Bulletin d’avalanche

Stevens Pass

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Ridgetop winds should transport the new snow into shallow but reactive wind slabs. Warming temperatures and light rain above pass level may create wet loose hazards. Look for signs of instability throughout the day related to both of these avalanche problems, and choose appropriate terrain for the bump in avalanche danger. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    A handful of inches of new snow over weak surfaces or slick crust is likely to create isolated areas where you could trigger a slab on Saturday. You're most likely to find thicker and reactive slabs near and above treeline, where westerly winds into Saturday morning may redistribute the newly fallen snow.

    Make sure to observe how wind-drifted snow reacts before committing to steep slopes or larger features. Check to see how the new snow is reacting with hand pits, skin track tests, and small test slopes. If you find that drifted snow tends to create long shooting cracks, then expect you could trigger slabs on nearby terrain if it's steep enough to slide. 

    Blowing snow and sharp wind lips above a freshly formed wind slab. Photo: Dallas Glass

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    Wet loose avalanches could run and entrain the new snow on steep and continuous slopes. By saturday afternoon, warming temperatures and perhaps some of the suns energy could turn snow surfaces moist at lower elevation. You'll know when this is starting to happen when the snow surface become sticky, or you see rollerballs occurring naturally from trees and on steep slopes. 

    If you find signs of wet loose avalanches, then anticipate the hazard before going on or underneath steep slopes at those elevations. Watch out for terrain traps like gullies and creek beds where even a small loose slide could pile up some deeper debris.

    A very small wet loose avalanche below treeline.

    Photo: Lee Lazzara

Avalanche Discussion

The mid winter dry spell has come to a close, and the mountains are picking up some new snow once again. The longer the dry spell, often the less likely the new snow is to bond well to old surfaces. This was about a week since the last snow, fairly substantial for early February on the crest of the Cascades. A blast of arctic air weakened many snow surfaces into near surface facets on shaded slopes (see photo below). We're not sure yet how this new snow will react yet, but chances are it won't bond well. Recently buried snow surfaces include a range of conditions including small near surface facets on sheltered northerly aspects, slick sun crusts on slopes that receive direct sun, and various degrees of stiff wind packed snow. Some areas held isolated patches of recently buried surface hoar on shaded slopes. Below 3,500ft you can expect firm and icy crusts beneath whatever new snow falls.

There are a couple crusts in the upper snowpack, one from January 27th (often thin and brittle) and a more stout, clear ice lens that formed around the MLK holiday weekend. This one is about 1 foot below the surface, and the cold and dry recent weather has contributed to weaker snow above and below it. As new snow begins to add up, this creates a weak structure that we'll have to watch closely. 

Régions couvertes