Bulletin d’avalanche

West Slopes South

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 5 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

The storm will continue to produce snow for most of the West South on Monday. Ease into terrain slowly and look for red flag signs of instability such as shooting cracks or recent avalanches. You will be more likely to trigger an avalanche on convex slopes or in wind-loaded terrain over 35 degrees.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    Continued snowfall in the West South will maintain our concern for Storm Slabs on Monday. You may find that these slabs are thicker and possibly more reactive as you ascend in elevation or on the volcanoes. The most likely locations for you to trigger one of these avalanches are on convex or unsupported slopes over 35 degrees. Of course, areas where the snow was able to drift the snow into deeper piles near ridgelines or rocky features, such as gullies or the base of cliffs, will also have an increased likelihood of producing avalanches. You can look for heavy snow over lighter snow by using quick hand pits as you travel or feeling for density changes with your pole or foot. Shooting cracks or blocks or snow failing during upslope tests can give you an indication that the upper snowpack contains a slab. If these clues make you question stability, seek out small test slopes to see how the snow is reacting to your weight. If any of your tests point toward slab avalanches or you are in doubt, default to slopes under 35 degrees.

    (2/20/2022) Shooting cracks in a wind loaded area near the top of Hogback Mt. These cracks are 6-8 ft long and indicate that the upper snowpack has slab qualities. Photo: Dallas Glass

Avalanche Discussion

As of Sunday evening, this storm has produced around a foot of snow in most locations around the West South. In some areas closer to the crest, you may find just shy of a foot, while on the volcanoes you will find closer to 14”. The West South is not done yet, and showers should reinvigorate to produce a few more inches throughout the zone. On Sunday, NWAC forecasters at White Pass reported that the new snow was generally well bonded to the underlying crust (2/19), but failures were produced in hand shears and small column tests near this interface. Crystal Mountain Pro Patrol also reported a favorable bond and triggered small slabs on mid-elevation slopes during their mitigation efforts this morning. Some sun breaks helped to consolidate and “slab up” the snow mid-day.

On Monday, you need to continue to check all of the snow down to the Valentine’s Day Crust to see how the bonding and slab qualities are progressing before stepping into consequential terrain. It could vary greatly depending on aspect or elevation due to the variable surfaces observed prior to this storm or exposure to sunshine. Despite the return of snow, we are inching ever closer toward spring where the sun is stronger and the weather can be more erratic. Sun breaks on Monday could again help the snow to consolidate or even trigger some rollerballs and loose avalanches on steep sunny slopes. Be sure you are watching how the weather is changing the snow throughout the day and be prepared to alter your plans.

Régions couvertes