Bulletin d’avalanche

Northern Wallowas

Wallowa Avalanche Center
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Danger d’avalanche

Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 2 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Recent natural avalanche activity in the alpine combined with a reactive weak layer buried 2' or more, on mostly NW-N-NE aspects near treeline and above, makes human-triggered avalanches likely. Avoid steep wind-loaded and unsupported slopes in the alpine and near treeline avoid slopes >35 degrees with convex rollovers and/or shallow rocky areas where triggering a persistent weak layer is more likely to happen. 

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 La Grande Sno-Drifters Snowmobile Club.

Problèmes avalancheux

  • Persistent Slabs

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

    A pesky and persistent layer of buried surface hoar lurks in isolated pockets on mid-elevation NW-N-NE aspects. 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 yesteday from Sentinel Peak area, indicates a large and destructive natural avalanche cycle occurred in the last few days.  Recreationists should be very leary of travelling 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 awakend 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 degree) 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. 

    Propagating results were observed in Extended Column Tests on this layer on Saturday (3/2) 50cm down, on Sunday (3/3) buried surface hoar mixed with graupel was found sitting on top of the 2/26 crust at 7500' on a NE facing slope in the Northern Wallowas down 80cm. This layer failed down 60cm or 2' in a Compression Test and propagated in an Extended Column Test at 7600' on a NNW aspect in the Northern Elkhorns yesterday, 3/7. 

     

    (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

  • Wind Slabs

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

    Isolated pockets of reactive wind slab several feet thick may still exist near and below ridgeline at upper elevations on NW-N-E aspects. The effects of recent wind-loading may present as smooth hard pillows lurking below ridgelines or sub-ridges mid-slope, as cornices hanging imposingly over steep slopes, or if settled powder snow gives way to stiff punchy windboard. These are all the signs of potential wind slab. The lack of significant new snow or wind are helping the wind slabs stabilize. However, danger may lurk in isolated pockets. Look for and avoid steep slopes (>35 degrees) with large overhanging cornices, smooth textured wind pillows, and/or deposition zones with convex rollovers.  We may have a dangerous brew of buried surface hoar existing underneath stubborn wind slabs. Be leary of steep terrain below ridgelines that may be a bit more protected, but still accumulated drifting snow. The surface hoar may be lurking well into the alpine. 

     

    (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 Mountians 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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There is a slight chance that the fair amount of light density snow present could become moist with daytime warming, loose cohesion, and move down steep south-faciing  slopes > 35 degrees as wet loose avalanches at lower elevations. Wet loose avalanches or sluffs can carry you to places you don't want to be. Look for rollerballs and pinwheels as visual clues of wet loose avalanches. If you see these signs or start sinking into the wet snow seek lower-angle slopes or slopes without terrain traps in case you take a ride. 

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 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 your not dangling in space and tempting fate. 

For future reference: Relatively calm conditions for several days combined with clear cold nights have produced surface hoar crystals on W-N-E aspects well up into the alpine. When we start to get significant snow again this buried layer of surface hoar could become an avalanche problem. When out touring today pay attention to where you are seeing significant surface hoar formation and tuck that little tidbit in your memory bank for future retrieval. 

 

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