Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

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

Another round of wind slab is in store for Sunday. Avoid travel on steep terrain features where you observe smooth drifts of wind transported snow. This will reduce the risk of triggering an avalanche until the new slabs have time to bond to the layer below. Sun breaks could produce rollerballs and loose wet avalanches - move away from steep slopes in the sun where you observe either.

Avalanche problems

  • Wind Slabs

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

    Fresh slabs of newly wind drifted snow should be the primary factor in your tour plan for tomorrow. Strong winds and 6” of new snow by the end of Saturday were reported as beginning to build new slabs. Stormy conditions will taper overnight but wind slabs will remain in play on Sunday. If you find more snow than expected then assume a higher level of danger.

    Pay attention to the pattern of wind loading by using scoured snow surfaces, cornice-like features, and changes in snow texture to figure out where wind slabs lurk. Stiff, smooth snow surrounded by rougher surfaces is probably wind slab. Upside-down snow is also a great sign that you have found a wind slab, but also a sign of less great riding and skiing conditions.

    You can use test slopes and other tools to evaluate wind slab bonds to the layer below - or just steer around steep wind loaded terrain.

     

    (1/19/2023)

    A recent wind slab avalanche. Wind slabs are more likely to be found in steep terrain below cornices.

    Photo: Robert Hahn

Avalanche Discussion

While most of the west slopes should remain cloudy tomorrow, we may see some sun breaks in West North. Widespread wet loose activity is not expected but as usual, keep an eye on terrain overhead that is warming in the sun and producing rollers or very small loose wet avalanches.

A weak snow surface of light-density new snow, surface hoar, and facets was observed the past few days. Observations Saturday point toward these surfaces being warmed up and then destroyed by the wind prior to new snowfall. In areas where weak snow survives and is buried intact, you could find new slabs that are easier to trigger or release in surprising ways. Identify and investigate the interface between new and older layers and ease into steeper terrain by starting with smaller, less consequential slopes.

Observers Saturday found a big change in conditions from Friday with strong winds, wind drifted snow, poor visibility, highly variable and temperature-thickened snow surfaces, and an overall decrease in snow conditions from the days prior. 

The last storm on Jan 17-18th brought 8-16” of new snow to West North. Near treeline, there is 1-2’ of snow above the stout MLK rain crust with 3’ or more in wind loaded areas. Upper snowpack layering is generally right side up with wind slab layers bonding and becoming unreactive. 

Avalanche activity related to the latest storm:

Jan 18th - a large natural avalanche was visible as the storm petered out (last gallery photo)

Jan 19th - human triggered wind slabs to D2, obs of another natural, probably from the 18th

Jan 20th - one snowmobile triggered wind slab, small rider triggered wind slab, wet loose cycle to D2 on SE>SW aspects 

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