Avalanche forecast

Stevens Pass

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Avoid steep slopes if you find more than 10" of newer snow because you could trigger wide or surprising storm slab avalanches on facets over a crust. Expect increasing danger, and dangerous conditions to develop as heavier snow moves in later in the day. Small loose wet avalanches may run with daytime warming at lower elevations.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–1.5

    As new snow adds up, look for shallow but reactive slabs on steep slopes. Expect dangerous conditions to develop as heavier snow moves in later in the day. Especially look for unstable snow on northwest to northeast aspects near and above treeline. This is where old snow is weakest; Where faceted grains rest above a crust from early March. The variable nature of faceted grains over a crust from early March could make for tricky conditions where some slopes avalanche but others don't. Look for shooting cracks and use small, steep test slopes to check and see how the new snow is bonding.

    Example shallow storm slab.

    Photo: Alpental Pro Patrol

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Wet new snow and warming temperatures may cause a round of small loose wet avalanches during the daytime. Look for wet sticky snow, rollerballs, and fresh fan-shaped avalanches to clue you into this avalanche problem. Use caution on steep slopes, and watch out for terrain of consequence once you find these signs. 

    Example human triggered rollerballs in shallow but wet sticky snow. Photo: Dallas Glass

Avalanche Discussion

Riding conditions may improve as new snow continues to cover old debris, but the warm nature of this storm may make for heavier or sticky snow, especially at lower elevations. With the new snow comes increasing avalanche danger. Incremental loading of weak, older snow may make for tricky and dangerous conditions on Monday. We've been tracking a layer of faceted grains just above a crust from early March, and every inch of new snow that accumulates adds to the slab over this structure, and it gets closure to failure. This is a good time step back, and plan tours that avoid lots of avalanche terrain. Check for soft, weak, sugary snow over a thicker crust. A stout crust formed during the last atmospheric river event on March 1st, and a few inches of snow accumulated over it. These grains became weak and faceted, and were buried on the 8th. On many shaded and upper elevations slopes, you can this find weak layer just above the early March crust. The weak structure may persist, and dangerous avalanche conditions may continue into the week or beyond.

Observers noted very small loose wet sluffs running fast on lower elevation slopes on Sunday. They also observed very shallow storm slabs that were triggered with daytime warming. In many areas, the shallowly buried and hidden, icy avalanche debris may still make for challenging travel. There was a widespread, natural avalanche cycle in most of the Cascades on February 28th, while the area received heavy snow, followed by heavy rain up to at least 6,500ft. The avalanche cycle in the Stevens Pass zone included multiple slides at size D2.5-3, and many smaller avalanches. Observers reported avalanches running on unusually low-angle terrain. Check out the avalanche database for details of some of these.

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