Avalanche forecast

Central Cascades

Central Oregon Avalanche Center
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Avalanche danger

Fri
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Triggering avalanches will be likely in wind drifted snow on northerly, easterly, and south facing slopes near and above treeline. Avalanches in the new storm snow will also be likely on all aspects and anwhere the wind has not removed the recent snow. Triggering avalanches on deep weak layers at mid and upper elevations are unlikely, but will be large and have huge consequences if they  do occur....steep and unsupported slopes with shallow rocky areas as potential trigger points are places to consider avoiding.

Avalanche problems

  • Wind Slabs

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

    Wind slabs are most sensitive to triggering during the storm and just after the storm. Use careful evaluation to determine which slopes have become wind loaded and the depth of wind deposited snow. As wind slabs become deeper, avalanches can become larger. As more snow falls, along with sustained winds out of the west and southwest, wind slabs will continue to build on lee slopes. In some places, the snow that began falling on Tuesday may be sitting on buried surface hoar. Observers also found a crust under the new snow with very weak snow below it. These layers may cause wind slabs to propagate wider and run farther than what we usually see. Look for signs of cracking in wind drifted snow and recent avalanches as indicators of unstable snow. 

    Clearings in the forest, and areas with dead trees can be susceptible to blowing snow and wind slabs. 

  • Storm Slabs

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

    The amount of new snow over the last 24 hours has varied across the range from 10-18". On Wednesday, small storm slab avalanches (4-5" crowns) were observed on steep rolls on east facing slopes below treeline in the Todd Lake area. Another observer on the east side of the range reported slab avalanches, up to 18" deep, in the new snow were easily triggered on north and east facing slopes near and below treeline on slopes over 30 degrees steep. In some places, the snow that began falling on Tuesday may be sitting on buried surface hoar. Observers also found a crust under the new snow with very weak snow below it. These layers may cause storm slabs to propagate wider and run farther than what is usally expected. With more snow coming in, storm slabs will continue to build. Use small steep/convex test slopes to look for cracking in the slab ans/or small avalanches to gather more information about how the storm slab is behaving. 

     

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3

    Weak layers formed formed earlier in the season are now down 140 - 200 cm (or deeper) below the surface. Multiple layers of faceted snow and buried surface hoar are now deep enough where the chance of us triggering an avalanche on these layers is unlikely but not impossible. An avalanche occurring on one of these deep layers would be very destructive. We probably won't get any feedback in the form of collapses or whumphs associated with this problem and with the exception of digging down through the entire snowpack, we may not know if it is under us or not. Increase your margin of safety by avoiding trigger points such as shallow rocky areas in steep terrain. 

Avalanche Discussion

Be cautious of recently formed cornices at ridge tops hanging over lee slopes. New cornices can be fragile and break easily under the weight of a person. 

With multiple avalanche problems with overlapping distributions, remember anytime you have uncertainty in the snowpack, increase your margin of safety by sticking to slopes less than 30 degrees steep. 

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