Avalanche forecast

East Slopes South

Northwest Avalanche Center
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Avalanche danger

Fri
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

You may be able to easily trigger storm slabs during the earlier hours of the day - however as snow lines rise and precipitation changes to rain- the likelihood of you triggering a wet slab increases significantly.  A complicated weather forecast and overlapping avalanche problems should help keep your terrain selection simple.  Avoid all areas where avalanches can start, run, or stop. 

Avalanche problems

  • Storm Slabs

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

    Before the snow changes over to rain you may be able to trigger avalanches within the storm snow, especially at mid and upper elevations. As precipitation falls, temperatures will continue to rise, which will cause these storm slabs to be upside-down in nature and be quite sensitive to a human-trigger.  These may be widespread through the terrain, especially as snow lines rise slowly.  It won’t be hard to find hard-over-soft layering, cracking in the new snow, and test slopes failing easily.  Your best bet will be to avoid all slopes greater than 35 degrees on Thursday. 

    (12/20/2022)

    Storm slabs like this may be easily triggered on Thursday. 

    Photo: Public Observation

  • Wet Slabs

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

    Wet slabs are notoriously hard to forecast for and we have uncertainty with our weather forecast in-terms of when the snow will change over to rain and the amounts of precipitation we may recieve. What we do know is snow levels are on the rise - precipitation will change over to rain eventually- and we currently have a dry snowpack with weak layers present. Buried surface hoar and facets sitting on a crust could be possible interfaces that avalanches fail on.  As water percolates deep into our dry snowpack, triggering a large and destructive wet slab increases significantly 

    Any slopes steep enough to avalanche should be suspect.  Thursday will be a good day to dial it back and avoid traveling on and under slopes greater than 35 degrees. 

    (12/23/2022)

    Example: Natural wet slab avalanche below treeline at Mt Rainier. NW 3800ft early in this storm cycle. Similar slides could still occur in the East South.

    Photo: NPS Rainier Rangers

Avalanche Discussion

On Wednesday, Katie traveled into the Soup Creek area.  She traveled on multiple aspects and elevations around this zone and located buried surface hoar in specific areas on northerly aspects.  In places she did find it, it was 8-10 inches below the snow surface.  Check out her full observation here . 

Thursday will bring a very different story as a warm front associated with an atmospheric river lifts north.  This will bring rising freezing levels and precipitation in the form of snow changing over to rain. This complicated weather forecast comes with a bit of uncertainty regarding timing and precipitation amounts.  Whatever happens, will certainly test our snowpack. 

Going into this atmospheric river, the East-South had a complicated snowpack with buried weak layers in-form of buried surface hoar and facets sitting adjacent to a crust.  The neighboring east-central zone reported numerous human-triggered avalanches on these weak layers, especially surface hoar at mid elevations.  So as we head into this warming event, it will be critical to remember that wet avalanches could potentially run on these layers and be destructive.

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