Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

New snow and strong winds will increase the likelihood of getting caught in an avalanche.  Limit your exposure to avalanche terrain and stick with lower angled slopes to reduce risk. Don't let improving weather conditions in the afternoon lure you into steeper terrain - the new snow needs time to gain strength.

Avalanche problems

  • Storm Slabs

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

    You could trigger avalanches in steep, sheltered terrain on Wednesday. You are more likely to trigger one in wind loaded terrain where there are thicker, more reactive slabs. Natural avalanches could occur with intense wind loading or during periods of very heavy snowfall. This will be more the case in the morning before strong winds and snowfall abate.

    Stay in tune with the terrain around you and assess new snow layers as you travel. In all areas you can use simple observations like test slopes, hand shears and skin track tests to investigate new snow layering and the bond between layers. Also, monitor new snow depth in sheltered areas and use this as a reference in more wind exposed terrain. You are in areas that experienced wind loading if the snow suddenly seems deeper or if it feels stiffer underfoot. In general you can travel in simpler, less avalanche prone terrain to reduce uncertainty about avalanche conditions. 

    Many areas below treeline still don’t have enough snow to produce avalanches - but some slopes are starting to fatten up in that elevation band. Stay alert to steep terrain with smooth snow cover where you can now trigger avalanches.

    Example of a skier triggered avalanche (size D1) about 1 foot deep in recently fallen snow. 

    Photo: Stephen Semanski

     

Avalanche Discussion

Forecast precipitation amounts for the incoming storm are not record breaking, but below normal temperatures could produce much lighter, deeper snow than we normally experience. 1.25” of snow water equivalent (SWE) should easily produce 1.5 feet or more of new snow.

Conventional wisdom says such light density snow should not make much of a slab and that could be the case Wednesday. On the other hand subtle differences in temperature, precipitation intensity and wind speed (even in terrain not experiencing direct wind loading) could still produce a slabier layer over weaker snow. 

The 1' to 2' of most recent snowfall sits on a strong snowpack of rounded grains, melt forms and crusts. A big load from the approaching storm should be a good test  of a lingering weak layer - surface hoar and facets from November’s drought - that might still exist in colder and/or higher elevation terrain. 

Finally . . . don’t let deep new snow make you forget it's still early season out there and the snowpack is still shallow. Many hazards remain including exposed or barely buried trees and rocks, open creeks and other rugged terrain features.  

If you are out and about in the mountains, let us know what you find by submitting an observation.

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