Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

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

New wind slabs will form on atypical aspects and cross-load some slopes as East winds re-distribute recent dry snow.  Avoid steep open slopes below ridgelines where you see obvious signs of wind-loading.  Wind slabs can grow larger and more dangerous in areas that have received more recent snow like White Pass, St Helens, and the Paradise area.  Bundle up - very cold temperatures and wind chills are forecast for all areas. 

Avalanche problems

  • Wind Slabs

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

    Winds have done a 180 from our storm cycle earlier this week.  East winds can surprise backcountry travelers used to certain slopes or aspects that are more commonly wind-loaded during a typical storm pattern.  Pay attention to which way the wind is blowing, literally, and avoid large open slopes below ridgelines where you see active wind-loading occurring.  Navigating safely above treeline will be difficult as some slopes become cross-loaded and fresh wind slabs develop.  

    At lower and mid-elevations, you're likely to encounter blowing and freshly drifted snow as well.  Ease into the terrain by using smaller and less consequential slopes to see how the snow reacts. If you find cracks or feel firm hollow snow underneath you, step back and stay off of these suspected wind-loaded areas.

    In areas that haven't received quite as much recent snowfall over this storm cycle,  like the Crystal Mt area, you can still encounter fresh wind slabs ridgelines but there just isn't as much snow to move around.  In these areas, the avalanche hazard will likely be a notch lower than the rest of the zone. 

    While the wind will be the primary concern on Thursday,  in wind-sheltered areas it's still possible that you could trigger a storm slab avalanche on steep unsupported rollovers or more likely, a small but fast-running dry loose avalanche in very steep terrain.  Don't let a smaller avalanche knock you over and take you for a ride above a terrain trap.

    Example from last season of East Winds transporting snow onto the opposite side of the ridgeline (and opposite recent cornice growth) from where we typically see Wind Slabs forming

    Photo: Andy Harrington

Avalanche Discussion

Avalanche Fatality: Colchuck Pk, East Central Zone: Read the preliminary report here.

There's been a wide range of storm totals in the West South Zone over the last few days with several inches of water translating into 1 or more feet of snow for areas like White Pass, St Helens and the Paradise area.  Areas that were shadowed from the higher precipitation totals, like the Crystal Mt and Chinook Pass areas, saw substantially less snow (and rain) over this period.  The strong to extreme westerly winds that were recorded Monday night with snow showers had pivoted to easterly winds on Wednesday as temperatures dropped into the teens and even single digits.  Several inches of low density snow fell on Wednesday, further improving conditions.  White Pass pro patrol reported that east winds had begun to pick up and the new low density snow was moving onto west aspects Wed afternoon.  In those areas with more recent storm snow, natural dry loose or sluff avalanches were reported in steep terrain.

We expect most avalanche activity to remain in the new snow above the recent rain crust/refreezing wet snow. However, we can’t rule out an isolated avalanche breaking into deeper layers like the 2/17 or 2/13 interfaces. This would most likely occur in isolated areas with a larger trigger like a cornice or a smaller avalanche that steps down deeper in the snowpack.

However you recreate on Thursday, throw on some extra layers, and whatever else you need to stay comfortable and warm in case of an unplanned emergency.  It won't feel like March is around the corner over the next few days.

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