Bulletin d’avalanche

Seeley Lake

West Central Montana Avalanche Center
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Danger d’avalanche

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

Points saillants

Skiers and riders could trigger avalanches in the new and recent snow today. Look for signs of instability like shooting cracks, collapsing, and fresh avalanches, and be prepared to manage your sluff if you enter steep terrain. 

Although unlikely, you could also still trigger a large slab avalanche at upper elevations that fails on weak snow buried near the ground. You aren’t likely to see signs of instability before triggering such an avalanche. To avoid the problems, you can stick to low angle slopes.

Problèmes avalancheux

  • Storm Slabs

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

    Another 2 to 7 inches of new snow fell in the last 24 hours, favoring the Rattlesnake and Seeley Lake zones. The new snow is adding to the 6 to 12+ inches that fell since Saturday. Skiers and riders could trigger small avalanches in the recent snow at middle and upper elevations. Slabs will be larger and more sensitive in wind loaded areas at the highest elevations. On Wednesday, a skier had a close call in the Southern Bitterroot with a slab avalanche in the recent snow. We want to thank them for reporting the avalanche. 

    In some areas, the recent snow may rest on weak layers like surface hoar or crust facet layers and be more sensitive. 

    Small test slopes are an excellent tool for a problem like this. Look for shooting cracks, collapsing, and fresh avalanches. Avoid convexities and areas above terrain traps like gullies, streambeds, or road cuts. To avoid the problem, you can stick to slopes under 30 degrees in steepness.

    If the new snow remains loose and unconsolidated, small dry loose avalanches will be possible in steep terrain today, too. Be prepared to manage your sluff if you enter steeper terrain.

    (2/3/2024)

    A natural slab avalanche in the new snow on a wind loaded southeast aspect at 7900 ft in the Rattlesnake. It was 6-12 inches deep and around. 50 feet wide. 

    Photo: Arden Feldman

  • Persistent Slabs

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

    Although unlikely, skiers and riders could still trigger large persistent slab avalanches on upper elevation slopes. These avalanches could fail 2 to 4 feet deep on buried persistent weak layers near the ground. 

    The persistent slab problem becomes more widespread as you get higher in elevation. North aspects at the highest elevations have the most concerning snowpack structure, with a stiff slab above weak, sugary facets near the ground. However, a poor snowpack structure also exists on south aspects where the facets are still wet from last week’s warm temperatures and continue to propagate in snowpit tests. 

    The sensitivity of this problem has decreased, but the consequences of any avalanche triggered remain high. You aren't likely to experience signs of instability like collapsing or whumpfing as you travel through the mountains. Tracks on a slope are not indicators of stability - avalanches may be triggered after many riders have crossed a slope. 

    The best way to identify the problem is to dig in the snowpack and look for poor structure with a firm slab on top of weak, unconsolidated snow. If you find this, individual risk tolerance will dictate how steep of a slope you are willing to expose yourself to. However, if you want to avoid the problem, we recommend sticking to slopes less than 30 degrees in steepness. Short of that, you can reduce your risk by avoiding large avalanche paths and those with ugly consequences if you are caught in a slide.

    (1/20/2024)

    Looking up at the crown of a large human triggered persistent slab avalanche on an upper elevation east aspect in the Rattlesnake. 

Avalanche Discussion

Light snowfall with light west winds continued yesterday and last night, accumulating 2 to 7 inches of new snow across the region. The Rattlesnake and Seeley Lake zones were favored in this latest round. Today, the light snowfall and light winds will continue through the morning and accumulate 1 to 3 inches. High pressure will move in for the weekend, bringing generally drier conditions. 

Avalanches in the new and recent snow are the primary concern for today. Weak layers near the ground are gaining strength, and the likelihood of triggering a larger persistent slab avalanche continues to decrease. At upper elevations, observers continue to find poor snowpack structures with propagating snowpit test results. However, on the west side of the Seeley Lake zone yesterday, we found a much more well-bonded snowpack. The facets near the ground had rounded and gained significant strength. The higher snowfall amounts in this part of the zone have contributed to the healing process. Nevertheless, the possibility of triggering a persistent slab remains on the table, especially in the highest, north-facing terrain of other areas with shallower snowpacks. Remember, unlikely does not mean impossible, and the consequences remain high. 

Choosing to enter avalanche terrain with a low likelihood, high consequence problem like this is a matter of risk tolerance. If you find a slab over persistent weak layers and want to avoid the problem entirely, stick to slopes less than 30 degrees in steepness. If you decide to step out to steeper terrain, remember to use good travel practices, like riding one at a time. 

Please submit an observation to let us know what you see in the mountains today, especially regarding new snow totals and any signs of instability. 

Ski and ride safe.

Régions couvertes