Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

If you stumble into a combination of thicker, wind drifted snow over crusts and facets you could trigger a large and surprising avalanche on nearby steep slopes. Be wary of any slope facing the north half of the compass, and check for weak, sugary facets beneath the storm snow. Whumphing collapses and long shooting cracks are signs of instability you might find, and should be heeded.

Avalanche problems

  • Wind Slabs

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

    Winds have been drifting snow at all elevations into thicker slabs. Though they are still fairly soft in most areas, they could be larger and more dense in alpine terrain. Slabs may rest over weaker surfaces and could react in surprising ways. NW-NE aspects are likely to hold weaker, faceted snow and are the most suspect. These aspects have consistently produced collapsing and shooting cracks in the low 4,000ft range (quite low in elevation). There is uncertainty with higher elevation, alpine terrain but expect that large and wide avalanches could be triggered. One slope may avalanche, while another may not due to the variable nature of old snow surfaces. 

    Travel conservatively knowing that you could trigger a surprising avalanche in some areas. Monitor how the new snow is bonding to older layers, and check for weak faceted grains over a stout crust beneath the storm snow. 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

Avalanche Discussion

Over the past two days, observers have reported shooting cracks or whumphing collapses on northerly aspects in the low 4,000ft elevation band (Stevens Pass proper, Yodelin, and Henry Creek clearcuts). The storm snow appears fairly well bonded to underlying moist snow surfaces at mid elevations. Uncertainty continues around how well the new snow is bonding to older, weak snow surfaces at higher elevations. In many cases even though you could find over 2ft of new snow, there just isn't a cohesive slab...yet. Storm totals since the 30th are around 20". Winds have been consistently from the west, and stripping and loading has been noted in many areas. Be sure to step off the beaten track and make your own observations once in a while. Also keep an eye out for loose dry and avalanches, these could run in steep terrain on Wednesday. With another storm coming in for Wednesday night into Thursday, danger is expected to increase.

Prior to recent snowfall, near-surface facets and surface hoar were found to have survived 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 at mid-elevations, but perhaps 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. Check out the new snow climatology which came out on Tuesday.

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