Bulletin d’avalanche

East Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

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

Points saillants

Consider the potential for avalanches- both small and large, before entering complex terrain. Snow may be easily transported into wind slabs as another round of weather comes through. Look and listen for signs of instability, like whumphing collapses, and shooting cracks. 

Problèmes avalancheux

  • Wind Slabs

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

    Look for signs of recent and active wind drifted snow such as sharp drifts, small cornices, and wind rippled snow. If you can observe areas that are freshly affected by wind, steer around them. Small, shallow avalanches are possible within recently drifted snow. Use caution, especially on very steep slopes that may have increased consequences if getting caught or carried by a small slide. You can check how the snow is reacting by using small, inconsequential test slopes before entering larger slopes. Watch for shooting cracks and recent avalanches as indicators of danger.

    Deeper and more surprising avalanches may be unlikely, but not impossible. We have limited information on the upper elevation snowpack, but we do know that deeper layers are a concern in the neighboring East North zone. Listen for whumphing collapses as you travel, they're the snowpack's way of telling you that a deeper layer is unstable. Consider avoiding complex or unsupported terrain at upper elevations. You can dig down and use snowpack tests to check how snow is bonding to the crusts from late November and early December.

    Drifts covering the skin track a few hours later are a sign that wind is drifting snow. Photo: Matt Primomo

Avalanche Discussion

An upslope storm on Monday brought up to 8 inches of snow to the area, including to the valleys and foothills. On Tuesday I found evidence of a few small loose dry avalanches that likely ran during the burst of heavier snowfall. Since December 8th significant new snow has fallen on various surfaces, including rain crusts, soft snow, or firmer recently wind deposited snow. The snowpack depth and structure vary significantly from west to east. Near the Cascade Crest, you may find areas with up to 5 feet of snow on the ground, while further east near Mission Ridge the snowpack may be only 1-2ft deep. 

A pair of crusts from late November and December 8th may be found at higher elevations of the zone near the crest. These crusts may harbor weaker snow above them and are a source of uncertainty at this point in the season.

On Tuesday, an observer reported weak, faceted grains at the base of a shallow snowpack at Mission Ridge. These 'basal facets' will be worth considering with any thickly drifted wind slabs, and as we head further into the winter.

In many areas, the snowpack is still very shallow. If you're recreating on snow be aware of hidden logs, sharp rocks, and open streams.

Régions couvertes