Lawinenlagebericht

West Slopes North

Northwest Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Stay alert for slab avalanches failing in the new snow. Expect the most reactivity in mid to upper elevation wind affected areas, however avalanches may occur on other steep slopes as well. Stay off terrain steeper than 35 degrees, especially where you identify wind loading.

Lawinenprobleme

  • Storm Slabs

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

    Several natural and human triggered avalanches occurred on Saturday.  HERE and HERE are reports of skier triggered soft slab avalanches in the Iceberg Trees, failing in the storm snow on Saturday. Expect natural and human triggered avalanches to continue occurring on steep slopes on Sunday. You will find them most reactive in mid to upper elevation areas where there was wind loading . Avalanches could break within layers of new and wind drifted snow, or on variable old snow surfaces buried Thursday (3/18). Pay attention to the layer beneath the new snow, as melt freeze crusts were present before the storm on the southerly half, while direct northerly aspects above approximately 4500ft held dry snow. Weak snow may have formed at the surface of the dry snow during the high pressure over the last week, so failures may occur easily at that interface.

    Dig down to the new snow/old snow break to investigate how readily snow slides at the interface, or on layers within the new snow. Seek out small slopes before committing to consequential terrain. Avoid steep, unsupported slopes and start zones with signs of unstable snow, especially if it is wind drifted.

    (3/20/2021) A skier triggered storm slab avalanche occurred on a steep roll (35-40 degrees) in the Iceberg Trees on Saturday. The crown was 30-40cm deep, propagating 100+ft. D1. Photo: NWAC Observation

Avalanche Discussion

As of Saturday evening, 15 inches of snow was reported at the Heather Meadows weather station in the last 48 hours. Temperatures remained warmer than expected on Saturday and wet loose avalanches were seen in north facing terrain on previously dry snow by Mt Herman.  Temperatures are forecasted to cool overnight reducing wet loose avalanche potential. Until midday Sunday precipitation will slow and avalanche danger may decrease slightly. Snowfall and wind will increase in the afternoon, bringing the avalanche danger up again. Avalanche conditions may change significantly depending upon the time you’re out, and what aspect and elevation you are on. 

Keep cornices in mind as these already large features are continuing to grow. They could drop onto slopes below acting as huge triggers. Stand back from cornices along ridgelines and minimize overhead exposure to these features. Several large glide cracks and a few glide avalanches were observed recently as well. Cooling temperatures should limit glide activity for now, but these avalanches are difficult to predict. If you notice these crevasse-like cracks in the snowpack, avoid slopes beneath those features.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources.  Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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