Bollettino valanghe

East Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Wind slabs formed rapidly on Saturday, and observers reported unstable conditions with long shooting cracks. Slabs may continue to be reactive on Sunday, and in some areas may step down to become deeper, larger avalanches. Use lower angle, more supported features as you gain elevation, especially if you find signs of instability like shooting cracks or hear whumphing. 

Problemi valanghivi

  • Wind Slabs

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

    Strong winds have been drifting recent snow into more cohesive slabs on exposed mid and upper-elevation slopes. These should continue to be reactive on Sunday, as they may rest over weaker snow, sometimes on a crust. Slabs could be 10"-20" deep in favored locations, and in some areas may have the potential to step down to deeper crust layers. Use caution as you gain elevation, and stick to lower angled slopes if you venture to the alpine. Look for signs of instability like shooting cracks, whumphing collapses, and observe for recent wind loading. Likely spots to initiate wind slabs are on open slopes exposed to the wind, near outcroppings, at the top of convex rollers, and steep, sparsely treed slopes. 

    Textured surfaces, deeper drifts, and cornice formations can also help you identify likely wind slab locations. Feel for stiffer snow as you travel. Outside of wind affected areas, small loose dry sluffs could run fast. If you find the snow is prone to sluffing, or cracking, than its recommended to steer around steep, consequential slopes. 

    Example of textured, wind loaded area.

    Photo: Hans Brubaker

Avalanche Discussion

Observers reported strong winds moving quite a bit of snow on Saturday. The winds have been impressive for the zone, and may have done a number on snow surfaces. Multiple observers reported turning around due to obvious shooting cracks and heavy wind drifting on Saturday east of Washington Pass. We know slabs are out there, though uncertainty exists with how reactive they may continue to be.

An observer on Thursday found 3" of new snow near Blue Lake. He reported light drifting snow during the day, while winds were just beginning to increase. Earlier in the week, observers in the Kangaroo ridge area reported firm, wind affected surfaces at very high elevations with minor cracking. Prior to Friday, observers found nice powder riding conditions and a barely noticeable crust below recent snow accumulations. 

The top foot or two of the snowpack holds multiple crusts at mid elevations, and one more stout crust exists from early December to about 8,000ft. These crust layers have been found with and without weaker snow around them. As more snow accumulates, these will be worth digging down and testing. Region wide, these crusts are expected to become main players for avalanches through the weekend and into the week. For an idea of what you might find in the southern portion of this zone, like mid-Twisp River drainage, check out these observations from the Holden area.

You can help out by contributing to the forecast. Submit an observation, and let us know what you see! 

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