Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

Triggering an avalanche large enough to kill you is likely on many slopes. To reduce the chance of triggering one of these, continue giving slopes greater than 30 degrees a wide buffer, especially in wind-drifted areas. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    Weak, faceted grains lurk 2-4 ft below the snow's surface. This weak snow was the culprit of the recent fatal avalanche on Darland Mountain and numerous other avalanches across the region. Observers continue to report obvious signs of instability, such as whumphing collapses and propagating test results on the Early February Crust.

    This serious weak layer of concern requires patience and strict management. These slabs can trigger in surprising ways. You can trigger them from flat or low-angle terrain long distances away from steep slopes, and they can break far above you. Before triggering an avalanche of this type, you may or may not receive any direct signs of instability. Therefore, your best strategy to avoid triggering a large, unsurvivable avalanche will be to avoid travel on or below slopes greater than 30 degrees. 

    (3/1/2024)

    You can trigger similar avalanches on Tuesday

    This remotely triggered avalanche occurred on a North aspect at 6300 ft near Darland Mtn on Friday, March 1st.

  • Wind Slabs

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

    These wind slabs are likely gaining strength with time, but with poor structure across the region, you shouldn't ignore textured drifts and blowing snow. Days of loading wind speeds formed slabs, drifts, and cornices near upper-elevation ridgelines and in some middle-elevation terrain. Look for variations in snow appearance, texture, and stiffness to determine which slopes are most likely to hold a wind slab. They'll often form under cornices, beneath rock and cliff bands, and near the break-over of chutes and unsupported features. Chances are, these slabs rest above persistent weak layers mentioned above. So, any triggered slab could grow very large and wrap around terrain features. If you see blowing snow, textured drifts and feel stiffer snow under your feet or sled - it's time to steer clear of avalanche terrain. 

    We're just coming out of a windy period so look for blowing snow and textured surfaces to help you identify wind-loaded aspects. 

    Photo: Katie Warren

Avalanche Discussion

Tuesday is shaping up to be a pleasant day in the mountains. The forecast is calling for some sunshine, so look for wet surface snow to possibly form on steep, sunny slopes. The cold temperatures and partly cloudy skies should help keep wet loose avalanches at bay, but you cant rule out an occasional one on steep south aspects. Rollerballs and pinwheels are great indicators that tell you that wet loose avalanches could soon follow. These should remain small. 

Observers across much of the Washington Cascades, particularly the eastern slopes and the west-south, have reported numerous large avalanches failing on old snow 2-4 ft below the surface. In addition to the fatal avalanche accident on Darland Mt on March 1st, another large avalanche on an adjacent slope was remotely triggered by a group of snowmobilers. This widely propagating avalanche occurred on a north aspect at 6300 ft. You can check out the observation here. NWAC forecasters visiting the accident site also reported this separate large avalanche (avalanche observation). These all likely failed on the Early February Crust. 

This pattern of persistent slab problems can be incredibly challenging for backcountry decision-making. It takes extremely conservative terrain management and patience. This winter's lower-than-average snowfall and warmer-than-average temperatures contribute to a shallow snowpack prone to developing these tricky weak layers. The issue is especially apparent in the eastern Cascades, which, on a typical year, is already a bit shallower and weaker than areas west of the crest. So, if you're venturing into these eastern zones this winter, be prepared to take a step back in your typical terrain selection and understanding of the snowpack. It's easy to be surprised in these conditions, so with the increased complexity of the snowpack, choose low-angle terrain to enjoy the fresh snow. 

 

Your avalanche, snowpack, or weather observations are extremely valuable to the avalanche community. Help create a more accurate avalanche forecast by submitting your observations here. 

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