Lawinenlagebericht

Blues

Wallowa Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 2 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Poor snowpack structure and recent loading have created a persistent slab problem. Where a foot or more of cohesive snow (slab) exists above weak buried facets it is possible to trigger an avalanche large enough to bury a person. The only way to control your exposure to avalanches is to avoid terrain steeper than 30 degrees, including runout zones.  

This forecast is sponsored by Robert Brooks Painting in La Grande.  

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Just as anticipated, January's long high pressure weakened the upper snowpack and created several layers of incohesive facets that are now buried 1-2 feet thick across the forecast area. On southern aspects these weak grains exist beneath sun crusts. While evidence of this instability may be sparse, the poor structure of the snowpack is not to be trusted until either significantly loaded or given time to heal. Currently, February's storm snow is slowly settling into a cohesive slab, and reactivity may increase in the future - especially in areas where new loads are added. This will require patience, as the only way to truly avoid avalanche risk is to avoid avalanche terrain and recreate on slopes under 30 degrees. 

Avalanche Discussion

While the current persistent slab instability will demand patience, the relatively deep snowpack below the January 31st interface will contribute to a steady healing process. This process may be expedited if the snowpack continues to receive load, as gravity will pack faceted grains closer together where they can quickly bond. Some forecast areas have received more load than others, and thus revealed more instability. In the Southern Wallowas, forecasters have discovered buried surface hoar at the 1/31 interface, leading to propagation in snowpack tests in sheltered areas below treeline. In other areas there may not be enough of a slab to consistently yield results. This problem may also show itself in areas where wind has created a thicker, stiff slab above. With ample snow available for transport, small wind slabs may be present in leeward terrain, even when not specifically listed as an avalanche problem. 

What to do:  Persistent slab problems are notoriously difficult to manage due to a lack of feedback. You may not observe any signs of instability. Natural persistent slab avalanches are rare after the initial loading period. Slopes capable of avalanching may even already have tracks on them. Until the snowpack structure improves the only way to eliminate the risk of avalanches is to avoid terrain steeper than 30 degrees.   

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