Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

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

Expect dangerous conditions as snow continues to add up over a tricky snowpack. Many slopes may be approaching their tipping point, just waiting for a trigger. You could start large avalanches in upper elevation wind affected terrain, and could get surprised by steep open slopes in the forest. 

Avalanche problems

  • Wind Slabs

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

    Winds have been transporting snow at upper elevations into thicker slabs. Slabs may rest over weaker surfaces and could react in surprising ways. We don't have a great handle on upper elevations, but expect that large and wide avalanches could be triggered. One slope may avalanche, while another may not due to the variable nature of the old snow surface. NW-NE aspects are likely to hold weaker, faceted snow beneath wind slabs and are the most suspect. 

    Travel conservatively knowing that conditions may be dangerous. Give the new snow time to settle out before venturing into obvious large avalanche terrain features. Look and feel for wind stiffened snow as you gain elevation, and look for shooting cracks or whumphing collapses - these are signs of instability that should be heeded. 

    (1/31/2022)

    Large, remotely triggered wind slab avalanche on Shuksan Arm  in West North zone. NW aspect @ ~5400'. Rain-affected crust/old snow surface is visible as the bed surface.

    Photo: Liza Kimberly

  • Storm Slabs

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

    We've received over 18" of new snow, and it continues to trickle in. The storm snow is poorly bonded to underlying interfaces in some areas. Variable old snow surfaces are making for variable reactivity across different slopes. Some may be near their tipping point and only need a trigger, while others may not. Steep northwest through northeast aspects below around 4,700ft have held the weakest old snow surfaces, and may be the most suspect for initiating avalanches, but the jury is still out.

    This is a funky situation, because slopes may be more problematic at lower elevations than at mid elevations. Rethink your terrain selection below treeline, and travel as if you could trigger slides there. It would be wise to give it a few days before jumping into areas where avalanches are consequential. Monitor how the new snow is bonding to older layers, and look for whumphing collapses, and shooting cracks as you travel.

    (1/31/2022)

    Small fracture on a NW aspect at 4,000ft. This failed on very weak faceted grains within a crust/facet sandwich. Small whumphing was also observed on nearby slopes.

    Photo: Matt Primomo

Avalanche Discussion

Uncertainty continues around how well the new snow is bonding to older, weak snow surfaces. Around 18" of snow fell by Monday afternoon. Snowfall rates were fairly heavy Sunday night into Monday morning, and observers noted a few small natural avalanches even below treeline. Wind stripping and loading occurred throughout the daytime, and was intense at higher elevations. I noted small whumphing collapses and low propagating test scores in a very weak crust/facet sandwich at 4,000ft...very low in elevation. We don't have many new observations, so be sure to step off the skin track and make your own once in a while. Also keep an eye out for loose dry and loose wet avalanches, these could run in steep terrain on Tuesday if the sun comes out.

Prior to the storm, observers consistently found near-surface facets and surface hoar on a variety of shaded, northerly slopes below 4,700ft. Sunday's warm temperatures and mixed rain/snow may have melted these weak layers in some areas, but not all. Approach steep slopes with an assessment mindset and be ready to move to lower-angled terrain. Check out recent observations from the Upper Nason creek, Stevens Pass sidecountry, Jim Hill, and the Yodelin area. Let us know if you experience whumphing collapses or shooting cracks to better track these conditions.

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