Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Tue
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Out of date — this forecast expired 4 years ago.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

Sustained westerly winds have formed stiff slabs in higher-elevation terrain. You could trigger small, recently formed slabs, or you could trigger a nasty 3ft deep hard slab avalanche. In areas with less than 3ft of snow and in the eastern Wenatchee Mountains, the potential remains to trigger large, surprising avalanches on weak snow near the ground.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    New snow has stacked up, and winds from the west quickly redistributed it near ridgetops. Westerly winds will continue to drift the very low-density new snow into thicker pockets near exposed features. Recently buried surfaces range from widespread surface hoar, facets and crust. The thing to emphasize here is that most surfaces were weak before this storm, and the new snow may not bond well.

    Look for signs of instability as you gain elevation, and check test slopes for cracking. Steer around steep slopes that appear freshly loaded, or if you find signs of instability. 

    (12/14/2022)

    Example photo showing blowing snow from alpine ridgelines.

    Photo: Willie Webster

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–2

    The last sign of instability involving this layer occurred on Thursday (that we know of) with whumphing reported east of Mission Ridge. Chances to trigger a deeper slab on old weak snow near the ground have gradually declined over the past few days, but with additional new snow and wind loading they will remain possible and are most likely in the eastern Wenatchee mountains where the snowpack is very shallow. It may only take choosing the wrong piece of terrain to trigger an avalanche. Check for weak snow near the ground, or a punchy feeling with stiff snow over weak snow to identify this concern. If you travel on steeper slopes on the north half of the compass, stick to well-supported features and know that you're taking some level of risk. 

    (12/10/2022)

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

    Photo: Drew Carlton

Avalanche Discussion

It will feel pretty arctic out there on Monday, so bring an extra layer or two and consider that a potentially stronger storm may arrive later in the evening. Visibility should improve on Monday, but the winds did some damage to exposed slopes.  You could expect to find anywhere from 6" of new snow near the crest to only an inch or two in the Wenatchees. You can still find many shallowly buried obstacles out there that could ruin your day. The snowpack is less supportable where it is shallow, and stronger where it is deeper than 3ft or so. The recent new snow has covered up a 'mixed bag' of surface conditions. Many surfaces were quite weak and faceted, so they may become another weak layer as the snow stacks up in the coming days.

On Saturday, Chelan County Mountain Rescue found a very shallow snowpack with a general lack of slab structure at lower elevations on the north side of Blewett Pass. On Thursday, an observer noted a collapse west of Mission Ridge, along with three slab avalanches, two of which were in unusual locations. Although isolated, it signals that we are not yet done with persistent weak layers buried near the ground. 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 basal facets were on 12/8 and 12/9, and observed from north and east aspects in wind-loaded terrain near Mission Ridge. One very wide avalanche was observed on the 14th in the East North zone near Twisp (see photo below). Further west, observations indicate that the snowpack is deeper and the weak layers are stronger in the Teanaway and the Salmon La Sac areas.

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