Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

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

The new snow needs more time to stabilize, especially above treeline where wind transported snow created deeper slabs.  Gather information as you gain elevation and don't rush into bigger terrain just because it's been 24 hours since the end of heavy snowfall. The possibility of triggering a very large, deep avalanche warrants caution above treeline.

Avalanche problems

  • Storm Slabs

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

    On Saturday a rapid accumulation of new snow triggered a round of natural avalanches at all elevations in West North. Less avalanche activity was reported from Stevens Pass and Snoqualmie Pass as those zones picked up much less snow. Though storm slabs often gain strength and quickly become unreactive, human triggered avalanches still occurred through the afternoon. There is up to 2’ of new snow out there and it wants more time to stabilize. You will find deeper slabs of new snow in wind loaded terrain. Start your day with low angle slopes and take time to assess layer bonding and observe avalanche activity from the storm. Definitely steer around steeper, unsupported slopes where you are more likely to trigger one of these avalanches. Consider avoiding all slopes greater than 35 degrees to mitigate uncertainty about triggering an avalanche.

    If the sun makes it out in the morning look for signs of instability like rollerballs and small loose snow avalanches that might change your plan for the day.

    (3/19/2022)

    Widely propagating, naturally triggered storm slab avalanche low in Swift Creek. This many other avalanches in the new snow occurred during heavy snowfall at the start of the day on Saturday. D1.5 - south aspect @ 4300'.

     

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3

    Three very large (D3) avalanches were reported on Wednesday from the Baker area - two natural and one from avalanche control work. They likely released on a layer of weak facets buried on March 8th. They remain a concern not only in alpine terrain where they initiated but also at lower elevations where they deposited large debris piles. As the layer in question gets buried deeper, triggering one of these avalanches is more difficult. With the end of heavy snowfall it's also less likely one will release naturally - but it could still happen. If you are caught in one it will be big and generally unsurvivable. A large load like a cornice fall, smaller avalanche initiating in higher terrain, or a group of people on a slope could trigger one where a single person might not. This isn’t really a “manageable” avalanche problem that can be figured out and mitigated with snowpits and other assessment tools. You are either in the terrain where it could happen or you are not. If you chose to travel these areas you are simply accepting a slightly higher risk of triggering a very large avalanche. 

    (3/16/2022)

    Deep slab avalanche triggered on the Shuksan Arm with control work.

    Photo: Adam Ü

Avalanche Discussion

This latest storm delivered more snow than expected in a very short period of time. Avalanche danger exceeded the forecast across West North - especially in the period from sunrise to about noon. Weather stations in West Central received 1.25" of precipitation with a bit more on the way with the convergence zone. Heather Meadows in West North picked up about 1.5” of precipitation in 12 hours with other areas like Schriebers seeing similar accumulations (and avalanche activity). Snow doesn’t like rapid change - if it gets too warm or too much load too quickly it acts out. Despite limited visibility through the morning, many of the observed avalanches were impressive. They were not necessarily deep (most were 30cm or less, slightly deeper in wind loaded terrain) and the ones that could be seen were D2 in size or less. On the other hand, some propagated very wide with crowns wrapping around terrain features in ways not normally seen. Slopes that did not avalanche naturally were easy to trigger with a few kicks from lower angle terrain above. 

 

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