Bulletin d’avalanche

Snoqualmie Pass

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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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 snowpack is about to change drastically from what we have experienced over the past two weeks. Widespread avalanche activity is expected for the duration of the storm and avalanches could break in surprising ways. Don’t treat this like any other loading event. Let the snowpack undergo its transformation before you think about heading toward avalanche terrain.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    2

    This storm should produce more dense snow than we have experienced lately, creating an upside down snowpack primed for slab avalanches. We expect most slabs to be reactive at the new/old snow interface or on recently buried layers in the upper snowpack. Slabs will be thicker and possibly more sensitive in wind-loaded terrain and there is plenty of loose snow available for entrainment to help any slide grow large. Shooting cracks or whumpfing collapses are red flag signs that the snow is unstable and you shouldn’t ignore them. Recent observations indicate that this problem may extend into areas commonly referred to as “safe” on high hazard days such as treed areas, and that these avalanches could break in surprising ways by propagating widely or connecting terrain features. Monday is not a day to be traveling on slopes over 30 degrees.

    (1/2/2022)

    Shooting cracks and whumpfing collapses were observed at Snoqualmie Pass as a storm approached and stiffened snow surfaces on 1/2/22. These are red flag signs of instability and should drive you to lower angled terrain.

    Photo: Robin Pendery

Avalanche Discussion

The transition to an unstable snowpack began on Sunday as a potent winter storm approached Snoqualmie Pass. A Wind Slab avalanche triggered by a cornice fall had an 18" crown and was responsible for a skier being buried at Alpental Ski Resort. Luckily this individual was unharmed. As the day progressed, observations from professionals and recreationalists alike indicated a new period of graupel fell, as well as shooting cracks, whumpfing collapses, and human-triggered D1 Wind Slabs. These are all red flag signs of instability letting us know that the snowpack is going through a transformation.

NWAC forecasters in the Kendall Mountain area on Sunday found multiple potential points of failure in the upper snowpack for this incoming storm to test.  We now have a barely buried graupel layer to consider as well. We do not anticipate any slides deeper than the Solstice Crust that is buried about 3 feet below the surface. Although the bulk of the natural cycle may happen overnight Sunday into Monday, instability should linger into the daylight hours and continue producing avalanches. This will not be your standard PNW storm cycle and it is not your standard high hazard day, so you need to treat it as such by dialing it back.

Régions couvertes