Boletín de aludes

Elkhorns

Wallowa Avalanche Center
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Peligro de aludes

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

Lo esencial

Weak sugary snow at the bottom of the snowpack makes it possible to trigger an avalanche breaking near the ground. Anywhere there is sufficient snow to get you off the ground you can find this avalanche problem. To avoid triggering these avalanches stick to terrain less than 30 degrees.

This forecast is sponsored by: Anthony Lakes Mountain Resort.

Problemas de aludes

  • Persistent Slabs

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

    Snow that fell in the late fall and early winter has turned into weak sugary snow. On top of this weak snow, there are several layers of more dense snow and some very dense crusts. Around some of these dense crusts, thin layers of weak snow have developed.  This snowpack structure creates a Persistent Slab avalanche problem. Persistent Slabs are just as they sound: slab avalanches with danger that persists due to the weak snowpack structure. These avalanches are difficult to predict and often give no warning signs. The best way to not get caught in an avalanche is to avoid the terrain they exist in.

    Warm temperatures have affected most of the preserved cold snow. Before it refreezes there is a chance you could encounter some wet snow avalanche problems. Look for rollerballs and pinwheels for signs these wet snow conditions exist.

    No avalanche danger rating has been applied to the below treeline band due to the lack of sufficient snow cover at that elevation.

     

Avalanche Discussion

New: Warm temperatures on 12-28/29 have affected the upper snowpack. Rollerballs and pinwheels were observed on East and South facing terrain. A thin warm-up crust was observed up to 8800' even on north aspects. The warm temperatures have not done anything to change the lower snowpack. Facets and Depth Hoar were found yesterday in the Southern Wallowas and Northern Wallowas. This same weak layer was also found on the 28th in the Elkhorns (Thanks to WAC Motorized Ambassador- Kevin Cassidy, for putting his skis on and submitting that observation!).

State of the snowpack: Small amounts of snow that fell during our prolonged autumn have rotted and weakened. On top of this several rain storms or periods of above-freezing temperatures have created crusts. Snow depths range from nothing in the below treeline zone to 90cm/3ft in the above treeline terrain. While the upper portion of the snowpack feels sturdy, there are thin layers of weak snow around the melt-freeze and rain crusts and the base of the snowpack contains a combination of well-developed facets mixed with rounded grains. This snowpack structure creates a Persistent Slab avalanche problem.

The Persistent Slab avalanche problem is a tricky one. You can't see it by visually scanning the mountains. It isn't obvious on the surface of the snow. Other clues like cracking, collapsing, and whumpfing may not occur. Even if you dig down and conduct stability tests the results can be hard to interpret and inconclusive. This is the dreaded low likelihood, high consequence scenario. You might not trigger one of these avalanches or even know it is there, but if you do, it will break near the ground and take all the dense snow on top of it with it.

The best way to avoid getting caught in one of these slides is to avoid where they exist. That means anywhere snow has stuck around since fall, has more snow on top of it, and is steeper than 30 degrees. Given the shallow snowpack everywhere, colliding with obstacles would make taking a ride in an avalanche particularly nasty. Many rocks, trees, stumps, and down timber are on the surface or very shallowly buried.

If you get out to slide or ride please send us your observations! A picture or quick description of the conditions you encountered is SO helpful in creating these avalanche forecasts for you.

 

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