Bulletin d’avalanche

Elkhorns

Wallowa Avalanche Center
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Danger d’avalanche

Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

The allure of sunny skies and fresh snow should not blind you to the reality that human-triggered avalanches are possible in specific terrain features. A buried persistent weak layer down 2-3' in the snowpack could be triggered by the weight of a rider on north-facing terrain near steep convex rollovers, unsupported slopes above and near cliffbands, and on wind-deposited slopes close to ridgeline. Wind-drifted snow will form sensitive slabs on the leeward side of ridges at upper elevations.  Signs of wind-affected snow include dune-like formations, drifts, plumes, and cornice growth.  Additionally, there is the potential for south-facing and rocky terrain to produce small wet loose avalanches on steep > 35 degree slopes at low to mid elevations in the afternoon in the coming days as temps ramp up. 

It is with profound sadness that we report an avalanche fatality occurred on 3/6 in the Northern Elkhorns. Our backcountry community is small and we understand the tremendous grief many are experiencing. Our thoughts and prayers go out to all affected.  An accident report will be forthcoming.  A preliminary report can be found below in the forecast discussion.

This forecast is sponsored by Anthony Lakes Mountain Resort. 

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2.5

    Weak snow layers, including buried facets above a thick rain crust and surface hoar, have remained reactive and persistent problems in our snowpack over the past week. The 2/1 buried facet layer sitting atop a stout rain crust was the known weak layer that caused the avalanche on Gunsight Mountain on March 6. It is buried in the snowpack between 2-3" deep above 7000'. The layer of surface hoar buried on 2/26 has been found in the Elkhorns, Southern Wallowas and Northern Wallowas. This layer is also about 2' down from the snow surface. It should be noted that in the Northern Wallowas, a report from Sentinel Peak area, indicates a large and destructive natural avalanche cycle occurred around 3/6.  These layers are located on more north-facing slopes (NW-N-NE) at elevations above 7,000'. WAC forecaster, Victor McNeil found a persistent slab problem in the Northern Elkhorns yesterday. Recreationists should be very leary of traveling on and underneath steep > 35-degree slopes in the alpine. Conservative route finding and selection is a must. Avoid having more than one rider on a slope at a time and space out while traveling.

    Be vigilant...we are still getting results in our snowpack tests that indicate the propensity for fracture propogation on these buried persistent weak layers. The warming temperatures through the weekend could increase the likelihood of triggering this weak layer. If you collapse this weak layer in a shallower area on the slope (say around rocky terrain or wind-scoured areas) or roll over a steep convexity the propagating fracture could trigger a large and destructive avalanche.  Avoid potential trigger points and steep (>35 degrees) convex rollovers, especially near treeline and mid-slope. Surface hoar forms in more open and protected terrain. There is a lot of spatial variability of this layer across the slope and throughout the area mountain ranges. It is hard to see in the snowpack as it is a very thin layer. When in doubt, do snowpack tests, and better yet, choose lower-angle terrain to recreate in. You can always choose to avoid avalanche terrain altogether, and at the very least, ride on aspects where this problem is less likely to exist. 

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    North winds will continue to move snow today onto more southerly terrain near ridgeline.  With plenty of snow available for transport, and winds forecast to be 11-20mph with gusts in the 30's, you should expect wind-drifted snow to accumulate and form into a sensitive slab.  A north wind is a bit unusual for our neck of the woods and you should expect wind slab formation on more south-facing terrain. This could be additionally problematic if dense slabs form on slick melt-freeze crusts. Be leary of reactive pockets of wind-deposited snow on the leeward side of mid-slope terrain features like ribs and gullies. The most common signs of wind-stiffened snow are dune-like formations, drifts, cornice growth, dappled yet firm snow surface texture, and plumes of snow coming off the tops of ridges.  In areas of wind deposition, avoid slopes > 35 degrees, especially near steep convex rollovers and other unsupported slopes.

    Triggering a wind slab could have dire consequences on slopes with weak snow buried 2' or more from the surface.   

    (2/29/2024)

    This is the dappled texture of a classic wind slab. 

