Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

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

In sintesi

UPDATE: Increased avalanche danger at upper elevations to reflect greater than anticipated morning snow totals. Triggering a large avalanche will be more likely at mid and upper elevations. 

New and reactive wind slabs may form on the lee sides of exposed features at any elevation. Use visual clues such as sharp cornices and smooth pillow-like drifts to identify and avoid steep wind loaded areas.

Problemi valanghivi

  • Wind Slabs

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

    New wind slabs may form on the lee sides of any exposed feature Tuesday night during a very strong wind event. Due to the direction and consistent nature of the winds in this storm, you should find the majority of slabs on SW-N-NE aspects. Very strong winds, particularly near the crest, may create a more erratic loading pattern and scour ridgelines. In some locations, these new slabs could develop over weak snow grains buried Saturday night. As a result, avalanches may trigger easily, propagate widely, and run quickly. With the potential for very touch slabs on some unusual aspects, this is a great time to approach these potentially unique wind slabs with caution. Use visual clues such as fresh cornices and smooth drifts to identity wind loaded features. When you suspect wind loaded snow, go around and choose lower angled, less wind affected, or more treed slopes to avoid the wind slab problem.

    (1/23/2021) Small and shallow wind pockets were found to be reactive, producing long shooting cracks in the Crystal backcountry on 1/23. This isolated slab failed on weak facets.

Avalanche Discussion

While areas closest to the Cascade Crest should see the brunt of the strong winds, locations near the volcanoes will likely receive more snow. As a result, wind slabs of varying thickness, firmness, and reactivity may occur depending on your location in the West South zone. This small storm will add a few inches of low-density snow to precipitation events since January 13th that continue to grow the upper snowpack. Hiding within the recent snow may be weak snow grains. Sugary facets, feathery surface hoar, and a thin sun crust were all observed and potentially buried on Saturday (1/23). If this very weak and challenging interface exists, avalanches may remain possible much longer than normal. So far we have not seen avalanches on these layers because no slab existed, but as snow continues and the wind blows that may change. 

The recent snow sits above a very prominent and often icy (1/13) crust. Away of wind-affected areas, expect very unconsolidated and poorly bonded snow. As a result, you may trigger small loose/sluff avalanches. Even small slides can harm you if they knock you over a cliff or into an open creek. 

While travel conditions continue to improve with the recent snow, variable and sometimes icy surfaces still remain. Expect firm slopes in forested areas and along wind-scoured ridges. 

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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