Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

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

If snow is wet and unsupportable on Thursday you could encounter wet snow avalanches on steep slopes. Rollerballs running down a slope are good indicators that avalanches could follow, and if you are sinking deep into the snow, shift your travels to lower-angle terrain or firmer snow surfaces.

Avalanche problems

  • Loose Wet

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

    Snow surfaces on all aspects got wet on Wednesday. In neighboring zones rollerballs came down, and some small wet loose avalanches were reported. Prolonged warm temperatures will continue on Thursday. If skies are cloudy, expect this problem to exist on all aspects. Clearing skies will probably limit avalanches to the southerly half of the compass. 

    Pay attention to how soft snow surfaces get. Search for obvious signs of weak surfaces such as rollerballs or recent wet loose avalanches. If you’re sinking several inches down, or noticing snow already sliding down, avoid steep slopes and terrain beneath those slopes.

    Rollerballs are great indicators that a wet loose avalanche could follow.  Photo: Andrew Kiefer

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1.5–2.5

    Danger remains on Moderate at upper elevations because of our ongoing concern for persistent slab avalanches. On Monday I traveled to 5000ft on the Mountain Loop Highway and found the persistent weak layer at the top of the thick Late January Crust, just over a foot down. A large avalanche occurred in the Baker backcountry on Tuesday, reminding us this layer is still present. The following is what we know about avalanches on the persistent weak layer:

    • The snowpack structure is inherently weak.
    • The layers are still reactive above 5000’ on aspects that did not receive strong sun in late January.
    • Reported natural and human triggered avalanches occurred at the same aspects and elevations.
    • They mostly occurred where there are 2 or more feet of new snow over the crust-facet layering.
    • Snowpack tests produce inconsistent results at the crust-facet layering, sometimes even in the same snowpit.
    • Many steep slopes - some very near avalanches that released in the same layers - have been ridden and skied with no results.

    The conclusion so far is that there are very few places where you could trigger one of these avalanches, but it would also not be surprising if another one occurred. If you venture onto steep terrain in these areas you are assuming a bit more risk than if the layering was not present.

Avalanche Discussion

A freezing level of 10,000ft thursday, with warm temperatures Wednesday and not much of an overnight freeze is a good indicator that snow layers are getting wetter and losing strength. Cornices could begin failing any day now. If one fails, they might be a good trigger for a persistent slab avalanche if they're in the perfect location. Keep an eye on terrain your traveling beneath, and consider giving large cornices a wide berth.

Regions covered