    Photo: Wallowa Avalanche Center

Avalanche Discussion

Avalanche Fatality on Gunsight Mountain in the Elkhorn Mountains on 3/6/24

At approximately 4:30 pm on Wednesday, March 6th, an avalanche accident occurred on the north side of Gunsight Mountain (8342′) in the Elkhorn Mountains near Anthony Lakes.  

We are deeply saddened to announce that Nick Burks passed away due to trauma after triggering an avalanche while backcountry skiing with a friend.  Nick was a highly respected snow safety professional and worked for the Wallowa Avalanche Center as an educator and forecaster.  A full investigation and report will be forthcoming in the coming days.  Our backcountry community is small and we understand the tremendous grief many are experiencing. Our thoughts and prayers go out to all affected.

A Celebration of Life for Nick Burks

The first celebration of life for Nick Burks will be held this Saturday, March 16 at Terminal Gravity Brewing in Enterprise, OR at 1 PM.  Please bring photos, stories, poems, and songs to share as we’ll have access to the outdoor stage.  Anyone who knew or was impacted by Nick is welcome to attend.  Another celebration is in the works for later this month in Parkdale, OR.  If you have any questions please email [email protected].

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Persistent Slab Problem:  

What:  Weak snow layers in the form of facets and surface hoar buried during February have awoken and become reactive over the past week.  The 2/1 buried facet layer sitting atop a stout rain crust was the known weak layer that caused the avalanche on Gunsight Mountain on March 6.  See Victor McNeil's observation from yesterday in the Northern Elkhorns. Last week there were observations from the Northern and Southern Wallowas of large to very large natural and remote triggered avalanches.  

Where:  Buried surface hoar has been found intact in sheltered North-NW facing terrain between 7,000'-8,000'.  In some locations, there are two distinct surface hoar layers, one that was buried on Valentine's Day (2/14), and the other on 2/26.  While conducting the avalanche investigation on Gunsight Mountain forecasters found a layer of preserved surface hoar, but this was not the weak layer associated with the avalanche.  In the Western Wallowas around Burger Butte (N-NW aspects 7,300-7,700'), the two mentioned surface hoar layers have been preserved and are producing unstable results in snowpack tests.  

How do we manage it:  When we have spatial variability across this huge landscape it is nearly impossible to predict on a slope scale level what is going on under the surface.  It's not uncommon to receive zero Red Flag warnings including cracking or collapsing of the snowpack, even though weak snow layers are present.  Terrain is the one component we have control over, and where and how we choose to travel in it remains up to us. 

Recommendation:   A good friend and fellow avalanche forecaster from the Sawtooth Avalanche Center described the example of gaining confidence by lack of Red Flags in his forecast discussion, which I recommend reading.  

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Wet Loose Avalanche Problem:

Over the coming days this problem-type will only grow as temperatures creep up each day into early next week. Wet loose avalanches may be human-triggered on steep >35 degree slopes in the PM with daytime warming. This problem type will be most active below 6000' or at lower elevations with no overnight freeze. Potential warning signs of wet loose activity include rollerballs and pinwheels cartwheeling down the slope, sinking up to your boot tops in wet snow, or getting your sled bogged down in a soupy moist mess. Recreationists in the Southern Wallowas should be especially careful traveling up steep canyon gullies and drainages in the afternoon as slopes take heat, become unstable, and potentially unleash a torrent of wet avalanche debris down upon you. The tricky thing about moving up steep drainages, say like above Cornucopia, is that you are consistently in the line of fire as the trails traverse along the bottom of these steep slopes. Avoid this problem by staying off and out from underneath steep > 35 degree slopes in the PM. If you must travel under suspect slopes, please spread out and go one-at-a-time. While these slides may be small, they do have the potential to take you off your feet or sled and carry you into dangerous hazards like trees, rocks, and over cliffs. 

Final Note: This is the time of year when extra caution should be given to overhanging cornices. As temperatures rise and the sun's power grows more intense cornice fall becomes an elevated hazard. Give cornice edges a wide berth, and when traveling on ridges, always stay on the windward side where signs of terra firma exist - a tree, a rock, - something to let you know you are not dangling in space and tempting fate. 

Régions couvertes