Bulletin d’avalanche

Central Cascades

Central Oregon Avalanche Center
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Danger d’avalanche

Thu
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

Avalanche danger will remain elevated as recently formed Wind Slabs take time to settle.  Numerous avalanches were observed on Tuesday up to size 1.5.  They were mostly near treeline and on North slopes.  Take time to evaluate recent wind loading if you are traveling at higher elevations.  I triggered a D1 avalanche today that failed on burried surface hoar.  This weak layer is likely only present on isolated North facing terrain, and may have become more reactive with the increased load of recent snow.  When in doubt choose more conservative lines and avoid trigger points.

Problèmes avalancheux

  • Wind Slabs

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

    The latest round of snowfall left us with an additional 40-50 cm of new snow!  During the storm winds were moderate from the South and East.  Natural and human triggered Wind Slab avalanches were observed on North slopes near treeline and in open terrain.  These wind slabs will require more time before they become unreactive and will continue to be likely on Wednesday.  Winds on Wednesday are forecast to shift to the West but also decrease dramatically.  I would expect the greatest potential for continued blowing snow to be on alpine slopes.

    (3/28/2023)

    Natural Wind Slab Avalanche, North, approx 7,400 ft.

    Photo: Gabriel Coler

  • Persistent Slabs

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

    On Tuesday I triggered an avalanche that failed on a layer of buried surface hoar down 70 cm. (see picture).  The slope faced NNW and was at 7,240 ft.  We have not found this layer to be widespread throughout the terrain.  Recently I have found it below and near treeline on North slopes, and this is the first instance of an avalanche that we can attribute to this weak layer.   Remember that surface hoar forms on slopes that are Cold Clear and Calm.  It is most often preserved on North slopes where it is protected from the sun and wind.

    If you are choosing to ride steep, North facing terrain that checks the boxes for Cold, Clear and Calm, it is worth doing some digging and a few compression tests first.  I'll be choosing more conservative lines, and avoiding likely trigger points when on steeper slopes.

    To learn more about surface hoar or Persistent Slab avalanches check out these links.

    (3/28/2023)

    NNW, 7240 ft. D1 due to length of slope, 70 cm crown

    Photo: Gabriel Coler

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