Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
3 · Considerable
Treeline
3 · Considerable
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Out of date — this forecast expired 4 years ago.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

Expect dangerous avalanche conditions on Saturday. Avalanches may become easily triggered, and could fracture in surprising ways if they fail on buried surface hoar, facets, or crusts. With stormy and somewhat unusual conditions, Saturday will be a good day to make conservative terrain choices.

Avalanche problems

  • Storm Slabs

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

    Storm slabs may be easily triggered on Saturday, especially first thing in the morning. Look for signs of instability like cracking and recent avalanches. Slabs could fracture wider than anticipated if they fail on layers of buried surface hoar, facets, and/or a thin crust from earlier in the week. Avalanches could become 1.5ft deep, especially in areas of wind loading like near ridgelines. You can use test slopes to check and see how upper layers are reacting, but it's not the day to trust many steep slopes. Buried surface hoar is 'spatially variable' in that you may not find it 7 times out of 10, but those 3 times, well... 

    We also have some uncertainty with deeper layers of the snowpack above 6,000ft, and on the eastern edge of the zone. Here, more snow may accumulate, further stressing these layers.

    Example photo of a small storm slab.

Avalanche Discussion

This is a somewhat unusual storm, in that the passes should receive less snow and water than areas further east. It's also a somewhat unusual snowpack set up, where a layer of buried surface hoar sits underneath a very thin zipper like 'drizzle crust' from earlier in the week. I found a few areas where previous wind drifting had overlaid slabs on this layer on Friday. For the most part, the snowpack was soft and not very wind affected. However, in those areas with some wind stiffening, I was able to get fast and clean fracturing. The failure layer often involved buried surface hoar, just underneath the thin crust and was down about 8" then. You can look for surface hoar under the surface on wind-sheltered slopes. Shovel tilt tests work well to discover it, as it is often hard to find with a small amount of very soft new snow on top. This layer could be well over 1.5ft deep on Saturday, especially in areas of heavier wind loading. There's an old saying 'unusual situation's can cause unusual avalanches'. This is a good thing to remember on Saturday.

Layers of weak snow and crusts were buried by a series of storms in mid to late November. This layer is now near the ground, and has been observed to be gaining strength and rounding. These older layers generally haven't been a problem for avalanches in this zone as much as in the East Central zone, though future storms could be enough to activate deeper layers. It's still early season and the snowpack may be hiding shallowly buried hazards of rocks and stumps, especially at lower elevations. Let us know what you see by submitting an observation!

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