Bulletin d’avalanche

Central Cascades

Central Oregon Avalanche Center
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Danger d’avalanche

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

Points saillants

Avalanche danger will increase as the day progresses. As more snow falls and the wind picks up, triggering avalanches in wind drifted snow will be likely near treeline and above treeline. Triggering avalanches in the new storm  snow will be possible as recent snow stacks up to 8" or more. If you have uncertainty in the stability of the snowpack, choose slopes less than 30 degrees steep to minimize your exposure to avalanches.

Problèmes avalancheux

  • Wind Slabs

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

    Wind speeds will increase on Friday. The likelihood and size of this problem will increase in the second half of the day as precipitation ramps up. Some terrain features will collect more blowing snow than others. Not all slopes are the same and it is important to use your evaluation skills to monitor how deep slabs are. As slabs become deeper, avalanches can become larger. Utilize small test slopes to monitor depth of wind slabs and look for signs of unstable snow such as shooting cracks. Recent avalanches are also a great indicator that triggering avalanches can happen.

    Keep an eye on blowing snow and wind slab development in areas of dead forests and clearings in areas you typically think of as below treeline. 

    Prior to this storm cycle, observers found surface hoar in a few places near treeline; wind slabs building over surface hoar will have the ability to propagate wider and run farther than normal. 

    Archive Photo (Elliott Reed)

    Example of shooting cracks in wind drifted snow. 

     

  • Storm Slabs

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

    Timing is involved with this problem and directly related to the amount of incoming snow. As snowfall ramps up in the second half of the day, small storm slab avalanches could come into play. As you see 8" or more of recent snow, storm slab avalanches should be on your mind. Be cautious in steep, convex, and unsupported terrain. Be aware of the the terrain below you and think about the consequences of going for a ride. Using small and safe test slopes are a great way to check for the reactivity in the storm slab. 

    Previous to this storm cycle, observers found surface hoar in wind/sun protected areas. I did not find any buried surface hoar today, but I suspect there are patches of it out it out there under the recent snow, especially in those north facing, shaded, and protected glades near treeline and below treeline. Buried surface hoar can create a sensitive weak layer in the snowpack and can lead to avalanches breaking wider and running farther than usual. 

Avalanche Discussion

Small cornices may build at ridgetops. Be cautious when approaching ridges especially in areas with low visibility. Avoid breaking through a cornice and falling down the slope below.

Régions couvertes