Bulletin d’avalanche

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Danger d’avalanche

Sun
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré 4 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Friday night brought in more snow and gusty winds out of the north, with storm totals ranging from 8-15" in the last 24 hours. Human triggered avalanches are very likely in terrain greater than 35 degrees above treeline. Stay safe today by avoiding steep and wind effected terrain. The best and safest riding will be in timbered locations protected from the wind.

Problèmes avalancheux

  • Storm Slabs

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

    The new snow will be resting on a variety of crusts and wind scoured surfaces that my bond poorly. General wind direction has transitioned the last 48 hours from southwest, to west and now coming out of the north and east. All terrain that is open enough to catch some wind will have snow that is drifted and slabby. Steep chutes and terrain directly below ridgelines should be avoided at Treeline and above today. New snow at lower elevations will be less likely to avalanche as the temperatures were warm early in the storm cycle.

  • Persistent Slabs

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

    Two issues exist here. There is a layer of buried surface hoar at Treeline and above  that is unlikely to be triggered at this time. The second issue is the crust layers in the upper snowpack that are layered with weak, sugary snow. These surfaces were not a concern Thursday, but as we load them and build a fresh slab above them they will become a problem that may stick around for awhile.

Avalanche Discussion

The generally stable weather we enjoyed for the past couple weeks has given way to significant weather change with Pacific moisture entering the region, followed by an Arctic cold front that moved in last night. Thursday night 5-8 inches of heavy snow fell on top of a somewhat complex upper snowpack consisting of crusts and poorly bonded layers that have shown a propensity to fail, but not propagate. It’s hard to predict exactly how the upper snowpack will react to the new load, but anytime we get this much precipitation avalanche danger rises. The Lucky Friday Crust remains stout, especially on southern aspects, with poorly bonded snow on top. Throw on 8” of new snow load and we have the ingredients for avalanches: bed surface, weak layer, and load. At least the snow is coming in “right side up”: the density and characteristics of the snow will change from warm wet snow produced early in the storm to cold light snow as the temperature drops tonight.

Until the weather settles, it is important to proceed with caution. Dial back your terrain choices until the snowpack settles and we get a feel for the new dynamics at play.

Régions couvertes