Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 6 years ago.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

Highlights

With the first real lull in the weather in over a week on Thursday, you need to continue to stay patient and let the snowpack adjust to the large amount of water it just received. Make conservative terrain choices, staying on terrain less than 35 degrees and being aware of the effects wind or sunshine are having on the snow. Any triggered avalanche can grow large enough to bury or kill you.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    For over a week, Snoqualmie Pass has received storm after storm, resulting in 6-7 feet of new snow. With that volume of snow over a relatively short period of time, the snowpack will need time to adjust. There are multiple potential weak layers in the upper snowpack that could fail, requiring you to dial back your terrain choices and be cautious with your route-finding. Any triggered avalanche on Thursday could entrain enough snow to be large enough to injure, bury, or kill you. As one might guess, we do not have a lot of observations from upper elevations throughout this storm cycle, giving us a bit of uncertainty about conditions. What we do know is that there has been a natural avalanche cycle almost daily (or nightly) every day for the past week, with many paths running multiple times as they shed the most recent storm snow. The best indicator of avalanche potential is recent avalanches and we have had a lot of them the past week. So stick to lower angled terrain and give the snowpack a bit more time to heal. As winds increase later in the day, take note of wind-affected slopes where slabs could be thickened and possibly more reactive.

    (1/6/2021) These Storm Slabs failed overnight before being buried by continued snowfall. This has been the norm throughout the past week.

  • Loose Wet

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

    Speaking of uncertainty, there is a possibility for some sunshine on Thursday at Snoqualmie Pass. On Wednesday, some sun breaks had NWAC professionals noting snow shedding from rocks and trees, with fresh rollerballs. We’re not sure if there will be enough of a window of sunny weather to drive a Loose Wet avalanche problem, but it should be on your radar. If you find yourself in the sun and the snow surface is getting wet and sticky, you should head for shadier slopes. Loose Wet avalanches may be difficult to get moving, but once they do, they can entrain lots of snow and grow very large, even triggering slabs as they descend. At a minimum, you should be aware of other dangers caused by the sun on Thursday, such as tree bombs. There is a lot of snow currently sitting in the trees, and with warming conditions, these large masses could fall. Apart from the hazard of being hit by one directly, they could act as triggers when they hit the slopes, triggering slabs or loose avalanches.

    (1/6/2021) Crowns are visible from a natural cycle that occurred overnight, shedding the latest round of storm snow. On a return through the terrain in the afternoon, new rollerballs were observed from warming and light rain during the morning, crossing the previous skin track.

Avalanche Discussion

What a week it’s been at Snoqualmie Pass. For the past few days, it has generally been snowing 1-2 feet every 24 hours, triggering a natural avalanche cycle, then repeating. With so much active weather, it's no wonder we have some uncertainty around conditions. In some respects, it’s easy to manage. With that much snow over a relatively short period of time, just continue to give the snowpack time to adjust before stepping out into avalanche prone terrain. Pinpointing where and how avalanches may fail could be a bit harder. There are multiple potential weak layers in the 6-7 feet of new snow that could fail. Maybe the most sensitive ones have already failed during the continuous avalanche cycle the past few days. Maybe some are still waiting for you to come along and be the weight that pushes them over the edge. As we start to make our way into the mountains more and get some visibility around the zone, the signs of avalanches from the past week continue to present themselves to us. We have seen numerous small and large crowns around the zone and in some windows of good weather, have had visibility to upper elevations where potentially very large crowns were observed. These slides appear to have broken into deeper layers of the snowpack and highlight the potential for some isolated very large and destructive avalanches to occur, particularly above ~4500 feet where the snow becomes much drier. 

As you dig around to find out what’s happening in the snow for yourself, two layers serve as notable snowpack markers for you. On New Years Day, a crust was formed and buried at nearly all elevations. This may appear like an ice lens above 4000’ and may be about a meter below the snow surface. The prominent 12/21 crust still serves as a reference and may be found closer to 2 meters below the surface. 

In addition to dangerous avalanche conditions, non-avalanche hazards exist out there. Creeks are running high at lower elevations due to all the rain, large amounts of snow and branches are falling from trees, and the deep snow creates a hazard due to tree wells and deep snow immersion. Find out more information about deep snow safety HERE.

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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