Bulletin d’avalanche

Blues

Wallowa Avalanche Center
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Danger d’avalanche

Fri
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

You are most likely to trigger a Dry Loose Avalanche in steep terrain >35 degrees.  New snow sitting above a melt-freeze crust has the potential to move rapidly downhill in steep terrain.  Before committing to large terrain features determine how well the new snow is bonding to the old snow surfaces. 

It remains possible that you could trigger a large persistent slab avalanche in terrain >35 degrees near the treeline.  

This forecast is sponsored by Eagle Cap Mountain Guides.  

Problèmes avalancheux

  • Loose Dry

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

    The new snow (light density), sitting on a crust from Sunday-Mondays warmup will likely move in steep terrain >35 degrees.  These Dry Loose avalanches may not be big enough to bury you but could push you into consequential terrain.  If you suspect there is a possibility of triggering a dry loose avalanche, avoid riding in terrain with hazardous runout zones, such as terrain traps, rocks, trees etc.  

    Dry Loose Avalanche: An avalanche that releases from a single point and entrains cohesionless snow as it fans downhill.

  • Persistent Slabs

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

    Yesterday while traveling in the Blues I found two different persistent slab problems around 5,300' on a Northwest and East Aspect.  On a NW aspect, I found a layer of buried surface hoar down 8", which was reactive in my extended column test.  In my second pit (see photo) I had full propagation in my extended column test on a layer of weak facets sitting on top of the Christmas crust down 2'.  

    These layers are concerning, due to the full propagation I observed in my snowpack tests.  Although I didn't experience any significant shooting cracks, collapsing or whumping these layers can "persist" for a long time, just waiting for the unsuspecting trigger to produce a large avalanche.  

    Before committing to terrain >35 degrees you need to dig down and look for weak snow with a slab above it.  If that's above your level of understanding it's best to stick to well-supported lower-angle terrain.  

    (2/22/2023) Photo: VM

Avalanche Discussion

Don't be surprised if you find isolated wind slabs above treeline today, with sporadic winds blowing from a multitude of directions in the past 24 hours.  Weather stations haven't indicated significant winds, but they shouldn't be ruled out especially if you observe dune-like formations, pillows, or see shooting cracks from your machine, skis or boards.  

It's always recommended to pay attention to the terrain above you, especially when complex terrain and significant alpine slopes are above you.  Consider the risk of triggering even a small dry loose avalanche and where you could end up if you triggered a small "sluff".  

While the chances remain possible forecasters and are still finding poor snowpack structure in isolated locations near the treeline.  Persistent weak layers can produce large avalanches and we are still finding buried surface hoar and facets around a crust in some of our snowpack tests.  You must dig down to determine the snowpack structure before committing to more challenging terrain.  Often times we don't observe Red Flags once these layers are more deeply buried, with a slab above them.  

 

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