Bulletin d’avalanche

East Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Sat
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Recently formed wind slabs may be lurking under a few inches of light snow that fell at the tail end of the storm.  Use caution near steep open slopes below ridgelines where you might trigger a wind slab avalanche.  To the south of the zone (Mission Ridge, Icicle), surprising avalanches are possible where avalanches break on buried weak layers.  There's still a lot we don't know about the early season snowpack, so approach consequential terrain with open eyes and a cautious mindset. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Feel for wind-stiffened snow as you gain elevation and change aspects.  The firmer snow may be hiding under a few inches of fluff that fell at the end of Wednesday's storm, masking some visual clues. Following a significant winter storm with few direct observations, the bottom line is that you'll need to identify recent wind loading patterns when pushing into higher elevation and wind-affected terrain. 

    Wind slab avalanches triggered in the recent snow may be large enough to cause injury or worse.  Use caution when approaching the leeward sides of ridges where you encounter stiffer slabs, see recently built overhanging cornices or observe pillows of wind-drifted snow.  If you see signs of recent slab avalanches or shooting cracks, it's time to shift to lower angle slopes. 

    (11/27/2022)

    Cracking of wind-stiffened slabs near Stevens Pass Mountain Resort.

    Photo: Joe Dellaporta

  • Loose Dry

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–1.5

    There's a lot of fresh, soft snow out there to enjoy.  Before engaging with very steep wind-sheltered terrain, take stock of your surroundings.  Loose avalanches may be big enough to knock you off of your feet. These avalanches could push you into a dangerous area if you're not paying attention.  Even though the snowpack is building quickly, you could be injured by hitting shallowly buried logs or other obstacles. 

     

    (2/27/2022) A natural loose dry avalanche, size D1.5 that occured on February 27th, 2022. 6,500ft WSW, Cutthrout creek. Photo: Josh Hirshberg

Avalanche Discussion

Across the zone, an inch or more of water was recorded at area weather stations Tuesday through Wednesday night.  This likely translated into 12-18" of new snow with a growing snowpack at all elevations.  There was a slight warming trend towards the end of the heaviest precipitation Wednesday morning.  Snowdepths are healthy for early December, in the 3-5' range at mid-upper elevations and 1.5-2' even in the valleys and foothills. 

Prior to this storm, weak faceted snow was found above and below the late November crusts although no avalanche activity was noted on these layers.  We have less information about the distribution of weak snow near the ground throughout the zone. The most recent rain crust in the upper snowpack formed after rain fell up to about 7,600ft at Blue Lake Col on November 25th.  While observers have been out early season, we're receiving far less information than mid-winter as winter recreation and operations spin up.  However, we do have critical observations to the south from Thursday 12/1 where whumpfs and avalanches were reported in the Mission Ridge area, and observers noted collapses outside of Holden and up the Icicle.  Persistent slabs have been added to the East Central forecast.  If you're headed out to areas with shallower snowpacks and/or further east of the Cascade crest you may encounter a similar snowpack and the need to travel far more conservatively. 

Avoid an early season injury in areas with lower snow cover; be mindful of shallowly buried trees, rocks, and open creeks.  And brrrr...it doesn't look like it's warming up any time soon so make sure to bring extra layers and supplies to stay warm. 

If you're out, let us know what you see by submitting an observation.

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