Avalanche forecast

Elkhorns

Wallowa Avalanche Center
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Avalanche danger

Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Highlights

We have generally safe avalanche conditons in the Elkhorn Mountains. However, increasing southerly winds today will build pockets of reactive wind slab on the north aspects at and above treeline. Avoid areas of recent wind deposition >35 degrees and potential trigger points like convex rollovers, wind pillows below cliff bands, and cross-loaded terrain features mid-slope.

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Avalanche problems

  • Wind Slabs

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

    While the winds were light out of the SSE last night they are forecast to increase today with the coming storm. Expect south winds blowing teens with gusts in the 20's. These moderate winds may create isolated pockets of reactive wind slab 1-2' thick above treeline.  You can identify wind slabs by looking for smooth textured pillows below ridgeline and on the leeward side of terrain features like ribs and gullies. Many of the most recent avalanches reported or witnessed with the last storm cycle pulled out on steep connected aprons below cliff bands. Avoid potential trigger points like steep wind-loaded slopes > 35 degrees, convex rollovers, and unsupported slopes above and below cliffs.

Avalanche Discussion

Wet Loose Avalanches - A disappearing Concern

The incoming storm system is bringing cloudy conditions to our area this morning. The lack of solar influence and radiation input into the snowpack today will significantly decrease the chances for wet loose avalanche activity on steep south-facing terrain. Be vigilant at lower elevations as the warm temps may keep this problem type on your radar.

The Coming Storm

As avalanche forecasters we are always mindful of what is going on at the snow surface during the intervals between storms. The longer the snow surface is exposed to the elements - the weaker it becomes. We've had a handful of glorious sunny days this past week. While this weather largely produced high fives, smiles, and relatively stable conditions it did leave us with variable surface conditions across our local mountain ranges. On south-facing slopes exposed to the sun we now have slick melt-freez crusts. In the alpine, we have hard wind scabs where the south winds stripped off windward aspects. In my travels to Wing Ridge and the Northern Elkhorns the last few days I've observed widespread surface hoar formation on a variety of shady and protected slopes up to 8,000' in elevation. On NW-N-E slopes, at and below treeline, the powder turn have been glorious. What do all these variable snow surface conditions mean when we start getting more snow? Let me give you a breakdown.

Slick Crusts on South-Facing Terrain

All the sunshine over the last few days has created stout melt-freeze crusts on southerly aspects at all elevation bands. Any new snow is not going to bond well to these slick crusts. As snow totals creep above a few inches to over 8" in total by the end of Monday, there will be the potential for natural and human-triggered dry loose avalanches on steep slopes. While these slides may be shallow, the danger is once released they will pick up speed quickly and could have you being the proverbial ping-pong ball - bouncing off trees, rocks, and over cliffs. Bodily trauma...that is the worry with these dry loose avalanches. And it is still possible to be buried several feet deep by a 6" deep avalanche, especially if that slide takes you into a terrain trap like a gully or piles up behind a tree fence.

Surface Hoar Formation

In my travels to the Northern Wallowas and Northern Elkhorns the last few days I've observed widespread surface hoar. The relatively clear, cold, and calm nights have been the perfect conditions for surface hoar formation. I'm seeing some pretty big crystal sizes - up to 9mm. While these feathery crystals are cool to look at on the surface they become a pesky persistent weak layer when buried. I observed well-developed surface hoar on a variety of shaded and protected slopes up to 8000' in elevation. I anticipate the light winds will allow the surface hoar to be buried and preserved with the new snow coming in tonight and through Monday. This persistent weak layer will become reactive where snow totals exceed 6" or more. It may take a day or two for the new snow to consolidate from fluffy pow-pow to be a more dense slab capable of propagating a fracture - but it will happen. The tricky thing with buried surface hoar is that it isn't everywhere. It will be persisting in certain places in the terrain. Be wary of potential trigger points on sheltered north-facing terrain below treeline. Avoid convex rollovers (> 35 degrees), unsupported slopes above cliff bands, weak zones below cliff bands and rocky outcroppings, and find terrain with lower consequences if it was to produce an avalanche.

The Best Snow

As many of you discovered this past week, good snow is holding strong on more protected north-facing slopes below treeline. This will keep being the place to find good quality turns and riding conditions. I'll caveat that by mentioning buried surface hoar. Be mindful of its possible existence. When it doubt - dig. Dive into the snowpack and look for the possible buried surface hoar below the new snow. If you are still unsure, then increase your margin of safety by sticking to lower angle terrain.

 

 

 

 

 

 

 

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