Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

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

Unstable slabs of wind drifted new snow may be found above treeline. You could trigger a small avalanche in areas where you observe dense slabs poorly bonded to sugary snow or firm crusts below. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Gusty south and west winds will continue to be the main ingredient in avalanche danger. The size and distribution of new wind slabs could vary greatly.  It depends on how much loose snow is available for transport on windward slopes plus fresh snow to add to the mix. Some slopes could have no new wind slabs while they might be readily found on others. Though mostly small in size, wind slabs can be plenty dangerous if there are consequential terrain features like trees, rocks, gullies, or cliffs in the track or run out.

    The current crop of wind slabs can be identified as stiff, smooth-looking drifts that might be surrounded by scoured or otherwise wind affected snow surfaces. You could find these just below ridgeline and also farther downslope on cross-loaded features. Poor visibility or a thin coat of new snow could make wind slabs harder to pick out in the terrain around you. Use simple tests like hand shears and test slopes to see how well these slabs are bonded to layers below - or simply bypass steep wind loaded features on lower angle, planar terrain.

    Example of shallow wind slab avalanche from February in West North 

    Photo: NWAC Public Obs

Avalanche Discussion

With precipitation focusing to the north and then to the south, West Central will probably see less precipitation than any other west side zone over the next few days.  You may encounter signs of instability like rollerballs and pinwheels with a quick rise in snow levels and maybe even some sun breaks later on Saturday.

Though signs of avalanche activity can be found throughout the mountains, most observations were of the large slab and wet avalanches from the last major storm over a week ago. Recently triggered avalanches were limited to small and shallow wind slabs in alpine terrain (March 5th, March 9th).

Any new snow will fall on a variety of surface layers including sun crust, dry and weak snow in shady, wind sheltered terrain, old wind slabs, and wind scoured or otherwise wind affected surfaces. Weak, faceted snow continues to be found around the Cascades at or near the current snow surface, sometimes above crust layers from the most recent atmospheric river event in early March. Other the snow surface and new wind slab layers, the upper snowpack is generally strong with no current layers of concern. Human triggered avalanches on the Valentine’s Day crust and the late January crust-facet layers continue to be an issue in adjacent regions (East North and the South Coast and Sea-to-Sky zones in Canada). There were no reported avalanches in West North or Central associated with deeper layers since the natural avalanche cycle in late February/early March.

 

Regions covered