Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

You may still be able to trigger large avalanches on older layers of weak snow especially on northerly aspects at upper elevations. Before committing to steep terrain, use your probe or pole to feel for stiffer, wind-drifted slabs.  If you experience loud collapses in the snow, stick to lower-angle slopes. 

Avalanche problems

  • Persistent Slabs

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

    Avalanches involving persistent weak layers are difficult to predict and tend to stick around for a while. Even well after a storm, it may only take choosing the wrong piece of terrain to trigger an avalanche. With the uncertainty, take a step back and closely evaluate slopes that may harbor this weak snow.  Dig down and identify sugary, faceted layers or feathery surface hoar layers buried in the snowpack. You can also use snowpack tests to look for sudden or propagating results. Stay on lower-angle slopes if you experience whumping collapses or cracks shooting through the snow.

    The most likely location for triggering an avalanche is on higher elevation northerly slopes where the wind has drifted the snow into deeper, harder slabs. While not typically avalanche terrain, you could also trigger avalanches on steep slopes in the eastern foothills (see photo below). Be suspect of steep, open terrain below ridges, areas with stiff wind-drifted snow, steep rolls in the middle of slopes, and near rocks or cliffs. Some areas of older wind-drifted snow could now be covered up and be harder to visually identify by surface texture. Instead, use your probe or ski pole to identify areas where the snowpack is deeper than average or stiffer than the snow in sheltered areas.

    (12/10/2022)

    3ft deep persistent slab avalanche in a heavily wind loaded area at Mission Ridge

    Photo: Drew Carlton

Avalanche Discussion

On Thursday, Matt Primomo reported from Dirty Face Mountain and found surface hoar on shaded slopes and crusts on southeast through southwest aspects.

During the storm from 12/8-12/9, both natural avalanches ran on the mid-November facets at Mission Ridge and Crystal Mountain. These avalanches were both natural and triggered during control work and by skiers in backcountry terrain. We suspect that a couple of observed avalanches in the neighboring East North zone also involved older weak snow layers.

Many locations in the East Central zone have a weak snowpack structure with facets formed in mid-November buried near the ground. Most avalanches on these deeply buried facets are from northern aspects in wind-loaded terrain near and around Blewett Pass and Mission Ridge. Observations indicate that triggering persistent slab avalanches may be less likely in the Teanaway drainage and the Salmon La Sac areas. We still have some uncertainty about the snowpack. It's critical to make your own observations and be ready  to scale back your terrain choices if you see any red flag signs of instability or find weak snow layers buried beneath slabs of snow. 

The sun has been warming southern aspects, and now most sun-exposed terrain has a melt-freeze crust on the surface. I expect clouds to stick around most of the day especially as you move east of the Cascade crest. If you find yourself under blue skies, note that snow on steep, southern aspects may get heavy and wet. You could see roller balls or wet snow sliding off steep terrain near rocks or cliffs.

If you are out and about in the mountains, you can help us by submitting an observation. 

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