Boletín de aludes

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Wallowa Avalanche Center
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Peligro de aludes

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

Lo esencial

New snow in the forecast, plenty of snow available for transport, and forecasted winds strong enough to transport snow from one place to another means we should see more windslab formation especially  above treeline and at ridgelines on north, northeast, and east facing terrain. Cautious route finding and conservative decision making will be essential for those who choose to recreate on steep leeward terrain in the alpine today. It is advised that recreationalists avoid windloaded terrain steeper than 35 degrees today, particularly in the alpine.

 

   This forecast is sponsored by onX Backcountry 

Problemas de aludes

  • Wind Slabs

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

    Yesterday while ski touring in the Northern Elkhorns I observed 4"-6" of new snow that fell Thursday into Friday. Weather stations throughout our forecast region were showing similar snow totals as well. Forecasted south winds and new snow  today coupled with plenty of fresh snow available for transport should create fresh windslab formation at and above treeline and especially near ridgelines on leeward north, northeast, and east facing terrain during the day today, throughout the region.  Yesterday on an east facing terrain feature at around 8500' just leeward of cornices, I was able to easily trigger shooting cracks as I traversed the wind loaded area under the cornices. Had the terrain been a sustained 35 degrees or steeper, the result would have been a windslab avalanche. More south wind and new snow in the forecast today will increase the snow load on existing windslabs,  increasing the likelihood for a human triggered avalanche on steep windloaded terrain, particularly near ridgelines. Assess conditions carefully today if you are considering traveling through or recreating upon steep slopes especially in the alpine and near ridgelines. 🚩Windslabs have a smooth, rounded, pillow like shape and can be found on the leeward side of ridges and ribs. 🚩Wind transported snow has a dense feel to it.🚩 If the slab is dense or firm enough to support the weight of a human, it can sound hollow or drumlike while traveling across it. 🚩Shooting cracks projecting out in front of skis or boards while traveling through windloaded terrain is a bulls eye red flag that the snow you are moving through is unstable and could avalanche. If we start observing any of these red flags or, especially  avalanches, in areas near or similar to the area we are traveling in,  it is time we consider recreating on lower angle slopes less than 30 degrees in steepness. Cautious route finding and conservative decision making will be essential today if you choose to travel in avalanche terrain in the alpine. If there is any doubt about the stability of a slope you are considering it is advised that the recreationalist should avoid the windloaded avalanche terrain in question.

    (3/3/2023)

    I observed shooting cracks yesterday when ski cutting under these cornices on an east facing slope at 8544' . Had the slopes in question been longer and greater than 35 degrees in steepness, I believe I would have triggered a windslab avalanche. 

    Photo: TG

Avalanche Discussion

Also while ski touring yesterday, I observed loose dry avalanche activity in a couple of steep, isolated pockets unaffected by wind. I doubt that will be a problem today but consider that when skiing terrain 35 degrees or steeper particularly below treeline where the snow will be less consolidated. In my travels this week in the Western Wallowas and Northern Elkhorns I have had the opportunity to dig plenty of snowpits. Although I am still seeing evidence of poor snowpack structure in the upper half of the snowpack, the crust facet combinations that I have been observing  are continuing to consolidate and gain strength. My snowpits yesterday in the Northern Elkhorns revealed a mostly right side up snowpack in the top 4.5' or so. I did see some rounding facets buried 18" or deeper but these faceted layers continue to round and gain strength. Stability tests revealed failures using a moderate amount of force in the top 1'-2' of new snow, above the PWL's . Shears were either resistant planar or progressive compression. No propagation was observed in stability tests yesterday and I did not observe buried surface hoar.

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