Lawinenlagebericht

West Slopes South

Northwest Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

Uncertainty surrounding the potential of triggering a large avalanche on buried weak snow should have you traveling cautiously in the mountains on Tuesday. Take the time to dig in the snow and look for this weak layer before you commit to a slope. You may even still be able to find a lingering Wind Slab or trigger some loose snow if you venture to high elevation or extreme terrain. 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1.5–2.5

    Persistent slabs are a tricky avalanche problem to deal with. You could be out in the mountains all day and not see any signs of instability and then all of a sudden find the sweet spot where you trigger a large and potentially deadly avalanche. These avalanches can fail in surprising ways by spanning far distances, breaking above you, or wrapping around and connecting terrain features. Your best mitigation tool is to choose lower-angled terrain where you’re less likely to trigger one of these beasts.

Avalanche Discussion

After a weekend full of somewhat unusual avalanche reports from throughout the zone, avalanche professionals dropped some more in our inboxes on Monday. At White Pass, the 12/8 buried surface hoar was found on all aspects and at all elevations. This layer failed in every test thrown its way, including showing a propensity to propagate during extended column tests. Over near Crystal, we received word of yet another deep avalanche, this time in Goat Lake Basin. The slide is suspected to have failed during the storm on the 11/22 facet/crust combo. Down in the neighboring Mt. Hood zone, multiple avalanches have been reported on the 12/8 facets, some of which have been triggered remotely or partially buried individuals. 

These red flag signs of instability from throughout the zone and beyond should immediately grab your attention and make you start to think about what could be going on in the terrain where you like to recreate. Be prepared to take a look at the 12/8 interface wherever you are and see how it is reacting. You should be able to find it anywhere from 1-2 feet below the surface. Even if you’re not seeing it pop cleanly with shiny feather-like grains, you could find that it is still failing and taking longer to heal a typical Pacific Northwest storm interface. 

While not unprecedented, this has been an unusual start to the season which has led to some unusual early-season challenges. The generally cold temperatures, amount of snow, and to be frank, lack of rain, have given us good early-season coverage, but perhaps a less-than-ideal snowpack structure. Persistent Slab problems are tricky. Tricky to manage, tricky to forecast, and tricky to put to bed. You should be traveling cautiously in terrain and doing your homework before committing yourself to a slope. Think about traveling as if conditions are Considerable, not Moderate, even though the likelihood of triggering one of these slides is lower. In fact, you could be out all day and not see a single sign of instability. You will likely have to dig in order to find out what potential issues lurk beneath the surface.  

And of course, just because we’re hammering home the persistent issue at hand doesn’t mean there aren’t other hazards you could run into out in the mountains on Tuesday. If you venture to the highest peaks or more extreme terrain, you may still be able to find some lingering storm instabilities in the way of Wind Slabs or loose avalanches. Maybe the sunshine will help some snow shed from trees and rocks, grabbing a bit of snow as they descend steeper slopes below. At lower elevations, you may still need to manage some early-season hazards such as creeks, holes, or small trees and bushes.

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