Bollettino valanghe

West Slopes North

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Look for an increase in wind speeds as a storm approaches this weekend. Stronger winds will 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

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    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. 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. 

Blue skies and powder snow prevailed over much of the forecast zone today after last night's snowfall. Heather Meadows - with 0.2" of precipitation and 4" of new snow - was actually on the low end. Other snotels saw 0.3-0.4" of precipitation adding up to 6-8" of new snow over what we got earlier in the week.  Observers reported minimal wind effect at upper elevations and very good riding conditions. Avalanche activity was limited to small wet loose avalanches on south-facing slopes, many of which initiated in steep, rocky terrain. Expect crust on south aspects on Saturday.

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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