Boletín de aludes

Flathead Range & Glacier NP

Flathead Avalanche Center
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Peligro de aludes

Sat
Alta montaña
2 · Moderado
Límite del bosque
1 · Débil
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

There is still a slim chance of triggering a large avalanche above 7000 feet in elevation. Rule out slopes where you dig down and do not find a thick crust capping buried weak layers. A skier was caught and carried in a small surface slide yesterday.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    2

    Recent observations indicate that buried weak layers were either destroyed by last week’s rain or capped by a stout crust up to 7300 feet. Above this elevation, conditions vary with aspect. Buried weak layers appear best preserved on wind-sheltered slopes that are shaded and face NW-NE-E. Cam and I were in the Flathead Range on Wednesday and found the 12/1 surface hoar layer intact and reactive in terrain that fits this description. As you climb above 7000 feet, take the time to dig down and verify what’s underneath your feet or machine. Choose slopes where you find a robust crust or default to lower-angle terrain.  Slabs failing on buried weak layers will break 2-3 deep and occur without warning. 

Avalanche Discussion

Yesterday (Thursday) in the Northern Swan Range, a skier was caught and carried by a small avalanche that broke in wind-loaded terrain at an upper elevation. Fortunately, they skied out of the slide without injury. You can find the full observation here. Last week’s snowfall favored this area, and the nearby weather station on Aeneas Ridge consistently clocks the highest winds in the advisory area. Although, on average, winds have been light with low amounts of blowing snow, I expect that there are other isolated terrain features out there that could produce similar slabs. A surface crust from Wednesday’s sunshine should prevent them from getting any thicker, though. Regardless, perk up a little before committing any extreme terrain, particularly the ridges, gullies, and other prominent features that channel the wind.

Low danger should not be confused with no danger. Here are some highlights for Low Danger from the North American Public Avalanche Danger Scale:

  • Generally safe avalanche conditions. Watch for unstable snow on isolated features.
  • Natural and human-triggered avalanches are unlikely.
  • Small avalanches in isolated areas or extreme terrain.

The lingering persistent slab problem is unlikely for northerly, upper-elevation slopes in all zones. However, the Flathead Range and Glacier National Park remain at Moderate danger due to the tendency for this terrain to produce larger and more consequential avalanches.

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