Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

An impactful warm storm will bring rain, snow, wind, and dangerous avalanche conditions. You could easily trigger avalanches in the new snow, particularly where the wind deposits snow into deep drifts. Very large avalanches on deeper layers are possible in isolated areas in high alpine terrain. Make conservative travel plans and stick to low-angle slopes while the storm runs its course.

Avalanche problems

  • Storm Slabs

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

    A warming storm will deposit heavier snow over the recent light dry powder we enjoyed recently, and storm slab avalanches will likely become easy to trigger on slopes above 35°. Avoid common trigger spots such as steeper, unsupported convexities even in lower angle slopes. It will be a great day to stick to low-angle terrain and look for signs of instability, such as recent avalanches or shooting cracks. Using simple hand pits and test slopes, you can quickly assess how the new snow is reacting. If the new snow slides easily, you could trigger an avalanche on a steep slope. 

    While most avalanches will likely involve just the new snow, 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 layer involved in these avalanches. We cannot yet say if these are isolated or just the start of the types of avalanches we could begin to see. Regardless, the consequences of triggering one of these very large wind slabs are likely unsurvivable. The only way to manage this uncertainty is to avoid steep wind-loaded north-facing terrain above treeline. 

    As you would expect, moderate winds will accompany the storm. Wind slabs will form overnight and continue to build during the day on Monday. Look for actively blowing snow and drifts behind rocks and trees to identify the wind direction and avoid steep wind-loaded slopes.

    (1/8/2023)

    Example of a small storm slab in terrain below treeline.

    Photo:

  • Loose Wet

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

    It's been a while since our last Cascade rain event, and while this storm isn't exceptionally warm, we will likely see rain below 3500ft. Previous sun and warm temperatures may have formed crusts that will hold off wet avalanches initially. Still, you can expect wet loose avalanches as the rain saturates the snow at lower elevations. With recently buried crusts on some aspects, you could also see isolated wet slab avalanches. These avalanches may start naturally with trees or cliffs shedding snow onto steep slopes, but you can also trigger these avalanches while skiing. Pay attention to overhead hazards and avoid getting caught in your sluff in steep consequential terrain. 

Avalanche Discussion

Observers over the weekend reported a generally good bond with old snow surfaces, wet snow at lower elevations, soft dry snow on northern aspects, and a sun crust on solar aspects. The incoming storm will bury these variable surfaces, and adjacent slopes may have different avalanche potential. Therefore, evaluate terrain carefully as you travel and be prepared for a wide range of snow conditions. With this storm, there will be a west to east precipitation gradient, so anticipate more snow and greater danger closer to the Cascade Crest. As snow and winds pick up, be leery of overhead cornices that have grown large during the recent windy weather. They could fail and trigger avalanches on the slopes below. 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 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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