Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The slopes are primed for dangerous human triggered avalanches. These could be very large and break into old snow near the ground. Another big load overnight into Wednesday will only add to these dangerous conditions. Reports of very large avalanches and widespread collapsing in the Wenatchee Mountains should be enough to steer clear of slopes steeper than 30 degrees on Wednesday.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–3

    We know for sure that (at least) the Wenatchee Mountains are dangerous. Heavy slabs from solid dumps of snow the past few days are sitting over weak, sugary snow and crusts from December. Don't trust big, open slopes near and above treeline. Keep your distance from slopes 30 degrees and steeper, because this problem is unmanageable.  The most dangerous slopes will be steep, open starting zones, but unsuspecting slopes at mid elevations are candidates for these deep avalanches as well. Look out for obvious signs of instability like recent deep avalanches, whumphing collapses, or shooting cracks. The next couple of days will be a good time to be patient, and stay off of steep, open slopes as the storms continue to stress these deep weak layers. 

    Weak snow above a crust is a tricky and historically deadly weak layer east of the crest. This structure may be anywhere from 1.5ft to 4+ft below the surface, above roughly 5,000ft. In the Wenatchee Mountains, it appears most recent activity has probably been on the 12/21 crust (which is near the ground there). In the southern half of the zone, a few potential crust layers exist. In the northern half, weak snow above a crust from early December is more concerning, as the 12/21 crust did not form there.  

    (1/5/2021) This chunk of slope was observed to have failed on a crust from December 21st. It was triggered by a snowcat driving by at Mission Ridge.

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    You could trigger thick and cohesive windslabs in areas exposed to the wind. Look for shooting cracks and other signs of instability such as whumphing collapses or recent avalanches. If a steep open slope appears to have a firm or hollow sounding snow and is near or above treeline, avoid it, and steer clear of going underneath them. Cornices may easily break off and trigger avalanches on the slopes below as well. Recent windslabs have been very wide, and they will only be deeper and wider on Wednesday. There are a number of potential weak layers to be concerned about, so it will be best to stay off of, and out from underneath steep wind loaded slopes. 

    With all the deep new snow, loose dry avalanches may run easily outside of wind affected areas on Wednesday. Look for these fan-shaped slides that start from a point (also known as point releases). In steep terrain, these could entrain lots of snow, and create large avalanches. Roof avalanches may continue for towns like Leavenworth, where rain on snow is falling.

    (1/4/2021) Debris ran through the trees below Diamond Head from a large slide that likely occurred naturally on January 4th. This would be a bad place to go for a ride.

Avalanche Discussion

Following a set of solid storms for the eastern slopes, Wednesday will be the beginning of a break in the storm pattern. Make no mistake, we are still in the midst of this prolonged avalanche cycle. An observer noted a D3 avalanche off Tronsen Head on Tuesday. It carried a few large trees with its debris. On Monday, Mission Ridge and Leavenworth picked up 1.2" of Snow Water Equivalent, with 9" of dense snow at Mission Ridge and a natural avalanche cycle ensued. Many slides ran on the old/new interface, but some ran on older, weak layers. A large (D2.5) avalanche was observed on Sunday at 5,400ft in a sparsley treed burn zone near Lake Wenatchee. A D2.5 avalanche was observed from Big Slide Creek in Icicle Creek on Sunday as well. On Saturday, a 240ft wide avalanche was triggered by a skier from a distance at 4,700ft on a South aspect in the Salmon la Sac. Another 200ft wide avalanche was triggered by a snowmobile side-hilling on a SW aspect of Round Mountain that day. These were both about 1.5-2ft deep, and may have run on a recent suncrust. These avalanches may only be deeper and wider on Wednesday.

Many areas near the crest hold very deep snow from the past week. Be aware of tree wells, and tree bombs.

During the ongoing Covid-19 pandemic, continue to follow the latest guidance from local, state, and federal health officials. Avoid unnecessary risks that could impact first responders and stress medical resources. Wear a mask when appropriate, practice social distancing, and consider recreating closer to home.

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