Avalanche forecast

Central Cascades

Central Oregon Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Triggering a slab avalanche in wind drifted snow near and above treeline and storm snow at mid and lower elevations will be possible on Friday.  Evaluate slopes for signs of where wind transported snow has been deposited. If you observe cracking in the surface snow, signs of unstable snow, and/or encounter previous slab avalanches, increase your safety margin by moving to lower angle terrain options less than 30 degrees steep.

Avalanche problems

  • Wind Slabs

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

    Existing wind slabs have been on the ground for up to 24 hours but it is too soon to write them off. With an abundance of low density snow on the ground, westerly and SW winds will continue to move snow to lee slopes and continue to build wind slabs. This type of slab typically forms below ridge tops and high points and on other features that catch wind blown snow. Look for visual clues such as a wavy, ripply, or pillowy surface texture to indicate where wind slabs have formed.  Fresh cornice formation and actively blowing snow are also useful clues to let you know where wind slabs may be present. Wind slabs will not be everywhere so using careful evalutation is key.  

     

  • Storm Slabs

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

    I was ready to take storm slab off the list today because the most recent storm snow was not showing much slab properties. Until I found buried surface hoar on east facing slopes below treeline. I am not ready to add a 'persistent slab' problem, but the presence of a weak layer like buried surface hoar can make the storm slab problem a little more lively. This is one of those situations where the problem doesn't fit neatly into a box that we can check. Currently the buried surface hoar has only been found (or at least reported) on east facing slopes below treeline and is down 40-60 cm below the surface. Distrubution could be very specific or it could be on other aspects and elevations. I'm leaving this as a storm slab problem for now because any storm snow above the weakness could run as a slab.  

    (12/1/2022)

    Propagation on ECT test down 60 cm on buried surface hoar layer.

    Photo: Aaron Hartz

Avalanche Discussion

The buried surface hoar I mentioned above in the 'storm slab' problem discussion was found at Todd Lake in multiple east facing glades below treeline. I got repeated propagation in extended column tests. I did not experience any collapsing or whumphing while moving through the terrain and I was not on terrain steep enough to initiate an avalanche. We will continue to check on the distribution and activity of this layer. 

With cold temperatures and low density surface snow, some shallow dry loose avalanches may be observed in steep terrain, but they will likely be small.

The snow has really been stacking up, but keep looking for those early season hazards such as rocks and logs lurking just below the surface.

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