Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Steep slopes with more than about 6 inches of the storm snow layer are likely to avalanche with a human trigger on Saturday. Most snow will fall with peak winds overnight, and avalanche activity is expected to be highest in the morning, although weather forecasts vary and danger may be higher or lower depending on our actual snowfall amounts. Steer around steep slopes while the snowpack settles, especially in areas with thicker, wind affected deposits where snow will be more reactive and resulting avalanches could be larger. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    With Considerable danger, signs of avalanches or weakness in the snow may not be as obvious as with High danger, however chances of triggering an avalanche are still likely- it may just be tougher to find the clues telling you not to head out on a slope.  The majority of snowfall is expected in the early hours of the night, and  it's likely that you'll be able to trigger reactive storm slabs, especially at the start of the day Saturday. Locations with more than 6 inches of snow over the old snow layer, which is a crust in most spots, are where you can expect to trigger a storm slab avalanche. The underlying crust may provide a good sliding layer, producing faster and longer-running avalanches. 

    Moderate to strong winds, which have since backed off, occurred while the majority of snow fell. Locations with thicker, wind drifted pockets are where you can expect it to be easier to trigger an avalanche, and the avalanche will probably be larger. New drifts may be subtly hidden beneath non wind-affected snow. 

    With a relatively shallow layer of new storm snow over an abrupt transition to the underlying crust, you can assess the new snow layer to see how reactive it is. Small hand pits to investigate the bond are applicable in this situation if you know how to do them. Checking small test slopes on skis or boards, snowshoes, or snowmobile works well also. In general, stay off slopes steeper than 35°. If you experience long, shooting cracks from your feet or sled, recent avalanches, or experience any other signs of instability, dial it back even more.  At lower elevations, avalanche danger is Moderate, which means avalanches are still possible but we expect the layer to settle quicker and bond a little better to the underlying layer. 

    A small avalanche which was skier triggered on a test slope in the Heather Meadows area. 

    Photo: Pete Durr - USFS Backcountry Ranger

Avalanche Discussion

Check out THIS observation from Bagley Basin on Friday, to get an idea what snow was like before the new snow began falling. We're entering a period of typical spring storms, with intense bursts of snowfall and wind. Around 6 inches of snow is expected to fall before midnight, but we'll continue to see bursts through the early morning hours and much of the day, which may total up to a foot by the end of the day.  If more or less snowfall occurs than forecasted, the avalanche danger may be higher or lower than this forecast. During any periods of intense snowfall avalanche danger could peak. 

Some pockets of soft snow beneath the new snow layer  were still hanging on in mid-elevation terrain in areas both shaded and protected from the wind. Avalanches on Saturday should be mostly restricted to the old/new snow interface or within new snow layers. We could always see bigger avalanches triggered by large loads or on a few slopes holding buried layers of surface hoar, near surface facets, or near crust facets.

Sun breaks are possible, and small wet loose avalanches could run if steep slopes moisten enough. The new low density snow could also run as a dry sluff on steep slopes as well. Please submit an observation if you get out on Saturday, as it'll help us provide a better forecast for you!

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