Bulletin d’avalanche

Northwest Mountains

Crested Butte Avalanche Center
Voir sur la carte

Danger d’avalanche

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

Points saillants

Early this week, a northwest wind event eroded the snow in many places while leaving behind small slabs in a few places. The most common location to find these lingering slabs will be in cross-loaded gullies and below wind-loaded rolls in the terrain. They may also exist on the lee sides of some ridgelines. As new snow starts to accumulate this afternoon, a new round of small wind slabs will begin forming at upper elevations. The softest snow surface, and probably the best skiing and riding, can be found in wind-sheltered locations with no slab avalanche concerns. 

Problèmes avalancheux

  • Persistent Slabs

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

    During the first half of the week, a northwest wind event combined with an average of 4" to 12" of new snow and created slabs on a few wind-affected terrain features. These slabs have mostly been found in concave terrain features such as cross-loaded gullies or rollovers in the terrain. These slabs could also be found below the lee sides of some ridgelines. More commonly, the snow was blown away and eroded, leaving these lingering slabs less common across the terrain and more isolated in their big-picture distribution. 

    In very  isolated areas, an avalanche could release several feet deep on weak layers near the ground. These areas would have need to retain the full-season snowpack without that snowpack having been removed by the widespread avalanche cycle that occurred in late November. 

    You can see the outline of a slab that tried to displace but didn't move far downhill. This is a cross-loaded terrain feater at 11,500ft. Note the wind-eroded snow by the skier and smoother wind-loaded snow in front of the skier. 

  • Wind Slabs

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

    Later this afternoon, small wind slabs will begin to form at upper elevations after a few inches of snow accumulates. Given the meager snow forecast, any slabs that form are expected to be small and relatively easy to manage. 

    An example of a small wind slab that released below Schuylkill Ridge earlier this week. 

Avalanche Discussion

Snow accumulation in the Gunnison River Basin has basically flatlined since November 28th. Click here to see the graph. This extended drought has greatly reduced concerns for avalanche activity involving the Thanksgiving Slab or Gizzard Blizzard. We have now transitioned into a period where each small storm we receive creates a new round of wind-related slabs over the old, weak snow surface. The last NW wind event did more wind erosion than slab formation. The slabs that are left over from this event are covered by the current persistent slab avalanche problem. These slabs formed over small near-surface facets and, in some cases, on large depth hoars where that slab developed on an old bed surface from the avalanche activity back in November.  An example of some of these slabs can be seen in this observation from yesterday. 

Looking ahead, we can expect a new round of wind slabs to begin forming on Friday afternoon with the arrival of our next small storm. Forecasted snow totals are meager,  and the old snow volume available for transport is also low. So, any new wind slabs that form are expected to be small unless we luck out and exceed the forecasted snow amounts. After each round of new snow and wind, the distribution of old slabs will become hard to identify. By the end of the weekend, we could see a few avalanches break deeper than expected in this layered cake of thin slabs stacking on top of each other. 

Régions couvertes