Bulletin d’avalanche

West Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
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

Continued snowfall and gusty winds are sustaining slab avalanche danger in most alpine areas. Avoid steep slopes, especially if you suspect wind has drifted additional snow onto the terrain ahead of you. Reduce uncertainty and risk by sticking to lower angle, sheltered terrain.

 On Saturday morning, December 11th, an avalanche fatality occurred in the Silver Basin area of Crystal Mountain Ski Resort. See the forecast discussion below for additional details.

Problèmes avalancheux

  • Wind Slabs

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

     

    You will find the bulk of the avalanche danger on Sunday in wind loaded terrain with stiffer, more reactive slabs. There is plenty of new snow available for transport and more is expected. Continued strong winds - occasionally pushing into lower elevation terrain - will build new slabs on leeward slopes and behind prominent terrain features, even as slightly older ones stabilize and gain strength.

    Large, steep, open slopes in the alpine are obvious terrain features to avoid, but also be on the lookout for unstable slabs in less intimidating terrain. Convex rolls, gully walls, or around rocky outcrops are all places where you will be more likely to trigger an avalanche, possibly even in some below treeline areas.

    The best way to reduce your risk will be to simply avoid areas that harbor wind slab. Identifying these areas may be difficult as new snow obscures obvious signs of wind loading.

    Example of small,  snowmobile triggered wind slab avalanche. Evidence of wind transport is visible in the surrounding terrain.  February 2020.

Avalanche Discussion

On Saturday morning, December 11, a party of six backcountry tourers were traveling uphill in a closed section of the Crystal Mountain Ski Area known as Silver Basin. The party triggered a large avalanche on an N to E facing slope at approximately 6500’. While all members of the party were initially caught, four were partially or fully buried. A nearby party of two witnessed the event and immediately assisted in the rescue. Crystal Mountain Ski Patrol was also notified and responded to the scene. Unfortunately, one of the fully buried victims did not survive. NWAC and Crystal Mountain Ski Patrol will collaborate to conduct an investigation. Our deepest condolences to the family, friends, and community.

A much needed storm laid down significant new snow in the West Central zone with some below treeline areas seeing the first significant snow of the season. There are no recent observations from the West Central zone since the start of the most recent snowfall.  Observers in the adjacent West North zone noted strong winds occasionally drifting snow in some normally sheltered terrain around Heather Meadows on Saturday. Test slopes and other informal testing indicated reactive wind slabs.

A few more brief but intense periods of snowfall are expected in the North Cascades through Monday morning. This will keep stocked the supply of light density snow available for wind transport.

Early season hazards exist in many areas even with the fresh coat of snow. In some cases, they may pose more of a hazard as once visible stumps, boulders, creeks, etc. are now just hidden below the surface. In addition, shallowly buried objects will increase the consequences of being caught in an avalanche. You could easily get injured by being pushed into rocky terrain or trees.

Uphill travel reminder: Check in with your local ski area this weekend regarding terrain access and parking updates. Closed ski areas often share a similar snowpack and avalanche hazard as the surrounding backcountry. You may also encounter other hazards like active avalanche mitigation, unmarked obstacles, snowmobiles, groomers, and other heavy equipment as ski areas prepare to open. Be prepared to make your own assessments and handle emergency situations."

Régions couvertes