Avalanche forecast

Elkhorns

Wallowa Avalanche Center
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Avalanche danger

Mon
Alpine
2 · Moderate
Treeline
1 · Low
Below
No rating
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

New, light snow has fallen on weak snow surfaces and hard crusts. Humans venturing into steep mid and upper-elevation terrain could trigger loose snow sloughs or small slabs.  Watch for areas of drifted snow and avoid terrain traps where even small slides could have harsh consequences.

This forecast is sponsored by: Wallowa County Gamblers Snowmobile Club.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Winds out of the SW at the onset of yesterday's storm have formed soft wind slabs in the above treeline zone. Moderate winds out of the NW will redistribute snow that fell yesterday building new slabs. This combination of winds makes slabs most likely on North, East, and South facing slopes. The new snow fell on a variety of snow surfaces from the December drought. Slick crusts and weak sugary snow on the surface could make triggering one of these slabs easier.

    No avalanche danger rating has been applied to the below treeline band due to the lack of sufficient snow cover at that elevation.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1–1.5

    Weak snow persists one to three feet below the surface. Although unlikely, slabs involving this snow have a  chance to be initiated in extreme terrain. Causing an avalanche in the new snow could be an effective trigger for avalanches failing deeper in the snowpack.

    No avalanche danger rating has been applied to the below treeline band due to the lack of sufficient snow cover at that elevation.

     

Avalanche Discussion

New snow fell on a variety of snow surfaces from the December drought. Slick crusts and weak sugary snow on the surface could make triggering one of these slabs easier. Evaluating the bond between the new and old snow will be key in avoiding avalanches. This can be done with quick pits you dig with your hand or by getting out a shovel and digging down.

New snow and the Persistent Slab problem: Generally light accumulations of snow over the past couple of days have not added a tremendous load to the snowpack. This incremental loading is important to track because we never really know how much of a load it will take to wake up the Persistent Slab problem. We do know that any weight (new snow) that is added on top of these weak layers makes them more likely to fail. Your index of suspicion should be increasing as the snowfall totals do. 

Big picture: Snow that fell during our prolonged autumn has rotten and weakened. On top of this several rain storms (12/4) or periods of above-freezing temperatures have created crusts. Snow depths range from nothing in the below treeline zone to 115cm/3ft+ in the above treeline terrain. Warm temperatures since Christmas have consolidated the upper snowpack. While the upper portion of the snowpack feels sturdy, there are thin layers of weak snow around the melt-freeze and rain crusts and at the base of the snowpack.  This snowpack structure creates a Persistent Slab avalanche problem. Facets and Depth Hoar are present sandwiched between melt-freeze crusts and at the ground. You can see observations that showcase the Persistent Slab avalanche problem in the (1/4)Elkhorns,  (1/3) Northern Wallowas, and (12/29) Southern Wallowas. 

While it is currently unlikely you will trigger one of these slides, the consequences of doing so would be dire. The entire snowpack could fail at the ground and take you with it.  

 

 

Please let us know what you see while you're out recreating.

 

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