Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Even with all the new snow, the greatest danger remains localized to areas where the wind drifts the snow into firmer and deeper slabs. As the storm continues, these avalanches could become larger and more widespread, especially at upper elevations. Look for clues like fresh cornices and blowing snow to figure out which slopes to avoid. 

Problemi valanghivi

  • Wind Slabs

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

    Even with all the new snow, it’s the areas where the wind developed firmer and thicker slabs that pose a very real danger. Strong winds and continued snowfall should combine to grow wind slabs at mid and upper elevations. By Thursday many of these potential avalanches could be more than a foot thick and large enough to kill you. This avalanche problem isn’t one to go poke at and try to test. Instead, use visual clues like blowing snow, sharp cornices, and textured surfaces to figure out which slopes hold wind slabs and avoid them. If you suspect the wind loaded a slope, steer around it, and find lower angled or less wind-affected terrain.

    (12/22/2021)

    This small wind slab was intentionally triggered on a test slope Wednesday. As these slabs grow thicker they will become more dangerous.  SS-ASc-Dr-D1-I 

    Photo: Mt Rainier Rangers

  • Storm Slabs

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

    Cooling temperatures, light snowfall rates, and a good bond to the old snow surface should all help limit the potential for storm slab development. However, as the snow continues to pile up, at some point the storm totals become concerning. While we don’t expect a widespread storm slab issue, don’t be surprised if you trigger a small slab in wind-sheltered areas. This is most likely to occur in very steep terrain, on convex rollovers, or in locations close to the volcanoes where more snow should fall. If you see more than an inch of snow accumulate each hour for several hours in a row, anticipate more widespread storm slabs. You can always use your hand to dig into the snow and look for strong over weak slabs and blocks that fail easily. When in doubt, seek out slopes less than 35 degrees.

    (12/22/2021)

    You can dig with your hand to look at the new storm snow and search for strong over weak slabs. 

    Photo: Andy Harrington

Avalanche Discussion

Several key factors continue to work in our favor during this storm and limit the size and scope of the avalanche danger. Snow surfaces warmed significantly on Tuesday, and we even saw some natural wet avalanches. Since then temperatures have slowly cooled allowing the new snow to bond well to the old surface in most locations. This cooling pattern should continue to help the new snow fall right-side-up. Similarly, the modest 24 hr snow totals and generally light snowfall rates continue to limit the creation of new slabs. On Wednesday snow totals around the West South zone ranged from 4 to 8”. We could see an additional 6 to 12” by Thursday afternoon. 

As the previously wet snow surface freezes it will form a new crust (12/22). Even though several layers still exist in the upper snowpack, this curst should limit any avalanche activity to the current storm snow.

Regioni coperte