Avalanche forecast

Olympics

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Forecast updated 8:38 AM due to higher than expected snowfall amounts. Avalanche problem changed from wind slab to storm slab.

Dangerous avalanche conditions developed Thursday night at all elevations. You can easily trigger a storm slab 1 ft or deeper on slopes steeper than 35 degrees. Slabs avalanches will be largest and most consequential on the lee side of ridgelines, below sharp fresh additions to large cornices.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    Hurricane Ridge exceeded the snow forecast with 12" of snow forming a reactive slab overnight. Another 6" or more of snow should add to the storm slab throughout the day. Humans can easily trigger a 1-2 ft storm slab on any slope steeper than 35 degrees. These slabs will be largest and most reactive where moderate (15-25) southerly winds enhanced the snow accumulation. Use frequent small hand shears and test slopes to evaluate the storm slab. Avoid all open slopes steeper than 35 degrees until the new, unstable snow has time to settle.

    Example: Test slopes can give you a lot of good information about how new snow has set-up after or during a storm. This test slope shows that storm slabs are sensitive and propagating easily.

Avalanche Discussion

Recent mild weather created a strong crust on solar slopes and light faceted snow on shady slopes. Light precipitation during the day Thursday probably didn’t change conditions all that much. 

Conditions changed drastically Thursday night with 1 ft of reported snowfall at Hurricane Ridge along with strong southerly winds creating snowdrifts 8-9 ft deep in the parking lot. With continued high rates of snowfall into the day on Friday, anticipate mid-storm instabilities that you can trigger on all aspects.

New snow behaves differently when it falls on different surfaces. The old snow surface is quite variable -- firm crusts on the southerly slopes, light faceted powder on the northerly slopes, and breakable crust on the west and east slopes.  The take-home is that avalanche conditions may change significantly depending upon what aspect and elevation you are on. For example, we expect the new snow to be well bonded to the old snow surface at lower elevations and on non-wind loaded slopes, but the new/old snow interface may be more reactive where the snow falls on old crusts or surface facets. Take the time to assess the new snow stability when you change aspects and pay attention to cracking, collapsing, and rapid changes in snow density as you travel.

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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