Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 2 years ago.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

Highlights

A fast-moving, windy storm will sweep through the region on Friday. Anticipate a sharp rise in avalanche danger as heavy snowfall and strong winds turn on. Find sheltered, lower-angle terrain as conditions deteriorate. Convergence zone enhanced precipitation could sustain snowfall through the end of the day.

Avalanche problems

  • Storm Slabs

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

    Precipitation and snowfall amounts for the coming storm are not exceptional, but a few factors up the ante. You could see snowfall rates of over 1” per hour. Fresh slabs are more reactive when this much snow comes down this quickly. Strong winds are forecast to increase throughout the day and build thicker, more sensitive slabs on leeward aspects.

    Finally, the new snow will fall on a variety of surfaces including crust, wet snow, old dry snow, and in the worst-case scenario, a thin layer of faceted snow or surface hoar overlying crust. The old snow surface out there has lots of variation. This is a good setup to see more reactivity at the old-new snow interface than usual.

    Stormy conditions should keep you off big open slopes. You can use simple tests like hand shears, test slopes, and tilt tests to evaluate the bond of new snow layers. Whatever you find, the best bet would be to stick to low-angle, sheltered terrain while the storm plays out.

    Very small test slopes are great indicators of instability on bigger ones where you could actually get caught in an avalanche.

Avalanche Discussion

Reports of crusty conditions and challenging travel seem to have kept folks out of the mountains and limited observations over the past few days. Or maybe they found the pow and didn't want to share. Who knows.

Either way, the story is the same across much of the west side of the Cascades. Slab and wet avalanche instabilities from last weekend have mostly resolved. Observed avalanche activity consisted of a few wet avalanches, most of which initiated in rocky terrain at mid and upper elevations. No slab avalanches that released within layers of dry snow were reported other than those that occurred over the weekend.

A crust now tops the snowpack pretty much everywhere. It is found on most aspects and low and mid elevations, and slopes facing the sun at upper elevations. A trace to a few inches of new snow didn’t do much to improve riding conditions but may have faceted and become weak. Surface hoar was also reported.  The wide variety of surface conditions means there could be a wide variety of avalanche activity, even between slopes with similar characteristics. Take the time to assess the bond of the old-new snow interface through the weekend before steeping into steeper terrain.

Regions covered