Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Very dangerous avalanche conditions are developing - this is not your average PNW snowpack setup and instability may last longer than usual. Storm slabs could be easily triggered at all elevations and even in the trees. Stay off of and out from underneath steep slopes as large avalanches could be triggered from a distance or from below. 

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1.5–2.5

    As the next storm comes in, so do the reports of easily triggered avalanches, shooting cracks, and widespread weak snow surfaces. This is not your average PNW snowpack setup, and we expect that the storm snow will be easily triggered during the daytime on Monday. Slabs may react in surprising ways, and could be initiated from a distance, from the sides of steeper slopes, or beneath them. Open pockets in the trees could produce unsuspecting avalanches. Slides could be larger and deeper at higher elevations, where wind has created thicker slabs over the past few days. 

    Watch your slope angles, stay off slopes steeper than 30 degrees and well away from large, steep features. Look for signs of instability such as recent slab avalanches,  shooting cracks, and whumphing colllapses. Very large avalanches have been occurring in the West North zone on a deeply buried layer of surface hoar. A very large avalanche was observed off Mt Mastiff from around the 26th in this zone. While these very large avalanches may be unlikely, this storm could begin to tip the scales. 

     

    Example storm slab from earlier in the season. 

    Photo: Josh Hirshberg

Avalanche Discussion

Observers late in the afternoon on Sunday found easily triggered, shallow storm slabs associated with the weak snow surfaces at the new snow/old snow interface. Widespread very weak snow surfaces have been documented in many places throughout the Stevens Pass zone. The new snow is covering up very large surface hoar, sharp faceted surfaces and very low density stellars in most places and elevations. On southerly aspects, there are a couple of thin suncrusts with faceted grains between. Check out this ob from Lichtenberg on Friday which documents that layer well. At higher elevations, there are thicker wind slabs resting on faceted grains underneath the newer snow. 2.5ft down there are weak surfaces associated with the Solstice crust. 

As we head into this next storm cycle, we could begin seeing avalanche activity in unusual places. Slabs will begin failing at the new/old interface, but could begin stepping down to deeper layers. A very wide, very large avalanche ran off the E Face of Mt Mastiff around the 26th, and we could begin to see more avalanches like that. Unfortunately, the powder party with relatively good stability is over for now, and we need to adjust our mindset accordingly. 

Regions covered