Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 4 years ago.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

Snowfall will slowly accumulate during the day, and winds will drift it into shallow slabs near ridgelines. Look for small, freshly forming slabs as you gain elevation. If you are traveling in an area with less than 3ft of snow on the ground, consider your terrain choice with lingering potential to trigger wide avalanches on layers of weak, faceted snow near the ground. 

Avalanche problems

  • Wind Slabs

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

    Westerly winds will drift the slowly accumulating new snow into soft and shallow slabs. Old snow surfaces are a mixed bag of crusts and facets, and it may not bond well. Look for signs of drifting as you gain elevation, and check test slopes for cracking. Steer around steep slopes that are freshly loading, or if you find signs of instability. Any heavily loading slopes could also begin to stress deeper weak layers, but we're not anticipating a large bump in deeper instability on Sunday.

    (12/14/2022)

    Example photo showing blowing snow from alpine ridgelines.

    Photo: Willie Webster

  • Persistent Slabs

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

    The last sign of instability involving this layer occurred on Thursday (that we know of) with isolated whumphing 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. It may only take choosing the wrong piece of terrain to trigger an avalanche. Stick to well-supported features on the northern half of the compass, or if you experience whumphing collapses.

    (12/10/2022)

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

    Photo: Drew Carlton

Avalanche Discussion

Light to moderate snowfall and moderate to stronger winds should continue through the day on Sunday. Visibility won't be all that great in many areas near the crest, so it may be harsh conditions in the alpine when combined with the cold temperatures and wind. The new snow will slowly improve riding conditions, but shallowly buried obstacles still exist. The snowpack is less supportable where it is shallow, and stronger where it is deeper than 3ft or so. This next round of snow will cover up a 'mixed bag' of surface conditions. Expect a few inches of new snow on fast, soft recycled powder with some surface hoar on shaded slopes, and various thicknesses of crusts on southeast through southwest aspects. These recently buried surfaces may become another weak layer as the active weather continues this week.

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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