Avalanche forecast

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Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Fresh wind slabs may be reactive on upper elevation, exposed slopes where and winds have drifted snow across them. Look for signs of instability like cracking or recent shallow slab avalanches as you gain elevation. Some observations report an icy crust that formed on the front end of the storm, so be advised you could hit a slippery crust beneath the new snow on some steep slopes.

Avalanche problems

  • Wind Slabs

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

    Look for signs of drifted, textured and rippled surfaces as you gain elevation. The more exposed a slope is, the more likely you could find wind drifted snow. Check for signs of instability like shooting cracks. Cornices are also a clue that past winds have blown, and you could find fresh slabs beneath them. 

    Steer around large, steep slopes, especially if you find signs of instability. Use well supported terrain and make careful evaluations before entering steeper slopes. In some areas, the crust that formed on the front end of the storm could prove slippery and make for a good bedsurface for fresh slabs.

     

    (1/5/2023)

    Example human triggered wind slab from about a month ago.

Avalanche Discussion

Observer Brooke Maushund toured at Washington Pass on Monday, and reported 6-7" of new snow during the day with a sharp gradient in snowfall amounts further east. No new snow had fallen at the end of rd Highway 20. A breakable rain crust was found at lower elevations, and became thinner higher up. The crust tapered away between 6,300ft and 7,000ft near Washington Pass. New snow was well bonded to older surfaces, but some isolated areas of wind affected snow were producing some cracking. Other observers noted an icey crust beneath the new snow, and intentionally steered around convex and freshly drifted features. With strong sun, loose slides should also be on your mind throughout the day on Tuesday. Pay attention to how the snow reacts during the day.

The very warm temperatures produced a round of small loose wet slides on Sunday, some coming to the edge of the closed Highway 20. Surface hoar was widespread on Saturday, but likely melted down in most places on Sunday. On Friday, observers near Harts Pass reported a recent cornice fall that triggered an 18" deep, and wide avalanche on an east facing slope (see photo below). This slide ran on a thin crust, and stepped down another few inches to faceted grains. The rest of the snowpack was facets to the ground. This is an unusual snowpack structure for the zone, but it's worth keeping on your mind if you plan to venture to this area, or perhaps the far eastern edge of the zone as well. There are a few layers that we've been tracking in the upper snowpack. Aside from the February 3rd interface, the Jan 5th surface hoar (about 2-3ft below the surface) had previously been widespread and problematic in snowpack tests. With time and rounding of the grains, these layers have strength. However, these weak layers are more likely to be problematic during or shortly after any loading event, and to the far north or far east in the range. 

Between February 3 and 8th, almost 2 feet of snow accumulated near Washington Pass. Observers reported a number of large (up to size D3) avalanches in the zone during this time. Crowns were mostly in north to east facing terrain, below cliff bands or in other wind-loaded terrain. One human triggered slide near the Lyall Glacier stepped down to a recent interface and broke into a large avalanche on an east aspect at 6,400ft. 

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