Bulletin d’avalanche

Stevens Pass

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

Dangerous avalanche conditions will continue above treeline. You can trigger avalanches big enough to bury or kill you where the wind as drifted thick slabs of snow. There's now enough snow in wind-sheltered terrain below treeline to trigger avalanches.

Problèmes avalancheux

  • Wind Slabs

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

    Use caution on leeward slopes 35 degrees and steeper. Steer around areas where the wind forms thick drifts and pillows. Avalanches will be larger and easier to trigger above treeline. Watch for shifting wind direction and loading patterns at upper elevations. Winds had previously been out of the west and will switch to southeast on Monday. Use a probe or pole to feel for deeper drifts. Indicators of the danger are recent avalanches, cracks shooting through the snow, and wind transported snow.

    (12/11/2021) A crack in a wind drift. Cracks broke to interfaces ~20cm and ~40cm below the surface within storm snow layers. E, 5180ft, SPMR Photo: Josh Hirshberg

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1

    You may be able to trigger avalanches on slopes steeper than 35 degrees where you find hard over soft layering or interfaces that break easily within the top 2 feet of the snowpack. Other signs of instability are recent avalanches, cracks in the snow, and test slopes that slide easily. Quick snowpack tests can be useful to assess if the snow could slide before you commit to steeper terrain.

    (12/12/2021)

    At the crown of a small (D1) skier triggered avalanche. This ran in new snow that accumulated since 12/11. 5100ft, SE, Stevens Pass

    Photo: Craig Muderlak

Avalanche Discussion

The weekend was busy and active in the backcountry near Stevens Pass. On Sunday, observers reported triggering numerous small (D1) slab avalanches in steep terrain below treeline. These avalanches occurred on a range of aspects (NE, SE, S), were 1 foot deep or less, and the character and width were consistent with storm slab instabilities. On Saturday, both natural and human-triggered avalanches were reported with the bulk of these avalanches being small slab avalanches on leeward sides of ridges and wind-loaded slopes.

Since December 8th the Schmidt Haus weather station recorded over 50" of snow accumulation with about 4" of water equivalent. The various storm layers have bonded quickly. Observers have reported varied test results (some planar and sudden) just above the early-December crust which is now  3.5 feet or more below the snow surface on slopes above 5,000ft. So far no avalanches have been reported on this crust but it's something to keep an eye on.

On Saturday morning, December 12th, an avalanche fatality occurred in Silver Basin area of Crystal Mountain Ski Resort. Our deepest condolences to the family, friends, and community. See the accident report for details. 

Uphill travel reminder: Check in with your local ski area this weekend regarding terrain access and parking updates. For the SPMR uphill hotline call 206-812-7847. 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