Avalanche forecast

Central Cascades

Central Oregon Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Heavy snowfall and breezy conditions on Wednesday will keep the avalanche danger elevated.  Avalanches large enough to bury or injure a rider remain likely on slopes that the wind has blown new snow onto.  These conditions are most prevalent high in the alpine and near treeline where the wind can transport the most snow, and on slopes that face any direction other than West and Southwest.  On Monday, a large avalanche claimed the lives of two riders.  Most avalanche activity below treeline will be relatively small, but large avalanches remain possible on steep unsupported slopes.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    Wind Slabs have been steadily growing despite a brief lull in our stormy weather.  With heavy snowfall and Moderate winds in the forecast for Wednesday, of course Wind Slabs will continue to be a concern.  On some slopes, Wind Slabs may overlay weak snow from last week, and the resulting avalanches may be larger and propagate farther than you might otherwise suspect.  Increasing your margin of safety on Wednesday is a good idea.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2.5

    There could be two flavors of Storm Slabs to be aware of on Wednesday.  The first and most likely are shallow instabilities that exist in the newest snow.  With relatively small amounts of new snow (much less than a foot of new snow), and generally cooling temperatures, the hazard from these "new" storm slabs is on the lower end.

    The other flavor is Storm Slabs that could fail on last week's dry powder, which is currently buried 40-55 cm. and will be deeper tomorrow with the new snow.  This is the Storm Slab that killed two riders in Happy Valley on Monday.  These avalanches remain unlikely except in steep, unsupported terrain.  I was surprised to see the avalanche in Happy Valley on the slope that it occurred on.  Given my surprise, and the resultant uncertainty, I am dialing back my terrain choices to more conservative slopes.  Don't be lulled onto large, steep slopes by Resistant Planer test results.  The weak layer in question won't be around for long, so just take it easy for a few more days.

Avalanche Discussion

On Monday, an avalanche (size 2) occurred in Happy Valley at 6,700 ft. on a South slope.  This avalanche claimed the lives of both riders involved.  The slide appears to have failed down 45-50cm. on weak snow that was buried last Thursday (2/13).  This weak snow exists throughout our below treeline terrain and possibly at higher elevations.  It is comprised of the broken and intact large snowflakes that exist where last Thursday's (2/13) snow overlays the older snow.  It doesn't seem to be weak enough to have resulted in a large avalanche cycle, and for the most part I've been getting test results that are neither the pops nor drops that we associate with avalanche activity.  On the steep South facing slope of the accident, it overlaid a melt-freeze crust that developed during the high pressure.

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