Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

Dangerous avalanche conditions will exist in the mountains due to an overnight atmospheric river. Depending on your location or elevation, these avalanches could be wet or dry. If you choose to enter the mountains, make plans that allow you to avoid traveling on or below slopes over 35 degrees.

On the volcanoes, you could find locally higher avalanche hazard due to significant snowfall at upper elevations.

Avalanche problems

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    We anticipate the majority of natural avalanche activity to occur in the overnight hours during the onset of rain on snow. However, wet avalanche problems have the ability to linger, so you may see some in the morning hours. Middle elevations should be the sweet spot for the most widespread avalanche activity. That’s where significant dry snow currently exists, and rain is sure to fall during this next event. Look for avalanches to fail within the snow sitting atop the 12/6 interface or even down at this crust in isolated locations. You should avoid any slope where an avalanche can start, run, or stop if you suspect rain is falling on dry snow, even if that’s far above you. 

    (12/6/2023)

    Example: A small wet slab that ran during last week's atmospheric river event in the East Central zone. 

    Photo: Katie Warren

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2

    Above the rain/snow line, we anticipate new snow to be heavy, creating an upside-down snowpack perfect for producing Storm Slab avalanches. This is especially true on the volcanoes, where high snowfall amounts are anticipated. You’ll need to dig down multiple feet to the 12/6 interface to look for heavy snow overlaying weaker snow, density changes, or snow failing in blocks during snowpack tests. Small test slopes or handpits may give you some indication of instabilities right near the surface, but won’t be enough to paint the full picture with snow this deep. If you see recent avalanches or determine that the snowpack is upside-down, avoid slopes over 35 degrees.

    (12/2/2023)

    A large natural avalanche that occurred at upper elevations during a period of high snowfall rates earlier this season. [SS-N-R3-D2-U]

    Photo: Crystal Mountain Pro Patrol

Avalanche Discussion

This atmospheric river is not expected to be as warm or as long as the one we experienced last weekend. We anticipate the majority of natural avalanche activity to be in the overnight hours as rain soaks our currently dry snowpack. The exception may be on the volcanoes, where you could find that higher snowfall totals manifest in more natural avalanche activity and very dangerous avalanche conditions at upper elevations. If traveling in these areas, be prepared to put dry snow avalanches in the forefront of your mind and consider avoiding all avalanche terrain.  

The depth of the 12/6 interface, which marks the end of our last atmospheric river event, varies across the zone. The snowpack is essentially the same throughout the West South, with wetted snow below the 12/6 and dry snow above. Multiple human-triggered and natural avalanches were reported in recent days in our zone as snow depth increased over the 12/6 and winds helped redistribute snow. We do not anticipate any avalanches to fail below the 12/6 during this next event.

More rain will not help our already bleak travel conditions Swollen creeks will intensify while holes, rocks, and other natural hazards will continue to be of concern.

Regions covered