Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

It's still possible to trigger a slab avalanche in wind-drifted snow.  Use lower-angled terrain to navigate around steep features where you identify signs of wind drifting or see pillowy-looking wind slabs. Cold temperatures persist with strong east winds in some parts of the zone. Be prepared to deal with an injury or gear failure where you can't rely on movement to keep you warm.

Avalanche problems

  • Wind Slabs

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

    Use the standard clues like cornices and wind-scoured surfaces to identify the wind-loading pattern around you.  Active loading will be observed in locations with higher wind speeds. Hand shears and test slopes on small, wind-drifted features can give you a sense of slab reactivity. Move cautiously if you head into more aggressive terrain. Even though there might be no wind-drifted snow where you enter a steeper slope, that doesn’t mean you won’t find it a short distance away.

    While slabs should be harder to trigger on Friday, they are still out there, especially on slopes approaching 40 degrees or on unsupported slopes. Locations farther east in the zone - or near major mountain valleys - will see strengthening winds and fresh slab formation by the afternoon as east winds grow stronger. Fresh slabs will be easy to trigger. You might even see a few natural avalanches as well.

    Touchy wind slabs were dense, chalky and looked a little like this.

    Photo: Simon Trautman

Avalanche Discussion

An NWAC Forecast team traveled north of Hwy 2 on Friday. They found about 3' of snow cover, mostly over bare ground or a shallow crust at 3000'. Most of that snow is estimated to have fallen in the last two storms. Minor wind transport was noted on mid-elevation ridgelines. Backcountry travelers triggered a  handful of small and one larger slab avalanche in West North. Also, very large natural avalanches - that likely released with wind loading overnight - were observed on the west and south aspects of Goat Mountain and also high on the southwest side of Shuksan.  In the Passes, stable snow was the main theme with instability limited to loose dry avalanches and small, soft slabs.

White Chuck saw an additional 6" of new snow Thursday evening and recorded a low temperature of -9F Friday morning. The Hart's Pass Snotel (northwest of Mazama in East North) saw a low temperature of  -31F. Brrrrr . . . . . Despite the cold temperatures, full sun on Saturday will slightly warm sheltered solar aspects. Keep an eye out for signs of instability related to warming.

While recent wind slabs are the type of avalanche you are most likely to encounter,  there is a low chance you could trigger a very large slab avalanche no matter if a slope is wind-loaded or not. A layer of facets overlying the 12/30 melt-freeze crust is now buried 3-5’ deep in many locations. Avalanche activity associated with this interface is decreasing, but recent control work pulled out a slab avalanche 3-5’ deep. There is also the possibility that larger natural avalanches observed Friday are related to the 12/30 as well.

Use caution approaching big slopes in the coming days and get a handle on snowpack structure and recent avalanche activity before considering more complex terrain. As usual with lingering persistent weakness, the likelihood of triggering is low. If you were to trigger one it would be with a very large load or in very steep, unsupported terrain.

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