Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
4 · High
Treeline
4 · High
Below
4 · High
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Highlights

7a UPDATE: AVALANCHE WARNING. Strong westerly winds with up to another 1-2 feet of snow will again form very dangerous avalanche conditions. Stick to lower elevation, wind-sheltered slopes. Avoid traveling under or on large slopes 35 degrees and steeper especially where the wind is depositing snow. Watch out for natural avalanches and the chance for unsurvivable very large avalanches.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2

    Expect natural avalanches on leeward slopes near and above treeline. Avoid wind-loaded, leeward slopes 35 degrees and steeper. Steer around thickly loaded, pillowed features and convex rollovers. Fresh wind slabs will grow bigger and become easy to trigger as the day goes on. You can expect the most dangerous conditions near and above treeline. Due to both fresh wind slabs and the potential for deep slab avalanches, you should avoid large avalanche paths, especially at mid and upper elevations. Below treeline, stick to wind-sheltered slopes and well-supported features. While you may not trigger avalanches as easily, they still may be likely on steep, open slopes. Even in sheltered terrain, watch for snow that slides easily on a recently buried crust on southerly slopes or on any convex, unsupported terrain feature.

    (11/22/2020) An example of cornices and wind loading from westerly winds on Rock Mountain. Photo: Josh Hirshberg

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–4

    The best way to stay safe is to avoid large avalanche paths and overhead start zones. Avoid traveling below large slopes 35 degrees and steeper. Slopes 5,000ft and higher and on sun-exposed aspects are of most concern. 

    With another rapid load of snow expected through Friday, it's too soon to take Deep Persistent Slab avalanches off our minds. On the 21st and 22nd, widespread natural avalanches ran big enough to destroy cars and houses. Some of these ran 2-3,000ft to the valley floor and involved a weak layer of facets and a crust that was buried in mid-January. While solar aspects appear to have been especially problematic, we know deep slabs have also run on shaded north and northwest aspects.

    (2/24/2021) A very deep crown (estimated at least 9 feet) on Tye Peak. This deep slab avalanche likely ran on February 22nd on facets above a crust buried on 1/24. SE, 5150ft. Photo: Josh Hirshberg

Avalanche Discussion

Expect the most dangerous conditions early in the day. The heaviest snow and strongest westerly winds will be Thursday night into Friday morning.  18" fell in 24 hours as of Friday AM, burying a sun crust on steeper, sunny slopes. weak snow may exist at the new/old interface on shaded slopes. Stevens Pass patrol reported windy conditions and triggering reactive slabs on leeward slopes.  From the 20-23rd, the Schmidt Haus weather station has registered about 6" of water equivalent. On the 22nd, rain fell on previously dry snow to about 4,800ft. The crust is now buried as deep as 3 feet. Numerous very large natural avalanches ran during that time:

Observers reported D3 sized natural avalanches on a ESE aspect at 5,200ft near Skyline Lake (in the Moonlight area). These were at least 7ft deep, knocked down trees, and may have run on the 22nd. A similar avalanche was reported on a SW aspect, near 5,100ft on Nason Ridge, just west of Rock Mtn. In the Scenic area, guides reported size D3 natural avalanches running on the mid-January weak layer 3-10ft deep on W-N aspects. Natural avalanches ran on SE and SW aspects of the Tunnel Creek area to D2.5. WSDOT triggered a very large size D3 in one of the Old Faithful paths on a SW aspect below treeline. Observers reported natural avalanches to size D3 on a SE aspect of Lichtenberg Mtn as well as a D4 sized avalanche on a SE aspect of Rock Mountain in Schilling's creek. This avalanche broke many mature trees and deposited debris 40 feet high near Highway 2.  On Sunday, observers reported a very large D3.5 natural avalanche in the historic Wellington slide path on a SE aspect of Windy Moutain. A very large avalanche (likely skier triggered) ran on the mid-January weak layer, 5 feet below the surface, on a S aspect at 5,000ft, below Skyline Lake.

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