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

It's possible to trigger a slab avalanche in wind drifted snow, especially in alpine terrain. Identify areas with recent wind loading and approach consequential slopes with caution. You may find wind slabs on south and west aspects where you do not normally see wind loading.

Avalanche problems

  • Wind Slabs

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

    A new crop of slabs built by northeast winds was observed in neighboring forecast zones. They were not necessarily widespread in distribution - some areas had extensive wind transport, others had none. On the other hand, they were reactive to the weight of a single person and large enough to injure and possibly bury someone. The latest wind slabs are now 24-48 hours old and becoming more difficult to trigger, but could still occur on convex slopes or other unsupported features. The likelihood is greatest in alpine terrain that saw the most wind transport. The few inches of snow and moderate winds forecast for Wednesday morning should not add much to the problem, but stronger winds and/or greater snowfall could further increase the danger near treeline.

    Pay attention to the pattern of wind loading as you gain elevation. Filled in tracks, scoured snow surfaces, cornice-like features, changes in snow texture - pay attention to these and other cues to pinpoint where wind slabs could lie in wait. Evaluate the bond of wind slabs to layers below in safe terrain - or simply navigate around steep wind loaded features on lower angle, planar terrain.

    (2/22/2022)

    Wind slab avalanche (likely human triggered) in West North. Southwest aspect @ 5200'.

    Photo: NWAC Public Obs

Avalanche Discussion

In addition to slab avalanches in wind loaded terrain, strong late winter sun combined with a few inches of new snow could create rollerballs, pinwheels, and even small loose wet avalanches. These are most likely to occur in steep, sun exposed terrain around or below cliffs or rocky, treed features. 

Observers in the Mountain Loop Monday found 2' of right-side-up new snow above a weak crust buried on February 19th. Thicker slabs were found in terrain loaded by west winds with the storm, but northeast winds have since eroded these down and redistributed snow to south and west aspects in West North and Stevens Pass. An annoying sun crust can be found on southerly aspects and older crusts are again at the surface in very wind exposed terrain. Detailed snowpit observations found 0.5mm facets between the February 19th crust and Valentine's Day crust just below, This weak layer produced sudden results with Compression Tests and propagation with Extended Column Tests. Deeper crust-facet layering from late January can still be found in shaded, alpine terrain. No new natural or human triggered avalanches associated with any of these crust-facet layers have been reported in the last week.

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