Bollettino valanghe

Elkhorns

Wallowa Avalanche Center
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Pericolo valanghe

Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
Senza grado
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

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: CB Const Inc.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    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.

     

    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 the past several days have consolidated the upper snowpack. Below-freezing temperatures today should lock up the surface snow. The warm temperatures and sunshine have melted more low-elevation snow and exposed more objects in the higher-elevation terrain. These changes to the surface snow have not affected the snowpack below. Facets and Depth Hoar are still present sandwiched between melt-freeze crusts and at the ground. You can see observations that showcase the Persistent Slab avalanche problem in the Elkhorns, Southern Wallowas, and Northern Wallowas. At this time, it is best to avoid avalanche terrain (slopes greater than 30 degrees).

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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