Avalanche forecast

East Slopes North

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Natural avalanches with both wet and dry snow are expected Saturday night into early Sunday morning. Strong winds may cause continued loading of upper elevation slopes during the day. The hefty storm load will create dangerous conditions for all elevations on Sunday, as many slopes may only need a trigger to release. You may trigger avalanches from a distance or from below on connected slopes. 

Avalanche problems

  • Persistent Slabs

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

    Continued reports of loud whumphing on a variety of elevations tell us that weak snow above and below a crust buried in early December is continuing to be stressed. This layer may be 20"-36" down from the surface. There may be a layer of buried surface hoar a few inches above this crust as well. Persistent slabs dominate the way we travel, and plan to travel in the backcountry because all slopes steeper than 30 degrees are suspect. A 36" deep, and potentially very wide avalanche could be unsurvivable. 

    The heavy storm load Saturday night may tip the balance and cause natural avalanches on these layers. Below treeline rain on dry snow may cause wet slab avalanches to run. At upper elevations, strong wind through the day may continue to stress these layers. Listen closely for whumphing, and look for fracturing of large sections of snow while traveling. These are direct signs that the snowpack is unstable. In this case stay well away from any steep open slope, but I wouldn't wait until you get a whumph because it could turn into an avalanche in the wrong location. With lots of wind drifting expected to occur, any shallow wind slab that you initiate near the surface could step down to the crust, and become a large and destructive avalanche. 

    (12/18/2020) Example of a widely propagating persistent slab that surprised experienced backcountry travelers in the Stevens Pass zone. The slide was triggered from below.

  • Loose Wet

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

    Loose wet avalanches could be triggered or run spontaneously during the day. These could be large, and may gouge down to the early December crust. You will probably see evidence of recent activity if you look around at steep hillsides, as many naturals may run overnight Saturday into Sunday morning. Signs of loose wet instability are rollerballs, and wet sticky snow that entrains as it moves downhill. If you sink in deeper than your knee into wet snow, there is danger of deep loose wet avalanches on steep slopes.

    The best way to manage large loose wet avalanches is to avoid going on, or underneath very steep slopes, even in forested terrain if the trees are spaced out. 

    Example large loose wet avalanches

Avalanche Discussion

This storm will surely be a whopping load, with heavy snow, strong wind, and, rain up to 4,000ft or higher. Previously the storms have been incrementally loading a weak snowpack structure surrounding a crust from December 9th. Slides have been triggered from a distance, and run on this crust near Washingotn Pass on the 18th. They've also been reported from surrounding zones such as near Mt Baker and east of Stevens Pass. Below about 5,000ft and east of Washington Pass, this crust presents as a translucent freezing rain crust. Above and west of there, the 12/9 presents as more of a thicker and rough melt freeze crust. 

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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