Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 2 years ago.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

Highlights

You could still easily trigger a large avalanche in wind-drifted snow on steep slopes below ridgelines or in sheltered areas on weak layers below the recent snow. While the likelihood of avalanches decreased slightly, the travel advice has not. With these tricky, lingering problems, settle into enjoying travel on low-angle slopes in simple terrain. 

Avalanche problems

  • Wind Slabs

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

    Recent strong winds, low-density cold snow, and slick or weak surfaces are a setup that makes wind slabs stay reactive for longer than usual. Wind slabs that feel very stiff and supportable could break above you or broader than expected. Avoid steep slopes below ridgelines, the base of cliffs, and cross-loaded terrain features. Textured surfaces and visible blowing snow are great visual clues to identify wind-affected terrain. Cracks shooting out from your equipment are another key sign that these wind slabs are unstable. 

    We have a lot of uncertainty, particularly at the upper elevations, about the distribution and reactivity of this problem. The very weak snowpack structure has largely kept us and other observers out of upper elevation and wind-drifted slopes, limiting our direct observations of wind slabs. Simply avoiding steep wind-drifted slopes is the best management practice for our current snowpack setup. 

    (2/16/2022)

    Small wind drifts would crack and release easily off ridgetops on Wednesday. Shortly below the ridge we didn't find any wind affected snow.

    Photo: Nate Hough-Snee

  • Persistent Slabs

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

    The current snowpack is tricky, variable, and dangerous. Honestly, we can't tell you where you might get surprised by triggering a large avalanche on persistent weak layers. The variable old snow surfaces make the distribution of this problem hard to isolate, but we expect it to be most likely in sheltered, shaded, northerly terrain. Consider avoiding steep terrain on the north side of the compass, especially in sheltered areas like open, gladed slopes. Whumping collapses are a bullseye sign of unstable snow, and you should stick to low-angle terrain.

    Many areas don't have much of a cohesive slab over these persistent weak layers, and the layer isn't consistent throughout the terrain. Two adjacent slopes might have very different stability. This makes it a tricky problem to pin down and also one that won't be quick to go away. It might even get worse as the storm snow settles and gains cohesion. The safest terrain management option for this problem is avoiding it altogether by staying on low-angle terrain or moving to southern aspects. 

    Smaller storm slabs and fast-moving, dry-loose avalanches still exist throughout the terrain. These problems are more straightforward but add to the complexity of our current snowpack. 

    (1/19/2023)

    An example of a persistent slab in gladed terrain, like you might be able to trigger.

    Photo: Ryan Minton

Avalanche Discussion

The main takeaway from the current snowpack is that it is very weak, and it's nearly impossible to determine where you might run afoul of a persistent slab avalanche. I haven't seen this much variability throughout the terrain often. So, while it might seem like there isn't much going on, it's really just because folks are heeding advice and not venturing into steep or complex terrain. As we get further from the storm, these problems can lure us into a false sense of security, especially if the snowpack stops sending us loud collapses as warning signs. Avoid a "stepping out" midset, while we get a better understanding of this complex snowpack. 1-2ft of recent snow fell on widely varying surfaces. Stevens Pass Ski Patrol and WSDOT avalanche forecasters reported mostly small storm slab avalanches, with a few larger wind slabs, releasing on the old surface or within the new storm snow. The new snow fell at very cold temperatures and lacked cohesion, so backcountry users reported more dry loose avalanches than slabs. Another observer reported a propagating extended column test on a layer of faceted snow, and observers throughout the zone reported widespread collapsing. Overall, the results are mixed, but we're concerned with lingering instabilities on the January Drought Layer (JDL) on these northerly aspects. 

I was out in the Henry Creek Area on Sunday to check on the state of our weak snowpack. Traveling through the low-angle clearcuts, we experienced numerous localized collapses. I found two layers of concern in snow profiles. The deepest layer is buried 20-23in down and consists of 1-2mm faceted grains over the 1/10 crust. Above that, buried 15-20in, is the surface of the January Drought Layer, which is 1cm buried surface hoar over another layer of 1-2mm faceted grains. I also observed a deep crown on a steep southern aspect at 5700ft, likely a wind slab that occured during strong winds on Saturday. 

You can help us build that data set by submitting an observation HERE or via the Avy App. 

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