Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Additional snow and wind Sunday will maintain dangerous avalanche conditions at all elevations. Avoid slopes greater than 35 degrees especially those with evidence of wind loading. Bring an extra cautious mindset as the potential for very large avalanches on deeply buried weak layers still lingers.

Avalanche problems

  • Storm Slabs

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

    The storm Friday/Saturday overproduced and the trend may continue Sunday. Expect to encounter 8-12in+ of recent snow atop variable old snow surfaces. Thicker and more reactive slabs exist in wind-loaded upper elevation terrain. With cold temperatures, additional snowfall will continue to accumulate at low elevations Sunday. The recent snow needs time to settle and stabilize. Fresh slabs will be reactive to human traffic in all elevation bands on slopes 35 degrees and steeper. In areas sheltered from the wind, loose dry sluffs may run far and fast in steep terrain and could even trigger slab avalanches as they run downslope. Carefully assess how new snow bonds to itself and old snow surfaces. Observers on Saturday reported touchy conditions with a poor bond at the February 11 interface. Watch for shooting cracks, collapses, and recent avalanches. Avoid large open slopes and convex rollovers and seek out lower angled and supported terrain.

    (2/13/2021) A small skier triggered storm slab (D1) on a north aspect at 5400ft in Lanham Creek that failed on weak snow at the February 11 interface.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Additional snow and wind continue to stress the snowpack, and the potential for very large deep persistent slabs remains possible. In areas above 4000ft, weak structure exists and doesn't give much confidence for the 4ft of snow resting above it. You probably won't get any warning signs such as shooting cracks or whumphs. If you do get a whumph on a steep slope, it could be your last. Wise backcountry travelers continue to stay well away from big, steep, and open slopes near and above treeline because of this. Put a large buffer of terrain between where you travel and large avalanche paths, especially wind loaded areas. Travel like the slopes could avalanche big, and make sure to stop and regroup only in truly safe areas.

    About 3-5 feet below the surface, you can find a layer of grainy, faceted snow above or around a crust that formed in mid-January. Sudden and propagating snowpack tests on this layer can indicate the potential for an avalanche. While these avalanches may be less likely below treeline, this weak structure can be found in open terrain above 4,000ft, so we can't rule it out.

    (2/7/2021) A two party involvement occurred on February 7th. Skiers triggered a very large (D3) avalanche which partially buried 2 people. The avalanche released on a NE aspect at 6,100ft on Jim Hill in the Stevens Pass zone.

Avalanche Discussion

Cold, low-density snowfall and steady winds will continue through the holiday weekend bringing dangerous avalanche conditions. Avalanches within new and wind drifted snow are likely on steep open slopes and could grow large. In some areas, the new snow may rest atop weak old snow surfaces with the potential for surprising and widely propagating avalanches. A lingering deep slab instability still weighs heavily on our minds and demands very cautious terrain and travel choices. In addition to a complex snowpack, very cold temperatures Sunday will increase the consequences of any incident, avalanche-related or otherwise. 

On Monday February, 8th, two motorized snow bike riders were caught and buried by a very large avalanche in the East Central Zone (See the short video in the media gallery below). Last weekend's storm added around 4ft of settled snow to the snowpack, and many very large and deep avalanches have been occurring. Reports of natural and human-triggered slides have continued to come in: Natural avalanches may have occurred on February 9th near Stevens Pass and Snoqualmie pass. These were on an East aspect at 5,800ft (Stevens) and a Northeast aspect at 5,000ft (Snoqualmie, see photo below). When very large natural avalanches occur days after the last snowfall, we should take a step back and rethink our confidence in any steep slope. A two party D3 avalanche partially buried two people on Jim Hill on Sunday. On Monday, Highlands Bowl ran (Southeast at 5,600ft). This slope was also the site of a widely propagating avalanche on Friday and skier triggered avalanches on January 27th.  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. Very large avalanches were observed on Upper Nason Ridge (photo below), Tunnel Creek (photo below), NE slopes 5,400ft above Lake Susan Jane, and NE slopes 5,400ft above Swimming Deer Lake.  

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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