Bulletin d’avalanche

Banner Summit

Sawtooth Avalanche Center
Voir sur la carte

Danger d’avalanche

Tue
Alpin
2 · Modéré
Limite forestière
2 · Modéré
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

Triggering a 1-3 foot thick avalanche is most likely on slopes where the wind has formed drifts or stiffened the snow surface. Triggering avalanches in areas sheltered from the wind is unlikely but not entirely out of the question. There's a chance you could trigger avalanches  remotely—from flat terrain below, above, and to the sides of steep slopes.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1.5–2

    What and where is it: You could trigger soft and stiff, 1-3 foot thick slabs where wind formed drifts or stiffened the snow surface, most likely near ridgelines over about 8500'. Triggering an avalanche is far less likely—but not out of the question—on steep slopes that are sheltered from the wind. Where slabs exist, they rest above a variety of weak layers (facets, crust + facet combinations, and possibly surface hoar). The widespread nature of the weak layers means avalanches are possible on many aspects. 

    How can you recognize it: Snowpack cracking (photo), and collapsing or whumphing, are clear signs of unstable conditions. Watch for snow pillows, dunes, and ripples (photo), and feel for stiff snow under your feet or sled. These are signs the wind has been at work transporting snow. Assume the weak layers exist on most slopes.    

    How can you manage it: You can avoid steep, wind-loaded slopes to significantly reduce your chances of triggering an avalanche. Persistent Slabs can release in surprising ways, break wider than expected, and release above or hundreds of feet away from where they are triggered. Remotely triggering an avalanche from flat terrain below steep slopes remains possible. Keep a close eye on your partner and the terrain that's above you.

    Additional Discussion: You may find fresh, soft, thin wind slabs near exposed ridgelines. The slabs could overlie graupel or other weak snow at the old-new snow interface, making them easy to trigger. While these slides should not be large enough to bury people, they could carry you where to don't want to go or trigger the larger, more dangerous Persistent Slab avalanches described above. 

    (12/21/2024) Skier-triggered avalanche near 9800' on a NE aspect in the northern Boulder Mtns.

Avalanche Discussion

Throughout the forecast area, we're teetering between MODERATE and CONSIDERABLE danger. The Banner Summit zone has fewer wind-loaded slopes than other zones, pointing towards MODERATE danger today. Whether the danger is MODERATE or CONSIDERABLE, you're far more likely to trigger slabs in exposed areas versus in terrain sheltered from the wind. Don't trust wind-loaded starting zones or the runouts of large, wind-loaded avalanche paths (due to the lingering chance of remotely triggering avalanches from below). Some key recent observations and information:

  • Yesterday, Zach experienced several snowpack collapses—some in excess of 100 feet—in wind-loaded terrain in the Headwaters of the Salmon/Frenchman Ck area.  View his observation here.
  • Saturday, a group reported a human-triggered avalanche in wind-affected terrain near 9800 feet on a NE aspect in the northern Boulder Mtns (Galena Summit & Eastern Mtns zone).
  • Saturday, professionals reported a booming snowpack collapse that sounded like a shotgun near Copper Mountain in the Banner Summit zone (NE aspect near 8800 feet).

If you choose to play on or under steep slopes, avoiding terrain traps and large, consequential avalanche paths will reduce the risk of bad outcomes.

Régions couvertes