Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
View on map

Avalanche danger

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Out of date — this forecast expired 6 years ago.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

Highlights

You may find changing conditions and hazards on Saturday depending on if you are traveling above or below the rain line. Be prepared for this variability by making constant observations and conservative decisions. If you see signs of unstable snow as you travel such as whumpfing collapses or shooting cracks, dial back your terrain choices.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Snoqualmie Pass has been dealing with Storm Slab problems for the past few days, and with another quick shot of moisture Friday night, that’s where we will keep our focus. Look for slabs to be deeper, drier, and more reactive as you ascend in elevation above the rain/snow line. This is also where the wind may be able to move any freshly fallen snow around to create deeper and stiffer slabs on leeward slopes, at the base of cliffs, or on the sides of gullies. These avalanches generally trigger more easily on slopes steeper than 35 degrees, convexities, and unsupported slopes. Luckily, there are plenty of inconsequential small terrain features which fit this description where you should test the bonding and sensitivity of any potential slab. If you find reactive pockets of snow or a poor bond, look to avoid similar terrain features.

    (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.

Avalanche Discussion

Following a storm earlier this week, there were multiple human triggered slab avalanches at Snoqualmie Pass. Most of these reported avalanches failed on a mid-storm layer about 2 inches above the 11/24 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. Additionally, Friday the solar input and rising freezing levels were enough to tip the scales and create some Wet Loose avalanches in the zone, with many of the main Granite Mountain paths running for all of I-90 to see. As we get a little more precipitation Friday night into Saturday, this past week is a good reminder that instability is often greatest during periods of rapid change. In the case of Saturday, you may step out of your car and find that it has rained and the avalanche danger is minimal. But as you ascend in elevation, or as conditions change throughout the day, the snowpack may change quickly and you should be prepared to adjust your mentality and travel plans. At lower elevations, there is still an early season snowpack, and with sun on Friday followed by rain Friday night, natural hazards such as rocks, logs, and open creeks may be more prevalent. 

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.

Regions covered