Bulletin d’avalanche

Central Cascades

Central Oregon Avalanche Center
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Danger d’avalanche

Tue
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Dangerous avalanche conditions will perist into Monday.  Avalanches will be most likely on steep slopes where the wind has deposited our new storm snow (north, east and south slopes near treeline and above).  Persistent weak layers from before this storm may cause avalanches to be large.  Monday is a good day for conservative decision making.

Problèmes avalancheux

  • Wind Slabs

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

    Today I observed a small wind slab avalanche near treeline on a northeast slope, as well as obvious cracking in wind deposited snow.  These wind slabs need time to resolve themselves.  Increasing west winds throughout the day on Monday will continue to transport and pack snow onto east slopes; north and south slopes may also be affected.  Wind Slabs may propogate farther than usual if they are failing on weak faceted snow from before the storm, and they could even step down to peristent weak layers within the older snow pack.

    cracking in wind deposited snow on a small test slope, near treeline, north

    Photo: Gabriel Coler

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–2.5

    Before this storm, things were pretty darn dry and shallow around our mountains.  Cold clear nights provided the opportunity for several perisistent weak layers to develop on and within this early season snowpack.  Today I experienced many substantial collapses (whumphs) in north facing terrain at treeline.  These were most likely caused by weak, faceted snow directly beneath our latest storm snow.  We have also been tracking 2 layers of surface hoar and variable near crust facet layers.  These layers are getting progressively deeper.  I for one am avoiding big, steep slopes until after this storm cycle (whenever that is).  Hand shears have been a great tool for assessing the bond between the storm snow and old snow.  If you want to check out the deeper surface hoar or crust/facet combo you'll want to resort to your compression test, and by Monday afternoon you'll need to dig 1 - 1.25 meters.  It is hard for us to give precise depths at this point because of signifcant variations in storm snow accumulation.

  • Storm Slabs

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

    Monday's new snow will be accompanied by rising temperatures.  Snow that falls during warmer temperatures is generally heavier and more cohesive, which often leaves us with what we call an "upside down" snowpack (hard over weak layering).  I expect these avalanches to be relative shallow given the modest snowfall totals for Monday.    Be cognizant of terrain traps that could accentuate the consequences of even a small avalanche.

Régions couvertes