Elkhorns

Stable avalanche conditions will remain today. Remember that low danger does not mean no danger and buried weak layers still exist. Your greatest chance of triggering an avalanche will exist in upper-elevation terrain that is very steep, shallow, and shaded. Watch for loose snow sloughing and small, soft slabs if you see more new snow than forecasted. 

This forecast is sponsored by: Wallowa County SAR.  

What's going on with our snowpack? Warm temperatures over the past several days have consolidated the upper snowpack.  The warm temperatures and sunshine have melted more low-elevation snow and exposed more objects in the higher-elevation terrain. These changes to the surface snow have not affected the snowpack below. Facets and Depth Hoar are still present sandwiched between melt-freeze crusts and at the ground. You can see observations that showcase the Persistent Slab avalanche problem in the Elkhorns, Southern Wallowas, and Northern Wallowas.

Here's another great observation for the Northern Wallowas.  

How will the incoming weather change the situation?  Anytime we add a new load to the snowpack, Mother Nature is allowing us to learn more about how strong or weak the structure of the snowpack truly is.  Think of adding new snow to weight lifting.  If we are doing the bench press and we slowly add weight it's like the snowpack receiving a few inches each day over a week.  Conversely, if we start slamming 45# plates on the bar, it won't take long before we are left gasping with the bar on our chest.  The snowpack often behaves the same, as a significant load in a short period tips the stress-to-strength ratio.  Weather forecasts are showing some decent accumulations this weekend and into next week.  We may find ourselves with a new buried weak layer (surface hoar) in some locations if the wind didn't blast it.  We'll keep you posted.

State of the snowpack: Small amounts of snow that fell during our prolonged autumn have rotted 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. While the upper portion of the snowpack feels sturdy, there are thin layers of weak snow around the melt-freeze and rain crusts and the base of the snowpack.  This snowpack structure creates a Persistent Slab avalanche problem.

The Persistent Slab avalanche problem is a tricky one. You can't see it by visually scanning the mountains. It isn't obvious on the surface of the snow. Other clues like cracking, collapsing, and whumpfing may not occur. Even if you dig down and conduct stability tests the results can be hard to interpret and inconclusive. This is the dreaded low likelihood, high consequence scenario. You might not trigger one of these avalanches or even know it is there, but if you do, it will break near the ground and take all the dense snow on top of it with it.

The best way to avoid getting caught in one of these slides is to avoid where they exist. That means anywhere snow has stuck around since fall, has more snow on top of it, and is steeper than 30 degrees. Given the shallow snowpack everywhere, colliding with obstacles would make taking a ride in an avalanche particularly nasty. Many rocks, trees, stumps, and down timber are on the surface or very shallowly buried.

Surface Conditions: It's good to consider the status of the current snow surface as we enter a period of unsettled weather.  Over my travels the past couple of days, I found a plethora of snow surfaces.  On solar aspects, there was a melt-freeze crust, and on shady aspects near surface facets (sugar snow) and surface hoar near the treeline.  Above the treeline, the wind had stripped and scoured the snow surface in places.  All of these different surfaces will determine how well the new snow bonds, or how strong or weak the snowpack will be as we start to receive new snow.  All of this variety adds to uncertainty, and as the uncertainty increases so should our margins.  

If you get out to slide or ride please send us your observations! A picture or quick description of the conditions you encountered is SO helpful in creating these avalanche forecasts for you.