Bulletin d’avalanche

East Slopes North

Northwest Avalanche Center
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Danger d’avalanche

Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Expect a stormy day with strong winds and dangerous conditions to develop at mid and upper elevations. The new snow may bond poorly to weak surfaces that consist of faceted grains, surface hoar and slick crusts. Consider using lower angled slopes away from larger terrain features and in more sheltered terrain.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–2.5

    Westerly are picking up, and should peak on Sunday. As new snow falls, wind will quickly transport it into thicker and stiffer slabs on high, exposed slopes. The new snow has buried a layer of faceted grains, surface hoar and crusts. Its not just the new snow we're concerned about, its also the weaker structure below that which may become stressed. The crust from late January has become a problem in zones to the south, and north of the border, so it may just be a matter of time in this area.

    Because of the nature of these weak layers, avalanches may fracture widely across terrain features and could be triggered from adjacent and lower angled slopes. You can avoid the problem by seeking out sheltered terrain away from steeper slopes. Look for signs of instability like shooting cracks or whumphing collapses to clue you into danger. By the end of the day, the new snow may start to become reactive even in sheltered areas, so stay tuned into the changing conditions. 

    Example large natural slab avalanche from last year.

    Photo: Willie Webster

Avalanche Discussion

Expect a windy and stormy day on Sunday. Conditions should deteriorate as the front approaches in the afternoon, so keep your exits in mind. As new snow adds up during the day, instability should increase with it.

Over the past few days, observers have been finding weak surfaces. The wind may help knock down some surface hoar and break up some facets, but its unlikely to destroy all of it. 

On shady slopes, at mid and upper elevations, there is up to 1.5ft of recent snow over a stout crust from January 31st. Observers have found a thin layer of weak facets just above the 1/31 (elsewhere early February) crust. In the East Central zone, backcountry travelers have triggered a number of avalanches just above the crust, with the most recent being on the 22nd. With a stormy week ahead, we'll be watching the weak layer as a potential culprit for avalanches. Sunny slopes and lower elevations hold substantially less new snow over this crust and often don't harbor the associated facets. 

Snowpack information is limited outside of the Highway 20 corridor and Harts Pass. Let us know what you find if you get out into the backcountry!

Régions couvertes