Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

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

The avalanche danger has eased, continue to practice safe travel protocols. You may trigger a small windslab near and above treeline where recent drifts rest over a crust. Large persistent slab avalanches are unlikely, though still worth consideration in shallow, rocky terrain and in the northern and western parts of the zone. Expect an increase in avalanche danger going into Wednesday with the arrival of a potent storm.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Scattered windslabs may rest over the most recent (12/21) crust at upper elevations. Slabs will be thickest in higher elevation, wind exposed terrain, and near ridgelines. Look at snow surface texture and feel for stiff snow over weaker snow to identify wind slabs. Use test slopes or snowpack tests to check how well these slabs are bonding. As always, avoid wind loaded slopes steeper than 35 degrees if you find signs of instability such as shooting cracks. You may be most likely to trigger one of these on very steep and unsupported slopes above treeline.

    (12/28/2020) Small ski triggered avalanche in the Crooked Couloir off Snoqualmie Mountain.

  • Persistent Slabs

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

    Persistent slab avalanches are still on our radar due to a weak layer of sugary snow that sits atop an icy crust from back in early December. This structure is one that is responsible for many avalanche accidents in this area, and continues to warrant respect, even though the chances of initiating a slide have decreased to unlikely. It is the consequences of triggering a slide that are paramount, because it could easily be large enough to bury or kill you. These dangerous and surprising avalanches can catch even the most experienced backcountry travelers. The best way to stay safe is to avoid the type of terrain where you are most likely to trigger one. Keep your distance from slopes 35 degrees and steeper that are open enough and tall enough to produce large avalanches. Watch for obvious signs of instability like recent avalanches, whumphing collapses, or cracks shooting through the snow.

    Look for weak snow just above a thick melt freeze crust roughly 1.5ft to 3ft below the surface, above 5,000ft. We suspect this is more problematic in the northern half of the zone, and closer to the crest where the dry snow exists above these weak layers. The most dangerous slopes will be at the higher elevations, in steep unsupported and rocky terrain. Recent southwest winds may created stiff slabs in some of this terrain. As recently as the 27th observers performed snowpack tests that indicated propagation is still possible with this layer of concern. I found it to 3ft below the surface on an east aspect at 6,600ft in the Near Treeline band near Chickamin Ridge in the Chiwawa Drainage. These layers are not a concern where you find a stout crust near the surface, such as areas further south and at lower elevations. 

    (12/23/2020) A crown of an avalanche that ran between Dec 19-20th on a NE aspect near 7,000ft in the Alpine Lakes Wilderness.

Avalanche Discussion

About 4" of snow has accumulated in the past few days in the eastern half of the zone, but the higher peaks near the crest have received closer to 8". Winds have shifted a few times and potentially created shallow slabs on all aspects in the alpine. Previous surfaces were a mix of slick melt freeze crust, near surface facets or surface hoar, and wind packed particles. As is typical for the eastern slopes, there is a lot of variability in snowpack depth. Just east of the crest you may find 6ft of snow at 6000ft, but at  that same elevation east of Highway 97 in the Wenatchee mountains you may only find a few feet of snow on the ground. 

A potent storm looks to arrive overnight Tuesday into Wednesday, increasing the avalanche danger significantly. 

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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