Avalanche forecast

East Slopes Central

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

An avalanche cycle is expected to continue into the morning hours with a saturated snowpack, and strong winds drifting snow near ridgetop. You could trigger very large and destructive avalanches at upper elevations, and above 5,000ft in the Wenatchee Mountains where weak, old snow may fracture near the ground. Wednesday is a good day to avoid avalanche terrain altogether, and let this meaty storm run its course. 

Avalanche problems

  • Wind Slabs

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

    Very strong winds will create intense snow transport at upper elevations and exposed locations on Wednesday. Wind slabs may release naturally into the morning hours and could be very large. Signs of wind slab instabilities are shooting cracks, whumphing collapses, and recent slab avalanches from leeward and crossloaded slopes. In addition to wind slabs, you may continue to find storm slab instability with heavy, dense snow over dry snow. These could happen on any slope steeper than 35 degrees, and outside of wind affected terrain. At higher elevations, wind and storm slabs could be up to 3ft deep.

    Wednesday is a good day to avoid avalanche terrain altogether,  and let the rest of this meaty storm run its course. To stay safe you'd want to stay well away from any steep slope. In addition to slabs on the surface, deeper weak layers exist above 5,000ft in areas with a shallow snowpack, such as the Wenatchee Mountains. Any avalanche could step down to these old weak snow layers and create unmanageable and destructive avalanches.

    (1/5/2021) Example hard slab that ran on a persistent weak layer in the Wenatchee Mountains.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    Heavy rain over a previously dry snowpack will continue a wet loose avalanche cycle that started on Tuesday. Even if natural activity begins to subside, a person will be able to easily trigger them on steep slopes. Wet slides could easily be large enough to bury and kill a person. Signs of wet loose instability include rollerballs, wet sticky snow over dry snow, and recent fan shaped avalanches. If you punch into wet snow past your boot top, that is also a good indicator that these could occur. Avoid going underneath steep slopes, even if it's on a trail through the trees as wet loose slides could run through open forested terrain. 

    All bets are off for the Wenatchee Mountains where weak snowpack structure, combined with heavy rain could also create wet slab avalanches. Best to give avalanche terrain a wide berth on Wednesday in areas with a previously shallow snowpack such as the Wenatchees. Wet slabs are difficult to predict and can be unmanageable.

Avalanche Discussion

What a storm (and likely avalanche cycle)! Round 2 of 3 of the Atmospheric River Train came in with a punch on Monday night into Tuesday. Many locations in the zone picked up 2" of snow water equivalent. Sasse Ridge Snotel took the cake with 20" of snow and 3" of SWE. Temperatures climbed steadily during the day, and a natural avalanche cycle was reported in Tumwater Canyon. Neighboring Stevens Pass had a very widespread cycle with some wide avalanches. Mission Ridge Ski Patrol reported very touchy conditions with long shooting cracks, remote and sympathetic triggers, and avalanches to D2+ in size. Most avalanches were very wide and 10-15" deep, with some likely deeper. They also reported a few very large whumphs. Last weekend, there was a Special Avalanche Advisory in place for the Wenatchee Mountains near and east of Highway 97 due to persistent slab avalanche problems, and the potential for avalanches to break near the ground. The recent very large whumphs experienced at Mission are a sign that deeper persistent layers are awake once again. 

The forecast comes with uncertainty about how the snowpack will hold up but punchy, wet snow conditions are a good bet. In any case, conditions will be dangerous to very dangerous, and travel in avalanche terrain is not advised on Wednesday. 

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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