Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Plan conservative routes as an approaching storm will increase avalanche danger with strong winds and new snow on Friday afternoon. You could trigger small wind slabs in actively drifting snow, and deadly persistent slabs in an older facet/crust layer. Listen for whumphing collapses as signs to stay off of steep slopes nearby.

Avalanche problems

  • Wind Slabs

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

    As a cold front approaches, winds should pick up to strong by the afternoon. Wind may drift the newly fallen snow into soft, reactive slabs as the day progresses. In general, the higher you go other more likely you may be to trigger small wind slabs. Look for direct signs of instability as you travel such as wind blown snow, shooting cracks. Thicker drifts and slabs are likely to be found on leeward slopes below ridgelines and exposed features in the alpine. Use extra caution anywhere you find wind-stiffened snow including on lower angle approaches because these slabs may be resting on weak, faceted grains and could break well above you.

    Unfortunately, we have more than just new snow avalanche problems. If you trigger an avalanche in the new snow, it could step down to a deeper weak layer and become a larger and surprising avalanche. You could also trigger persistent slab avalanches in wind drifted snow from the past week.

    Example intense wind blowing snow that could quickly create wind slabs.

    Photo: Shane Robinson

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2

    Whumphing collapses have been associated with a facet/crust combo from late January. You can find this crust/facet sandwich down 1-2ft and on most aspects above 5,300ft. We don't have observations of avalanches on these older snow layers yet, but it's likely just a matter of time with more snow/wind loading. Incremental loading events may begin to tip those scales on Friday, with increasing winds. As long as we are getting whumphing collapses, it's possible to trigger one of these avalanches.

    Persistent slab avalanches can break in surprising ways and be triggered on lower angle approaches. Plan conservative routes we collectively gain more information on the distribution and likelihood of this tricky avalanche problem. Choose slopes 30 degrees or less and put a large buffer between you and larger avalanche paths. Hold tight, it's not a great time to venture into complex avalanche terrain while this storm increases avalanche danger.

     

    (2/1/2022)

    A similar snowpack structure and avalanche concerns exists in the Stevens Pass zone: Very long shooting crack in a wind drifted slope on a north aspect at 4,000ft near Henry Creek. The slab failed in weak, faceted grains above a stout crust. The crack ran about 100ft long.

    Photo: Matt Primomo

Avalanche Discussion

Observers noted many whumphing collapses in Cutthroat, Wilow Creek, and West Fork of Cedar Creek on Thursday. Professionals found Sudden Collapse test results and propagating Extended Column Tests on a north aspect at 6,800ft. This was on the late January crust/facet sandwich, 20" below the snow surface.  Areas further east in the zone will have less recent snow sitting over the late January crust. Below treeline, specifically in the 5,300-5600' range in the Washington Pass area,  large surface hoar was widely observed and subsequently buried by 6-12" of recent snow.  Only small loose dry avalanches have been noted in very steep terrain so far this week.  

The cold front for Friday into early Saturday should change snow surfaces fairly drastically with new snow and very strong winds. Expect a bump to dangerous avalanche conditions later Friday afternoon and into Saturday because of it.

Regions covered