Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

There are tricky avalanche conditions in the East Central zone. You can trigger large avalanches on weak snow layers buried by the recent snow or older layers from Mid-November. Areas of particular concern are northern aspects in terrain with wind drifted snow near Mission Ridge, Blewett Pass, or the far eastern part of the zone. However, due to the spotty distribution of these weak layers, you should approach new terrain cautiously and use small, inconsequential test slopes to see how the snow reacts. If you see shooting cracks, feel the snowpack collapse, or the test slope produces a mini avalanche, you should stick to lower angle terrain. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2.5

    Many locations in the East Central zone have a weak snowpack structure, with the weekend's storm snow overlaying recently buried surface hoar and a deeper layer of weak, sugary facets from mid-November. Crusts overlaying these mid-November facets are beginning to break down, and recent observations indicate that this snowpack structure may be losing strength. Most evidence of avalanches on these deeply buried facets are from northern aspects in wind-loaded terrain near and around Blewett Pass and Mission Ridge. Add into the snowpack mix the recently buried surface hoar from 12/8, and we have a complicated snowpack throughout the East Central Zone. We have significant uncertainty about the distribution and reactivity of these weak layers. During the recent storm, avalanches ran on the mid-November facets at Mission Ridge, Crystal Mountain. We suspect that a couple of observed avalanches in the East North zone also involved older weak snow layers. These avalanches ran naturally, during control work, and by skiers in backcountry terrain. These weak snow layers take time to adjust to significant changes like the 12-24inches of snow that fell over the weekend. While the likelihood of triggering these large avalanches is decreasing, assessing the snowpack is essential before committing to steep slopes. 

    Steep, northerly aspects are the most suspect location for these deeply buried weak layers to exist. Be particularly 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 where you are more likely to trigger these avalanches.

    Dig down and identify sugary, faceted layers or feathery surface hoar layers buried in the snowpack. You can also use small test slopes to see if you can get a slab of snow to move. Stay on lower angle slopes if you find the overlaying snow slides easily on these layers, experience whumping collapses, or observe cracks shooting out from your equipment. 

    (12/10/2022)

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

    Photo: Drew Carlton

Avalanche Discussion

On Saturday, three large avalanches were reported from Mission Ridge, with ~3ft deep crowns. Most avalanches on this deeply buried weak layer have occurred near and around Mission Ridge and Blewett Pass. However, a similar snowpack structure exists in many places throughout the East Central Zone. While reports from the Teanaway and Salmon La Sac areas may indicate a decreased likelihood of triggering these avalanches, we are still gaining confidence in the spatial distribution of avalanches on this layer. Uncertainty and the spotty reports of these avalanches leads us to believe that there are other areas within East Central where these layers are more susceptible to producing avalanches. 

The sun has been warming southern aspects, and now most sun exposed terrain has a melt freeze crust on the surface. Another sunny day is in the forecast for Tuesday, and 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. Stay out from under cliffs or rock faces that begin to shed snow. 

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

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