Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Winds drifted the recent snow into stiff slabs where you could still trigger avalanches. Avoid steep slopes where drifted snow tends to collect, such as below corniced ridges, the base of cliffs, and alpine terrain features. Above treeline, avalanches could be very large and unsurvivable. Choose low-angle slopes in wind-affected terrain to reduce your exposure. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Another dose of snow and wind will keep the potential for triggering avalanches on lee aspects. While most of these wind slabs are likely to be small, some very large natural avalanches occurred over the last couple of days on steep north aspects in alpine terrain (observation). We have significant uncertainty surrounding the layers involved in these avalanches, but they likely ran on deeply buried crusts. The consequences of triggering one of these very large wind slabs are likely unsurvivable. There is even potential for these avalanches to run naturally if we see significant snow and winds on Sunday. Make conservative terrain choices to manage this uncertainty and avoid steep wind-loaded north-facing terrain above treeline. 

    At lower elevations, use visual clues such as textured surfaces, deep pillowlike drifts, or feel for stiff over soft snow layering to identify and steer around likely wind slab locations. 

    (3/11/2023)

    Crown of a very large avalanche in the Icicle Creek Drainage. We have a lot of uncertainty surrounding this avalanche problem. So it is important to make conservative choices in alpine terrain.

    Photo: Matt Primomo

Avalanche Discussion

Throughout the zone nearly 3ft of snow accumulated over the past couple of weeks, with much of that in the last 3 days. During these prolonged storm cycles we often have limited observations from higher elevations, but a brief break in the weather today showed signs of very large natural avalanches (D3) in alpine terrain. While, at lower elevations, it seems that the storm snow is relatively well bonded to old snow surfaces, the terrain above treeline is much more uncertain. Choosing conservative terrain in the alpine is the best way to manage this uncertainty.

The recent snow is piling up over a couple of intermittent sun crusts and a pair of rain crusts from Valentine's Day, which can be found 3-5ft deep. We suspect that the recent very large avalanches may have run on these crusts in the Icicle Drainage and Rock Mountain. We don't have much info yet on the extent of this problem, but as the stormy weather persists, so could the potential for these very large avalanches. The most suspect terrain is wind-loaded northern aspects above 6000ft. The Valentine's crust often presents as a crust/facet/crust sandwich, with weaker snow beneath the upper crust. Observations indicate wide variability in the structure and depth of this layer throughout the zone. Leading up to these avalanches, observers noted isolated signs of instabilities on this layer in the Icicle drainage and the eastern Highway 2 Corridor. 

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