Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Highlights

Shallow wind slabs may still be triggered on higher elevation, wind exposed slopes. Consider the potential for large cornice fall. Both of these problems can be found in alpine terrain, so look to identify and avoid areas of wind slab, and cornice hazard as you travel. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Observers triggered a small wind slab about 1ft deep on an easterly aspect above treeline near the Hairpin on Hwy 20 on Monday. These slabs may remain reactive through the day on Tuesday. Look for shooting cracks or firm, hollow-sounding snow as signs that you could trigger an avalanche on similar slopes. Steer around obvious wind features like textured or drifted snow, and wind pillows. Identify terrain such as steep and unsupported areas of slopes to avoid. Avoid steep slopes below cliff bands where spin drift may have formed thicker wind slabs. 

    If there are sun breaks during the day, keep an eye out for moist, sticky snow and rollerballs. These are all good indicators that wet loose slides could happen on steep slopes of similar aspects. Avoid terrain with increased consequences if you find loose snow runs downhill or entrains on steep slopes. 

    Textured snow surfaces like this can help you anticipate which slopes or features could harbor wind slabs. Photo: Ian Nicholson

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Cornices are sagging, and have been calving off somewhat regularly over the past 4 or 5 days. On Monday, an observer witnessed a large, natural cornice fall from alpine terrain in the Hairpin Valley above Hwy 20. With the recent natural activity, there's no reason to expect Tuesday will be any different. Plan your route to avoid spending time underneath areas where cornices are likely to exist, such as prominent ridgelines. If on a ridge, be sure to give cornices a wide berth, as they often break further back than one would expect.

    (3/6/2021) Large cornice blocking the entrance to a couloir off Silver Star peak. Cornices have been dropping over the past week or so.

Avalanche Discussion

On Monday, an observer triggered a small (D1) wind slab about 1ft deep on an east aspect at 7,300ft in the Hairpin Valley. They also witnessed a large cornice fall from a northwest aspect at 7,200ft. Several small, natural loose avalanches were found to have run and on Sunday, others found that loose avalanches were nearly big enough to push a skier around. 

The snowpack in the zone is generally deep and strong, without any layers of concern. Further east, the snowpack is more shallow, and could potentially harbor persistent weak layers. A widespread avalanche cycle occurred in the zone around February 22nd. Many avalanches were large or very large, and crowns encompassed many entire features. Avalanche debris from this event is still visible in many paths. 

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