Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

You may be able to trigger avalanches in areas where the winds have built drifts of snow. Identify slopes with stiff snow over soft layers using your probe or ski pole. If you experience warning signs like loud collapses or cracks shooting in the snow move to low-angle slopes or wind-sheltered terrain.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    More south wind could transport snow in the early morning of Thursday.  This will add slabs to those that built from westerly winds earlier in the week. There is potential for these wind slabs to step down to deeper weak layers, creating large and dangerous avalanches.

    Watch for actively blowing snow. Surface texture can also help you identify wind-affected terrain. A rippled surface indicates that the winds have been drifting snow into slabs. Look for signs of blowing and drifting snow and use small hand pits to identify stronger layers of wind-driven snow over soft powder snow. Cracks shooting out from your skis, snowboard, or equipment and loud whumphing collapses are a sign that steep slopes could avalanche. 

    (12/7/2022)

    Top loaded lee feature in Owl Creek. This slope would be suspect for triggering a wind slab avalanche

    Photo: Matt Primomo

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    It's been a week since the last significant storm, and red flag observations of collapsing and cracking are decreasing. Even without these loud warning signs, it's important to dig down and identify any weak, sugary layers in the snowpack lingering below last week's storm snow. In areas where you find this weak snowpack structure, it is important to continue to make conservative terrain choices and use lower-angle routes. We suspect areas near Mission Ridge and Blewett Pass have elevated danger associated with this problem. 

    While these layers may be beginning to heal, it is a slow process, and there is still the possibility of triggering a large and dangerous avalanche that runs at or near the ground. Northern aspects above 5000ft, particularly locations where the wind has drifted snow, are the most likely places to trigger these avalanches.

    (12/7/2022)

    A sled triggered avalanche on a road cut. On a larger feature, a bigger avalanche could have resulted. N at 6,200ft in Owl Creek.

    Photo: Matt Primomo

Avalanche Discussion

While access to higher elevations has improved significantly, it still requires lengthy approaches with many trees, shrubs, and stumps to avoid. Therefore, we are just beginning to understand the distribution and reactivity of these weak layers surrounding the 11/22 and 11/25 crusts throughout the zone, and we still have quite a lot of uncertainty. Evidence continues to roll in as avalanche professionals, and winter recreationists report finding this snowpack structure in many locations. However, some areas don't have enough snow overlaying this weak layer to produce avalanches. Therefore, conservative terrain choices are warranted until we gain more information. We have yet to put this layer to the test with another big storm, but snow is in the forecast, and the next storm event may give us additional information on how sensitive this layer is to triggering. 

If you are out and about in the mountains, you can help us by submitting an observation. 

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