Avalanche forecast

Central Cascades

Central Oregon Avalanche Center
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Avalanche danger

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

Triggering avalanches in wind drifted snow will be likely on Thursday near and above treeline on northerly and easterly facing terrain. Triggering avalanches on weak layers deep in the pack at mid and upper elevations are unlikely, but will be large and destructive 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
    Possible
    Size
    1–2

    Most wind slab avalanches will be small, but some isolated terrain features may catch enough blowing snow to produce large avalanches if triggered. With more snow coming in overnight and a few inches possible on Thursday along with sustained westerly winds, wind slabs will continue to build. Wind can deposit snow many times deeper than the storm accumulation. Wind slabs are most sensitive to triggering when they are fresh. Be cautious on wind loaded slopes especially in steep terrain and above terrain traps. Monitor how deep wind deposited snow is stacking up and remember as drifts become deeper, avalanches can become larger. Look for cracking in the slab on small test slopes or previous avalanches as signs of unstable snow. Natural avalanches will be unlikely but not impossible. Look for signs of wind slabs below treeline in areas of dead trees or clearings. 

    (1/24/2024)

    Skier triggered cornice triggered a wind slab avalanche in the Tumalo bowl on Wednesday (D1, east aspect near treeline.) The debris was not deep but ran several hundred feet down the bowl. The crown was 12" - 20"

    Photo: Aaron Hartz

  • Deep Persistent Slabs

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

    I got a look at the deep snowpack today. The December 22 buried surface hoar is still visible in the pack down 65" below the surface. This layer failed during a deep tap test with resistant results. The old faceted snow layers show signs of gaining strength and have rounded or are mostly rounded. I want to keep this problem up for the time being until we get more information from other areas regarding the deep pack. 

    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. 

    Checking on the deep layers in the pack on a NE aspect near treeline. The Dec. 22 surface hoar is still in the pack.  At this location, the old facet layers have mostly rounded and gained strength.

    Photo: Aaron Hartz

Avalanche Discussion

The most recent crust in the upper pack, now down about 16" below the surface had no failures associated with it during snowpack testing on a NE aspect near treeline. 

Cornices were growing on Wednesday. The ones I saw were very thin and easily broken. Be catious when approaching ridge tops. Stepping out onto a cornice can lead to an unexpected air drop and can have big consequences on steep slopes or above terrain traps such as cliffs. 

 

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