Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Expect a dynamic day with increasing danger while the snowfall accumulates. New snow avalanche problems should be highest on your radar, with loose dry, storm slab, and wind slab all becoming possible and could run on a slick crust. Avalanches may become easy to trigger, especially at upper elevations, and once about 5" of snow has fallen. 

Problemi valanghivi

  • Wind Slabs

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

    As the new snow falls and begins to accumulate, you could trigger shallow, fresh slides on steep slopes. Avalanches could take many forms on Wednesday; Loose dry slides, storm slabs, and wind slabs. Wind slabs are the problem advertised here, because these could be larger and wider than the other ones. You may be able to trigger these near ridges, the base of cliffs/rocks, or convex rolls in terrain. Older wind slabs exist beneath the new snow, may not be completely bonded to the slick crust below, and could add to the avalanche size. Look for deeper drifts, cornices, and textured snow surfaces to identify likely wind slab locations. You can also use your probe or pole to feel for stiffer layers over softer layers. Steer around these wind slabs in steep terrain. 

    Look for signs of instability like small sluffs on steep test slopes, shallow slabs, and shooting cracks. Use these as a sign to keep your slope angles down. If you find more than 10" of snow has fallen, then expect larger slides and more dangerous conditions.

    Example small wind slab.

    Photo: Public Observation

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1.5–2.5

    A layer of buried surface hoar became problematic around January 8, and we continued to see avalanches on it for a few days. Now this layer is capped under a thin crust, but theres a slim chance that you could still trigger it with a heavy trigger, such as a snow machine or a few people standing close together.  The most suspect terrain is steep, planer slopes above 6,000ft and is relatively sheltered, with sparse tree cover. Steep and unsupported slopes could also be the places you might trigger a surprising slab on this layer.

    (1/7/2023)

    An example of what buried surface hoar looks like within the snowpack.

Avalanche Discussion

A few inches of new snow may help improve riding conditions on Wednesday. Theres a chance that the Wenatchee Mountains pick up a bit more snow than areas near the crest during the day with the southeasterly flow.  An observer reported finding fresh surface hoar on southerly aspects at 6,000ft near Blewett Pass on Tuesday. 

On Monday, there was a skier triggered slide at Mission Ridge below the Microwave Tower. The skier took a ride and was partially buried, though luckily did not report major injuries. They did, however lose their skis. A few other parties saw the avalanche or aftermath, and assembled a probe line and found the missing skis. Another observer reported finding shooting cracks and breaking out a small wind slab at 6,700ft on a NE aspect nearby. The low elevation snowpack is refreezing and becoming more supportable, but you could still expect slick and slippery crust on steep slopes at all but the highest elevations.

A subsantial warm and wet storm from Thursday through the weekend resulted in a widespread natural avalanche cycle with at least a few D3 wet avalanches, dozens of large wet avalanches, and many smaller storm/wind slabs. Prior to this last storm, there were many reports of folks triggering avalanches on an older layer of buried surface hoar and subtle crusts. These persistent weak layers may still exist above about 6,000ft.

Regioni coperte