Avalanche forecast

Olympics

Northwest Avalanche Center
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Avalanche danger

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

Widespread weak snow sitting on a crust will make it easy for you to trigger dangerous and surprising avalanches on Sunday. Slabs will be the largest in the most heavily wind-drifted snow and can be triggered from ridgelines or lower angle slopes below. Avoid open terrain on or connected to slopes 35 degrees or steeper.

Avalanche problems

  • Persistent Slabs

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

    A large and widely propagating slab triggered on or stepping down to persistent grains on Saturday has us quite concerned about weak snow grains overlying the 1/13 crust going into Sunday. The weak snow isn't going away and with 6-10" of snow on the way we're more than doubling the snowpack above the 1/13 crust. Winds should continue loading the same W-N-E slopes they have been for the past several days.  Expect large persistent-style wind slabs near and above treeline that you can easily trigger. Well below ridgelines, you can still trigger shallower persistent slabs in less wind-affected areas that propagate widely and entrain all the snow above the crust. Persistent slabs can be triggered from the slopes below or from ridgelines. They release suddenly and are difficult to escape. Reactivity will be widespread. Whumphs, shooting cracks, and sudden settlements all confirm the problem. Give a wide birth to all open slopes steeper than 35 degrees on Sunday.

    (1/30/2021) Large human-triggered persistent/wind slab. 10" crown.

Avalanche Discussion

Human-triggered avalanches have been easy to trigger the last few days and they were growing larger by Saturday. On Saturday, riders remotely triggered a D1.5 (small-large) avalanche from the slope below. The avalanche had a 10" crown and propagated widely on a N-facing bowl near Victoria Overlook. The slide appeared to step down from a warming crust within weak snow to the stout 1/13 crust below.

On  Thursday and Friday, Professionals easily triggered 4-6" wind slabs in specific terrain features and shallow loose dry avalanches running on at stout crust. They found recent low-density snow averaging 2-4". Light to moderate sustained SSW ridgetop winds Tuesday through Wednesday morning transported the snow into 6-8" wind drifts. These drifts initiated from a density change within the wind slabs.   The new snow and drifts lie over weak snow (facets) just above the stout 1/13 rain crust. On a NE aspect, observers found a thin temperature crust within the weak snow.  See an excellent observations here for more information.

Another public observation from Friday found whumphs and hollow-sounding wind slabs as they headed to higher elevations, reminding us that these wind slabs are resting on weak snow.

We are awaiting more information regarding the potential burial of a second persistent layer: large-grained surface hoar stuck around on W-N-E aspects below ridgelines on Friday.

Despite the recent snow, wind transport of snow from southerly to northerly aspects has exposed icy slopes, and patches of bare ground. Make sure you can safely arrest a fall before crossing icy slopes.  

2020-21 Forecast Schedule: Avalanche danger ratings will be issued for the Olympics every Friday through Sunday and during mid-week holidays. During the week when the Hurricane Ridge road is closed, forecast information will be updated daily to include expected conditions and relevant travel advice under the No Rating label.

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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