Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Moderate to strong winds formed stiff slabs of drifted snow on many aspects where you could trigger an avalanche. These slabs may be easier to trigger where they rest over softer, weaker snow layers. Choose lower-angle terrain where you find stiff snow drifts below ridgelines, the base of cliffs, and steep rollovers. 

Avalanche problems

  • Wind Slabs

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

    Windy conditions will persist overnight on Friday before tapering off on Sunday. Identify and steer around steep terrain with stiff, textured drifts. Cracks shooting through the snow is a sure sign that these wind slabs are unstable. A few inches of new snow may hide some textured surfaces, so you can also use your hand, probe, or pole to feel to hard over soft layering in the snow. 

    Some wind slabs may be stubborn to trigger, but where they formed over weaker snow surfaces, they could be quite reactive. While larger avalanches on older weak layers remain unlikely, they may not be impossible. There are still weak layers capable of producing surprisingly large avalanches. 

    (3/18/2022)

    An example of a crack shooting through the snow on a steep wind-drifted slope. 

    Photo: Josh Hirshberg

Avalanche Discussion

We're on the cusp of a relatively stormy weekend, and precipitation will slowly increase throughout the day on Saturday. Temperatures are on a warming trend, but easterly pass-level winds should help keep things cool. 

On Friday, NWAC forecasters near Lichtenberg found widespread, variable wind-affected surfaces. This wind effect was significant even in typically wind-sheltered terrain. In the area they traveled, these wind slabs were stubborn. However, in a snow profile, the wind-stiffened snow rested over faceted snow and surface hoar and slid easily in shovel tilt tests. They found the January Drought Layer (JDL) buried approximately 2 feet deep. While the JDL was notably weaker than the overlaying snow, stability tests were unremarkable. They also noted natural, small, dry loose sluffs in steep terrain. On Thursday, observers in the Lanham Creek area reported widespread blowing snow and sensitive, shallow wind slabs near the ridgeline. 

We are uncertain to what extent the upcoming storms might affect these more deeply buried weak layers, but persistent slab avalanche conditions could become active. Stick to an "assessment mindset," step into new terrain slowly, and assess the snowpack for strong over weak layering before committing to steep terrain. Choose lower-angle slopes if you find a stiffer slab over weak, surgery snow or experience collapsing/cracking. 

The cold, mostly dry conditions in mid-February formed a potential new weak snow at the current snow surface. In some areas, stiff wind-slabs formed over this layer, while in others the weak surfaces are still on the surface.  With Sunday's storm, this new interface could prove to be sensitive, and avalanches could be easy to trigger.

The Stevens Pass Zone picked up 2-3ft in the first week of February, burying the JDL. Following the initial storm, there were numerous reports of whumpfing collapses and some shooting cracks, but no reports of associated avalanches in this zone. In zones to the south and west, there were numerous reported persistent slab avalanches on the layer. Sunny days produced small wet and dry loose avalanches and formed a melt-freeze crust on southerly slopes. We're monitoring the JDL, as it's still weak and close enough to the surface to be a problematic weak layer with big enough future storms. 

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