Avalanche forecast

Central Cascades

Central Oregon Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

On Wednesday it will remain possible to trigger a Wind Slab avalanche on slopes that the wind has blown snow onto.  While these Wind Slabs are trending towards being less reactive they likely need more time before we can consider them a thing of the past.  Wind Slabs are most likely where the wind was able to blow freely near treeline and at alpine elevations, and could exist on any aspect given the shifting winds associated with our recent snowfall.

Avalanche problems

  • Wind Slabs

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

    Wind Slabs occurr when the wind blows snow onto sheltered slopes below ridgelines and behind crossloaded features.  The wind not only moves the snow around (making it particularly deep on these lee slopes), it also breaks up the crystals so that when they come to rest they often pack together into a more cohesive slab.  When this slab overlays weaker snow, Wind Slab avalanches can occurr.

    On Tuesday I observed large collapses in wind drifted snow.  In the last 48 hours winds have been from the east, south, west, and even just north of west.  This means that we are seeing some unusual loading patterns throughout the terrain.  On slopes that are not affected by the wind we have 20-25 cm. of new snow with a stout crust beneath.  By using this crust as a landmark it is easy to note changes in this new snow depth as you travel through terrain.  Be wary of deeper areas of wind deposited snow especially if they exist on steep convex slopes.  You can often identify new wind slabs by their soft, pillowy appearance.

Avalanche Discussion

On Monday there were observations of widepread instability in the shallow storm snow at Tam Rim.  Today in that same terrain, I found only the most isolated pockets of instability.  As a result of these observations, and given the shallow nature of the avalanche problem to begin with I am removing Storm Slabs from the problem list.  The primary avalanche hazard on Wednseday will be in deeper wind loaded snow which needs a bit more time to stabilize.

Regions covered