Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 6 years ago.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

Highlights

Be prepared to make your own observations Friday to determine how the snow may be changing along with the weather, then adjust your mindset and travel plans accordingly. If you experience clues of unstable snow such as shooting cracks or whumpfing collapses as you travel, dial back your terrain choices. If the snow surface begins to get moist, head for shaded slopes, staying aware of the terrain above you at all times.

Avalanche problems

  • Storm Slabs

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

    Reactive Storm Slabs formed this week may still be lingering in the Snoqualmie Pass zone on Friday. Look for slabs to be deeper and more reactive as you ascend in elevation or where the wind was able to thicken potential slabs on leeward slopes, at the base of cliffs, or on the sides of gullies. Hand-pits and test slopes can help determine the bond and sensitivity of any potential slab. If you find reactive pockets of snow or a poor bond, avoid slopes steeper than 35 degrees, convexities, and unsupported slopes where you could trigger avalanches more easily.

    (11/25/2020) Test slopes can give you a lot of good information about how new snow has set-up after or during a storm. This test slope shows that storm slabs were sensitive and propagating easily in the Alpental Valley on Wednesday.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    With the freezing level set to rise and the sun primed to make an appearance for some of the day tomorrow, keep the possibility of Wet Loose avalanches in the back of your brain. It’s not often an avalanche problem we think about this time of year, but with these rising temperatures, it may not take much solar input to help destabilize this week's snow and create some avalanches. Friday should become increasingly cloudy, so the possible window for these avalanches could be short, but if you feel the snow surface heating up, you need to be aware of your exposure to avalanche terrain. If you notice rollerballs, snow shedding from the trees or rocks, or see fan-shaped avalanche debris, seek out shaded terrain away from sun-exposed slopes above you.

    (2/23/2020) Rollerballs like these are a great indication that the snow surface is becoming wet and unstable. They can be the precursor to loose wet avalanches.

Avalanche Discussion

We are another day removed from the storm that dropped well over a foot of snow on the mountains of Snoqualmie Pass, resulting in an avalanche cycle. Observations were limited on Thursday about how the storm snow was settling out, but we do know that there were multiple human triggered avalanches on Wednesday. Most of these reported avalanches failed on a mid-storm layer about 2 inches above the old snow interface with some slides propagating widely and wrapping around terrain features. Slides were as deep as 16 inches in areas where the wind was able to drift the snow into deeper piles. Looking for freshly built cornices, textured snow surfaces, or pillow-like piles of snow as you travel can help to identify these potentially deeper areas to avoid. And with the sun coming out tomorrow, there is the potential to destabilize the snow on steeper slopes. Don’t get caught in a difficult spot if the sun starts to warm the snow surface. Remember that it’s still early season and there are many natural hazards on or just below the snow surface. Taking a ride due to even a small avalanche could be consequential.

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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