Bulletin d’avalanche

West Slopes South

Northwest Avalanche Center
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Danger d’avalanche

Tue
Alpin
4 · Fort
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

A second, more significant atmospheric river is aimed directly at the West South. Rain-on-snow events are reliable avalanche producers and will drive the hazard up throughout the day. Your best bet is to stay out of avalanche terrain until these storms wrap up.

Problèmes avalancheux

  • Wet Slabs

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

    Expect natural avalanches to occur on slopes over 35 degrees as rain continues to soak the snowpack. Areas and elevations that did not see significant rain on Sunday will be primed for more widespread avalanche activity on Monday. You may initially notice loose avalanches, but eventually, more dangerous slab avalanches will fail due to a weak snowpack structure. These slides could travel long distances on open slopes and entrain much of this season’s snowpack. On smooth rock ledges or grassy slopes, the entire snowpack could fail. Traveling in avalanche terrain is not recommended. 

    (12/2/2023)

    Large natural avalanches occurred on the Throne at Crystal Mountain—the larger of which connected terrain features and spanned far distances.   [SS-N-R3-D2-U]

    Photo: Crystal Mountain Pro Patrol

Avalanche Discussion

This next atmospheric river should be more potent and warmer than the one we’re wrapping up on Sunday evening. Due to the nasty weather, we didn’t receive much information about how conditions played out on Sunday. Much of the travel advice and messaging will drift over to Monday (and then Tuesday) as we continue to soak our early-season snowpack. 

That said, Monday will be a little different than Sunday. 

  1. Many areas of the zone have already seen the initial onset of precipitation on dry snow. Meaning the initial shock to the snowpack has already happened. That could make these areas better suited to accept more rain and, hence, less avalanche activity—especially at lower elevations.
  2. Cool temperatures and a break in the rain on Sunday evening will allow a surface crust to form on slopes that got damp on Sunday. This could delay avalanche activity for a brief period during Monday's initial onset of rain. But it should eventually break down.
  3. Freezing levels are skyrocketing during the day to 8000’. This means that upper elevations will be seeing rain for the first time. These areas will be prone to more widespread avalanche activity.
  4. There will be a transition area from wet to dry snow as you ascend in elevation. Expect to find plenty of avalanches in these areas. This elevation will vary across the zone.

Of course, there are exceptions to all of these points. We are dealing with plenty of uncertainty around snowpack and weather conditions during this early-season period. On Saturday, natural avalanches, whumpfing collapses, shooting cracks, and concerning snowpack results were observed by backcountry travelers and professionals in the zone. This indicates that the snowpack was unhappy. The addition of liquid water over several days will continue to stress the snowpack before helping it in the long run. Don't overthink it. If it's raining instead of snowing, very dangerous conditions likely exist and you should exit avalanche terrain. Remember that any avalanche can be consequential this time of year due to generally low snow exposing so many rocks, holes, bushes, and open creeks.

Régions couvertes