Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Very large avalanches are possible in the Wenatchee Mountains where a thick recent slab overlays weak snow near the ground.  Avoid slopes 35 degrees and steeper above treeline, especially where you find strong over weak layering or signs of instability such as whumphing collapses. Freshly formed wind slabs are possible near and above treeline, and these could step down deeper weak layers in the Wenatchees. 

Problemi valanghivi

  • Persistent Slabs

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

    You can trigger very large and destructive avalanches in the Wenatchee Mountains and anywhere with less than 5 feet of snow on the ground. Persistent slab avalanches can break widely across terrain features and are very surprising. Stay off of, and out from underneath large slopes 35 degrees and steeper near and above treeline. Make sure to stop and re-group in areas well away from avalanche terrain, as you could trigger one from a distance. Consider avoiding avalanche terrain altogether in the Wenatchee Mountains, especially with freshly wind drifted snow or if you find signs of cracking or whumphing. 

    Up to 3 feet of recent snow fell ending on the 6th. In the Wenatchee Mountains, you can find this resting on weak, old layers of snow. The weak snow will look loose, sugar-like, and granular. You may find old crusts near the weak snow as well. Persistent Slab avalanches are most prevalent in the Wenatchee Mountains and the far eastern edge of the Cascades. Closer to the Cascade crest, it's less likely that you'll trigger these dangerous avalanches, though not impossible. Near the Teanaway, Salmon la Sac, Icicle, Lake Wenatchee, Upper Entiat, and Holden Village areas you may find a stronger, deeper snowpack. 

    (1/6/2021) Explosive triggered hard slab avalanche at Mission Ridge, NE, 6300ft. Photo Jake Larson

  • Wind Slabs

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

    Easterly winds have created fresh, shallow slabs near and above treeline in exposed locations. Look for snow surface texture that indicates recent slab development, such as rippled and wavy surfaces. Check for signs that you could trigger an avalanche such as shooting cracks and feeling for punchy, or hollow sounding drifts. Steer around the edge of cross loaded gullies, unsupported roll-overs, and other drifted features on steep slopes.  In the Wenatchee Mountains and areas on the eastern edge of the zone with a shallow snowpack, fresh windslabs have the potential to step down to deeper weak layers. 

    Cornices may be large from the long storm cycle last week. Give them a wide berth and make sure to keep your distance by staying off of, and out from underneath these overhead hazards.  

    Example shallow wind slab.

Avalanche Discussion

There's a notable variation in snowpack characteristics in the zone. A deep, strong snowpack exists near the Cascade crest. Further east the snowpack is more shallow, and may hold weak layers of old snow near the ground.

A skier triggered a D2 near Mission Ridge on Friday on a northeast aspect at 6,200ft. Mission Ridge Ski Patrol triggered a small slide with explosives that stepped down to weak snow near the ground. On Wednesday, they triggered very large avalanches with explosives on NE aspects around 6,300ft. Observers in the Wenatchee Mountains reported another crop of surface hoar on Saturday, and whumphing collapses above 5,600ft indicating you could still trigger a persistent slab near the ground. Observers below treeline in Naneum Meadows found great riding conditions and minimal signs of instability.

To the west, observers have found that snowpack concerns are more limited to new snow and wind concerns. On Saturday, observers above Eightmile Lake reported stong winds at ridgetop, and triggered a shallow windslab on a north facing slope at 7,200ft. Further up the Icicle Creek, and on Dirtyface others reported no signs of instability, and traveled comfortably on steeper slopes near and above treeline. Observers continue to report very large avalanches within the zone from the storm and avalanche cycle last week, such as a D3.5 off the southeast face of Dirtyface above Lake Wenatchee. 

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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