Avalanche forecast

West Slopes North

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Fresh slabs of wind drifted snow are the primary danger on exposed, mid and upper elevation slopes. Utilize a lower angled line to reduce the likelihood of triggering an avalanche in wind loaded terrain. Friday will be the last day of clear sky and warmer mountain temperatures - keep an eye on sun exposed terrain overhead.

Avalanche problems

  • Wind Slabs

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

    Gusty ridgeline winds redistributed dry, light snow onto south and west-facing slopes on Thursday. Though no avalanches were reported, wind plus snow available for transport are the main ingredients needed to build new wind slabs. They may bond poorly to smooth, firm crusts below. This could make them easier to trigger and run farther and faster than you expect. Observers reported windward slopes getting scoured down to and around old tracks while downwind slopes looked smooth and filled in. Cornices may be a poor indicator of where wind slabs lurk due to a less common (northerly) wind direction the past few days. You can use the same observations to identify and avoid steep, wind loaded slopes and terrain features on Friday. You can also stomp on inconsequential wind loaded features to gauge the reactivity of wind slabs in surrounding terrain.

Avalanche Discussion

Lighter wind, sun and higher freezing levels could produce rollerballs or other signs of instability related to loose wet avalanches Friday. Solar slopes have had a few days of previous sun exposure which helps limit loose wet activity. On the other hand, some south-facing start zones picked up fresh snow with recent wind loading. Dry, wind transported snow in sun exposed terrain will probably go through the warming cycle all over again.

Surface hoar and weak, faceted snow grains were found at the surface in shaded terrain over the last week. On the other hand, strong north winds likely damaged these fragile surface layers on the very aspects where they escaped the sun. Tomorrow is the last day of good visibility. If you are out in the mountains note where you see - and don’t see - undsitrubed weak snow hanging on at the surface. 

Buried surface hoar and deeper crust-facet layers still lurk in the middle and lower snowpack. No new avalanches related to either of these layers have been reported this week despite extensive backcountry traffic. Heavy loads like a smaller avalanche or landing (or not landing) a big drop might produce a large avalanche in any of these weaker layers that still exist in the snowpack. A big load of new snow or rain from a future storm might also wake up these layers and produce very large natural avalanches.

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