Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The danger is a tricky Moderate and its not time to tee off yet. Near and above treeline is where you'll find the largest and most overlapping avalanche problems; Beware of persistent slabs, wind slabs, and loose slides. Remember, you can always default to lower angled slopes away from large, steep or wind loaded features for some great powder conditions. 

Avalanche problems

  • Loose Wet

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

    Loose snow slides could take many forms, from dry to moist to wet.  Wet loose slides could pack the most punch, and we expect these to be easy to trigger after a few hours of direct sunshine. Dry loose have been running fast and far on steep slopes as well. Monitor snow surfaces as the daytime warms up and on slopes receiving sun. Wet gloppy snow and rollerballs are also good clues to wet loose slides. Check to see how the snow is reacting before jumping into features that could sweep you down and give special consideration to terrain traps. Move well away from potential runout zones of your partners.  

    (1/19/2023)

    A Wet Loose avalanche from a tree bomb at Snoqualmie Pass [S 5200'].

    Photo: Zack Novak

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–2.5

    On Thursday, the third skier on a slope triggered a large and surprising slab 1-2ft deep on a NE aspect at 6,200ft. It ran on large surface hoar on firm bed surface, triggered from the shallower area. So, contrary to popular belief, we still have a persistent slab problem. The slide even broke through the MLK crust which was about 5mm thick in this location. 

    Friday looks to be a really nice day, but it's time to rethink how you travel with these dangerous avalanches in mind. You might be most likely to trigger one on N-E aspects above 6,000ft, on the east side of the pass. Treat steep slopes that fits this description with a large amount of skepticism, identify and avoid them.  You could dig down and look for feathery surface hoar about 2ft down. Unfortunatley, distribution is variable throughout like aspects and elevations, so even if you don't find it in one place, that doesn't mean its not hiding out in another. 

    (1/19/2023)

    Large avalanche on a layer of buried surface hoar. NE at 6,200ft on Jim Hill. The crown was 1-2ft deep.

    Photo: Ryan Minton

  • Wind Slabs

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

    Recently formed wind slabs may remain easily triggered in certain areas. The distribution of slabs may be patchy, but they could be quite reactive. Check to see how the snow reacts on small test slopes. Look for punchier deeper drifts, cornices, and textured snow surfaces to identify likely slabs.  Steer around steeper slopes if you find shooting cracks, or thick slabs in large terrain features where getting caught in a slide could be less than ideal. 

    Consider the persistent slab problem described above, and the chances for slabs to step down and become much larger and destructive.

    (1/19/2023)

    Wind drifting at ridgeline above White Pine Cirque

    Photo: Josh Hirshberg

Avalanche Discussion

The recent front brought up to 10" of new snow to the pass, and a bit less further east. The ski triggered slab described above should serve as a focal point to folks planning their day in the mountains. It was a surprise to the experienced folks who triggered it, and it was a surprise to this forecaster. Its a testament to how tricky our snowpack has become in the Cascades at the moment. Don't let yourself get surprised out there, we now have this bullseye information regarding a persistent weak layer.

About 6" of new snow was reported from higher elevations by the afternoon on Wednesday. Observers reported being able to trigger small loose slides that ran fast and far on steep open slopes. Wind had been drifting snow near ridgetops and creating thicker slabs. General travel conditions have markedly improved with very good powder being reported. With another handful of inches of snow and cooling temperatures overnight, this trend shoul continue. Thursday should bring some sun, so keep that in mind and expect to see it's influence on snow surfaces on southerly aspects. 

On Monday, Brooke Maushund and I went to the Lake Valhalla area. We found a slick and slippery crust beneath about 4" of new snow. We were able to trigger small loose avalanches, both wet and dry on steep test slopes. The last cycle of wet avalanches occurred between the 13th and 16th while it rained to at least 6,000ft in the zone. You could still stumble into large, chunky debris.

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