Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 6 years ago.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

Highlights

Dangerous conditions continue as significant snowfall and wind have added a heavy load and stressed older layers of weak snow.  Stay far away from and well out from under wind-loaded, open terrain 35 degrees and steeper. Consider avoiding avalanche terrain at upper elevations where you can trigger very large and destructive avalanches that could break widely across slopes.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    3

    Persistent slab avalanches are difficult to manage and can catch even experienced travelers by surprise. The best way to stay safe is to avoid open slopes 35 degrees and steeper and put a large buffer of terrain between where you travel and all avalanche paths. Make sure to regroup and stop only in truly safe terrain, well away from and out from under steeper slopes. You may be able to trigger these avalanches from a long distance away.  Triggering avalanches is likely on recently wind loaded slopes, and they may be especially reactive on southerly slopes that are typically sun-exposed. While these avalanches may be less likely below treeline, you may still be able to trigger them in open terrain above 4,000ft. Signs of avalanche danger include cracks shooting through the snow, whumphing collapses, and recent avalanches. As the weak layer gets buried deeper, expect that you'll get fewer warning signs before an avalanche occurs. 

     About 3-4 feet below the surface, you can find a softer layer of snow above a crust that formed in mid-January. On Friday through Sunday, observers confirmed avalanches that broke widely and were remotely triggered on this layer. This snowpack structure can be found on most slopes, and there's uncertainty around how widespread these avalanches will be in the terrain. To be safe, approach any slope steeper than 35 degrees with extreme caution. When in doubt, avoid avalanche terrain.

    (2/6/2021) This slab was intentionally triggered by a small cornice drop on Saturday (2/6) in the Crystal backcountry. It propagated widely and is believed to have run on the Mid-January crust/facet combo. Similar avalanches have been reported from this zone. [E aspect, 6300'. Photo: Jeremy Allyn]

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    Watch for wind-stiffened snow, drifting, and actively blowing snow. Avoid leeward slopes where westerly wind has deposited thick slabs over the past 4 days. Avalanches will be bigger and easier to trigger above treeline. You may even be able to trigger wind slab avalanches in open terrain below treeline. Any slide could break into older weak layers of snow causing a very large and destructive persistent slab avalanche. Use caution near cornices and the edge of ridgelines. You may be able to trigger wind features and cornices very easily. 

    You may be able to trigger both loose dry and slab avalanches in storm snow on wind-sheltered slopes. Fluctuating temperatures over the past couple of days left soft light snow over a strong-over-weak storm layering in the upper snowpack. Whether you're in sheltered or wind-exposed terrain, you can use small, inconsequential slopes to check if the storm snow slides or cracks easily.

    Example storm slab on a small test slope.

Avalanche Discussion

The peak of avalanche activity likely occurred Saturday night. Observers got glimpses of slides on Sunday and submitted a flurry of avalanches observations. A very large natural D3 avalanche likely ran on the night of the 6th on a NW aspect of Jim Hill into the Lanham Creek drainage. We also have vague details of other avalanches in the nearby Henry Creek area on the 6-7th. After avalanche mitigation on Sunday, Stevens Pass Patrol reported triggering widespread and touchy loose dry and soft slab avalanches in the recent snow along with a few slopes still breaking 3-4 feet deep to the mid-January crust.

On Friday the 5th, I observed a very large and widely propagating persistent slab avalanche in Highlands Bowl (SE at 5,600ft) outside of the boundary of Stevens Pass resort. Professional guides reported huge collapses (whumphs) below Skyline Lake. Ski Patrol at the pass remotely triggered 2ft deep avalanches while skinning on a ridgeline. These were on northeast aspects at 5,800ft and ran on the mid-January crust facet layer. WSDOT triggered large avalanches in both new snow, and older snow early in the morning as well. One was a D3 avalanche (big enough to break trees) and ran on the same 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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