Avalanche forecast

Snoqualmie Pass

Northwest Avalanche Center
View on map

Avalanche danger

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Out of date — this forecast expired 6 years ago.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

Highlights

Slopes are now primed for human-triggered avalanches at Snoqualmie Pass. Avoid slopes over 35 degrees or piles of wind-blown snow where triggering an avalanche is more likely. Deeper layers in the snowpack have been showing signs of life and should be taken seriously.  

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    Recent snow, rain, and wind that has dramatically changed the snowpack around Snoqualmie Pass should come to an end on Wednesday. These meteorological factors created plenty of potential failure points in the recent storm snow for avalanches. You will find that as you ascend in elevation, the snow becomes drier and slabs become larger, particularly in areas where the wind was able to deposit additional snow. Avalanches will be most likely on steep slopes over 35 degrees, convexities, near rocky features such as cliffs and gullies, or in wind-loaded terrain. Look for recent avalanches, shooting cracks, and failing blocks of snow in your pits and uptrack tests as signs of unstable snow. Choose terrain carefully to avoid those high likelihood areas on Wednesday.

    (2/22/2021) This very large avalanche (D3.5) started high on Denny Peak and ran full path (2500 vertical feet), under I-90, and then down into Franklin Falls where avalanche debris filled the pool. [Photo: John Stimberis/WSDOT Avalanche Crew]

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3

    We just had a lot of very large avalanches at Snoqualmie Pass and we haven’t even had the visibility to really look around yet. Due to the ferocity of the storm, we have not been able to investigate if any of these slides failed on the Mid-January crust or not. A very large avalanche crown on Red Mountain was photographed from the road and appears to be large enough and wide enough for us to suspect that it failed on the Mid-January crust. This persistent weak layer has begun to awaken all around the Cascades since Sunday with suspected slides now in the Stevens, East Central, and Snoqualmie zones. On Tuesday, pro patrollers at Crystal Mountain were able to confirm an avalanche on this layer in the neighboring West South zone which failed 5 feet deep and propagated over 100 feet wide. The depth of this layer in our zone is estimated to be 7-10 feet deep. Don’t tempt fate by entering large slide paths or big open slopes.

    (2/22/2021) This crown on Red Mountain was photographed from the road and is suspected to have failed on the Mid-January crust/facet combo on either Sunday night (2/21) or Monday morning (2/22). [S aspect ~5500'. Photo: Rachel Consolini]

Avalanche Discussion

Hazard is generally on a downtrend due to cooling temperatures and no new precipitation in the forecast for Wednesday. We do not expect a widespread natural avalanche cycle, but you will be able to trigger avalanches or may see some natural activity as the snowpack adjusts to the recent load. A lot of water was added to the snowpack in liquid form during this event, and it hasn’t all drained out yet. Keep surprising wet avalanches such as Glides on your mind as you travel, looking out for large glide cracks in the snow as indicators to stay far away. 

On Tuesday, continued snowfall containing a lot of graupel fell at the pass. If this weak snow gets buried by Wednesday morning, expect very reactive conditions. Additionally, a crust was formed below the rain/snow line from the atmospheric river event. This crust becomes less pronounced and more deeply buried as you ascend in elevation, and could make a nice bed surface for slides to run on. Snow on Tuesday was found to be not well bonded to this crust at lower elevations and human-triggered Dry Loose avalanches ran easily on steeper slopes. Alpental Pro Patrol reported storm and wind slabs running on this crust during control work. With sunshine in the forecast, the sun’s influence could help the snow “slab up” or shed from trees and rocks, triggering loose slides on steeper slopes. We haven’t made it up to ridgeline to take a look yet, but we have to believe that the cornices have really developed during this storm cycle as well. Give these monsters a large berth as they may be primed to act as large triggers on the slopes below, possibly capable of triggering those deep persistent layers. At this point, with so much recent snow and wind, multiple weak layers and failure points, and plenty of water in the snowpack, any triggered avalanche is capable of growing large and destructive.

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