terrain of Crystal Mt. It occurred on a SE aspect at 6500'. Crown depth 2'. Photo: Crystal Mountain Ski Patrol

  • Wind Slabs

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

    Strong winds will continue to transport the snow in open and wind-exposed terrain. Feel for wind stiffened or hollow sounding snow as you enter open terrain, and change aspects.  Any avalanche in the new snow could step down to deeper weaker layers and result in a very large and deadly avalanche above 5,000ft. Consider the terrain you're connected to and avoid steep, open wind loaded slopes. Stay alert to indicators of wind slab such as heavy snow drifting, shooting cracks and whumphing collapses. Small soft slab avalanches are possible on steep, sheltered slopes where more than 8" of new snow falls.

    (2/1/2021) From White Pass on Monday: Example of a small wind slab avalanche stepping down to weaker deeper layers.

Avalanche Discussion

Light snow and westerly wind will continue through the region. Expect that overnight snow will favor areas closer to the crest such as the Salmon la Sac, and the storm will produce more wind than snow for the Wenatchee Mountains. 

On Sunday, observers on Blewett Pass found about 6 inches of new snow with lots of blowing snow forming drifts 1-3 feet deep.  The saw cracking in wind drifted snow and tests failing in the mid-January crust-facet layer. On Saturday observers reported a D2 natural avalanche near Van Epps Pass and a D3 sized avalanche that resulted in a burial with no injuries near the Easton Sno Park. Observers reported a natural D2 avalanche on an east aspect at 5,500ft west of Blewett Pass on Friday. This appeared to have run on the deeper crust from mid-January. On Thursday, a snowboarder took a ride with a wind slab at Mission Ridge on a Northwest aspect in the Near Treeline elevation band. Luckily they escaped unharmed. An observer reported a number of large (up to D2.5) avalanches with the recent storm from February 1 or 2 near Holden Village. On Wednesday, Mission Ridge Ski Patrol reported 4 large hard slab avalanches with control work. These likely ran on the crust from 1/13, and were roughly 24"+ deep x 100ft wide in ridgetop, or near ridgetop terrain. Whumphing collapses such as those reported by forecaster, Matt Primomo, near the summit of Mt Lillian on Tuesday indicate that deeper weak layers are primed to avalanche. In all parts of the zone, weak structure can be observed in the top 2-3 feet of the snowpack, and could result in an avalanche. These include facets resting on a crust from mid-January, or a sandwich of crusts from that same time. At lower elevations, you'll find less new snow and a stronger recent rain crust. 

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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