Bulletin d’avalanche

East Slopes Central

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Points saillants

Very dangerous avalanche conditions are expected to develop with this storm. Avalanches may run naturally with the storm snow, and in some areas you could trigger an avalanche that becomes very large and runs on weak snow near the ground. Saturday will be a good day to stay off of and out from underneath steep slopes.

Problèmes avalancheux

  • Storm Slabs

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

    Expect a round of natural avalanches early in the morning on Saturday as heavy snow piles up quickly. Slabs could fail on lower density layers beneath, on recently buried layers of surface hoar, or even on old weak snow near the ground. Slides may be soft and small in nature, or they could be large and dangerous if they pull out old snow. Conditions may remain touchy during the day, and it will take time for the snowpack to adjust to this load. The underlying consequences of triggering even a small storm slab are that it could step down and slide on the ground. 

    Natural avalanches are expected, and human triggered slides will be easy to occur, so if you go out make sure you are confident in how to avoid avalanche terrain.

    (11/23/2022)

    A small storm slab on a boulder with a person for perspective.

    Photo: Matt Primomo

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–3

    The new snow will stress deeper weak layers near the ground. Slopes may be hanging in the balance, just waiting for a trigger to avalanche on Saturday. We know that some areas of weaker snow are in the eastern part of the zone from around Highway 97 and east to Mission Ridge. Steep, northerly aspects are especially vulnerable to avalanching because that's where this layer is weakest, and they may receive heavy wind loading. Saturday is not a great day to jump into any steep slope, especially at upper elevations where more snow may accumulate with wind drifting. Slides could be triggered from below or the edges of a slope in heavily loaded areas.

    (12/7/2022)

    A sled triggered avalanche on a road cut. On a larger feature, a bigger avalanche could have resulted. N at 6,200ft in Owl Creek.

    Photo: Matt Primomo

Avalanche Discussion

We're expecting a pretty significant upslope storm event for the East Central into Saturday. It's not quite mid-December and the snowpack is piling up even in the foothills. The cold weather has been a blessing and a curse. Great to have snow on the ground, but the cold temperatures have allowed weak snow near the ground to persist, and in very shallow areas it has grown weaker. On Thursday, 2-4" of new snow fell and covered up a range of older snow surfaces. This ranged from suncrust on steep southerly aspects, to stiff wind board or soft snow. Surface hoar was also fairly widespread and reported by numerous observers prior to Thursday, and now may be buried and preserved in a somewhat widespread fashion on open, wind-sheltered slopes.

Needless to say, Saturday will be a good one to steer clear of backcountry avalanche terrain and let the storm do it's thing. Sunday is also shaping up to be a dangerous day with the new snow load still stressing weak layers, but the call of fresh powder to contend with.

If you are out and about in the mountains, you can help us by submitting an observation. 

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