Avalanche forecast

Central Cascades

Central Oregon Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avalanche danger will rise through the day on Saturday as new snow accumulates. Triggering avalanches will be likely in wind drifted snow on lee slopes near and above treeline. The incoming snow will add stress to the weak layers in the old snow, specifically on northerly and east slopes near and above treeline. This is a day evaluate conditions, make careful terrain decisions and don't hesitate to move to lower angle slopes less than 30 degrees to reduce your exposure to avalanches. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    This problem has been a tricky one and the key term we have been using is 'variability'. So far there have not been any reported avalanches on the multiple persistent weak layers in the snowpack. New snow will add some stress to the snowpack, especially in terrain that receives heavy wind loading. Observers have been finding two layers of buried surface hoar. One is down  20-25 cm, and the other is down 45-60 cm (prior to incoming snow on Sat.). There are also multiple layers of faceted snow in the upper 60 cm of the pack. We have been calling this problem unlikely but I am moving it to possible with the incoming snow.  Persistent slabs can propagate across terrain to a larger extent compared to other slab types. Digging and checking for the presence of these layers can help a lot in your decision making process. If you observe slope collapses and/or hear the 'wumph' sound, these are good indicators that these layers are active.

  • Loose Dry

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    The incoming snow will be light, cold. This is the problem everyone looks forward to, but keep an eye on where dry loose snow can run; especially in steep terrain and gully features where snow tends to flush. Most of these avalanches will be small, but be aware of where you can get knocked off your stance in steep terrain and pushed into terrain traps. This problem has the chance to be everywhere that the snow has not been scoured away by the wind. 

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    The size of wind slabs will build through the day. The temperature will remain cold and new snow will be light and easily moved by the wind. The weather forecast is calling for strong wind speeds; blowing snow will move to places that don't normally get wind loaded. Use your observation skills and check out what slope features are becoming wind loaded. Monitor the depth of wind slabs. Use low angle lee slopes to check on the depth of wind slabs before committing to avalanche terrain. As wind slabs become deeper, avalanches can become larger.

    With strong winds possible, this will be a day to be cautious in places that don't normally get wind slabs such as large clearings below treeline and areas with dead stands of trees.  

    Archive photo from pro observer Jonas Tarlen.

    Wind slab avalanche. Notice the surface texture above the crown. Wind slabs often have a wavy surface appearance. Use this visual clue to identify where wind slabs are inthe terrain.

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