Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Snow and moderate winds will bring increasing avalanche danger during the day on Tuesday. You may be able to trigger avalanches in wind drifted snow near ridges at upper elevations. Consider using low-angle approaches to ridgelines in wind-affected terrain. 

Problemi valanghivi

  • Wind Slabs

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

    On Tuesday, the central Cascades are getting a refresh of snow from a mild storm impacting the region. While this storm won't be a great snow producer, an upslope component on the East slopes could favor Mission Ridge and the Wenatchee Mountains. Most of the zone can expect 4-8 inches of snow accumulation, while Mission Ridge may end up with close to 10 inches. Moderate winds associated with this storm will easily redistribute the new snow onto lee aspects of ridgelines, potentially building sensitive wind slabs.   If you are traveling in open terrain at upper elevations, use visual clues such as textured surfaces and actively blowing snow to identify wind-affected terrain. If you see signs of instability, such as shooting cracks or collapsing, consider traveling on low-angle routes. Observers throughout the zone have found weak faceted snow on sheltered northern aspects. Wind slabs that form over these surfaces may be especially prone to triggering and break wider than expected. It will be worth a quick dig down to the old snow surface to investigate the interface before committing to steep slopes.

    (2/1/2022)

    Example of a shooting crack on a wind-loaded terrain

    Photo: Ryan Minton

Avalanche Discussion

Tuesday should start out reasonably quiet, with precipitation intensity picking up throughout the day. With the expectation of wind-loaded areas, precipitation amounts won't be enough to build large slabs. But as new snow depths increase, you may trigger mini storm slabs and dry loose avalanches in very steep terrain. Remember that terrain traps such as cliffs, rocks, trees, and open creeks can increase the consequences of even small avalanches. Observations throughout the zone have identified various surfaces such as slick crusts, weak snow, and even some dry snow that survived the rain at upper elevations. New snow may not bond well with these slick and weak snow surfaces, and persistent weak layers may get preserved, becoming a problem with future snow accumulations. We are still tracking older persistent weak layers, and observers at Holden found variable test results on weaker snow beneath a thin crust from Valentine's Day about 3ft down on a NE aspect at 5,600ft.Challenging travel will likely remain a significant hazard with thin snow cover at lower elevations and icy crusts creating the potential for long uncontrollable slides on steep terrain. In addition, a widespread avalanche cycle occurred throughout the Cascades on the 28th, and there are plenty of large piles of debris to navigate. 

 

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