Boletín de aludes

Elkhorns

Wallowa Avalanche Center
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Peligro de aludes

Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Wind-drifted snow will form sensitive slabs that should be avoided on or around slopes >30 degrees, including runout zones.  Signs of wind-affected snow include dune-like formations, drifts, plumes, and cornice growth.  With known weak snow layers buried 2' or more below the surface triggering a wind slab could produce a much larger and unsurvivable avalanche.  

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

This forecast is sponsored by CB Construction.    

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    Winds will continue today, primarily from the South-Southwest.  With plenty of snow available for transport and more in the forecast today you should expect wind-drifted snow to accumulate and form into a sensitive slab.   The most common signs visual signs of wind-stiffened snow are dune-like formations, drifts, cornice growth, and plumes.  Near ridgelines, you may notice the snow has been removed, frequently down to an old crust layer, and re-deposited onto another slope.  If you suspect a slope has been wind-loaded it's best to avoid the slope, including traveling in the runout zone of slopes greater than 30 degrees.    

    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

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2.5

    Weak snow including buried surface hoar and facets above a crust have become reactive over the past several days.  The layer of surface hoar buried on 2/26 has been found in the Elkhorns, Southern Wallowas and Northern Wallowas. It should be noted that in the Northern Wallowas, a report from Sentinel Peak area, indicates a large and destructive natural avalanche cycle occurred in the last few days.  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...this has been a sleeping dragon, but as the loose storm snow has consolidated and become a slab, this has awakened the dragon. In most zones, this surface hoar layer is buried about 2' deep. 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. 

    (3/7/2024)

    Pete's Point

    NE face of Sentinel Peak. Aprox 9300’ for the crowns, 7800 for the toe. Appears to have happened within the last day or two. No noticeable new snow or wind transport on the debris or bed surface. Appeared to be triggered naturally. Multople crowns, multiple layers. Aprox. 2’ to 6’+. Over 2000’ wide.

    Photo: Brandon

    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.

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Persistent Slab Problem:  

What:  Weak snow layers in the forms of facets and surface hoar buried during February have awoken and become reactive over the past week.  The 2/1 buried facets sitting atop a stout crust was the known weak layer that caused the avalanche on Gunsight Mountain on March 6.  There have been other 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 Valentines, 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.  

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. 

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