Avalanche forecast

West Slopes Central

Northwest Avalanche Center
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Avalanche danger

Sun
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Winds will increase ahead of the coming storm, transport snow onto downwind slopes, and build small but unstable slabs. Use lower-angled terrain to steer around steep slopes where you identify recently wind-drifted snow.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    The trickle of snowfall in the last week actually put down a decent amount of light new snow. The snow depth over the early February crust ranges from 4” at the lowest elevations to 12-16” up high. With a westerly wind direction, different parts of the forecast zone could see big differences in wind speed and slab formation. Some areas could see sustained strong winds and intense wind transport, while others remain quite calm and have less avalanche danger.

    Blowing and drifting snow should show exactly which steep slopes are loading up. Track the snow depth over the stout crust to find thicker drifts. Pay attention to differences in snow stiffness as you gain elevation and change aspects to help pinpoint where fresh wind slabs are building. 

    Some portions of West Central saw up to 1’ of new snow overnight Thursday and - combined with strong winds - these areas could have locally higher avalanche danger. Take note of changing conditions and shift to simpler terrain if you find more signs of instability than expected.

    (1/4/2023)

    Snow drifting onto leeward slopes is the observation that should definitely make you say, "That is a place where there could be a fresh wind slab."

Avalanche Discussion

There is a low likelihood of seeing wet avalanche activity or similar signs of instability on Saturday. Clouds should thicken early in the day, temperatures won't get too warm, and light rain at lower elevations should hold off until the evening. That being said, if any or all of these weather inputs pan out differently than expected you could start to see rollerballs and small wet loose avalanches. 

The White Chuck Tripod recorded 7" of new snow on Friday morning and temperatures stayed at or below freezing at 5000'. Precipitation amounts varied across the zone with as little as 0.2" at some stations while the Alpine Meadows and Skookum snotels picked up about 1.0" of precipitation. This equates to over a foot of fresh snow at mid and upper elevations in some parts of West Central. Observers in neighboring zones reported no new avalanche activity other than small wet loose avalanches that initiated in steep rocky terrain facing the sun. Good snow conditions and minimal wind effects were found even at the highest elevations.

The west slopes and passes of the Cascades are likely quite homogenous when it comes to the current snowpack structure. Heavy rain two weeks ago wetted out the upper and middle snowpack well into upper-elevation terrain. Low elevations lost most or all of their snow. Now that the water has drained and the wet snow is hardening up, a stout crust buried in early February is kind of like a new baseline from which to measure snow depth.

Recent snowfall has generally come down with much less wind than usual.  Periods of clear sky and cool temperatures have enabled some faceting. In some places, faceted layers - and possibly some surface hoar - have in turn been capped by more snow. The current upper snowpack structure isn't alarming. But the path we took to get a foot of new snow was a bit different than usual. There are probably more, thinner layers than you are used to seeing in just a foot of snow.

If you make it out, please share what you found with an observation.

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