Bollettino valanghe

Swan Range

Flathead Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

What the Saturday storm underdelivered in snowfall in the Swan Range, it made up for in windy conditions. Expect to encounter dangerous slabs of new and drifted snow downwind of ridges and in gulleys. This dense, thick snow is where you may trigger a slide large enough to bury or injure you. Seek out slopes sheltered from the wind for a safer, more enjoyable experience.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    Since Friday, consistent SW winds have transported low-density surface snow into slabs 1-2 feet thick on leeward slopes. While generally light, Saturday’s snowfall only added fuel to the fire. With 6 hours of gusts up to 80 mph at Mt Aeneas, you may find slabs further downslope than typical. Smooth mounded features below trees or rock outcroppings are evidence of a slab. Cracking around you or shooting away from you is direct feedback telling you to seek out terrain with slope angles less than roughly 30 degrees, or to seek out soft snow on slopes sheltered from the wind.

    (12/5/2021)

    Westerly winds have stripped snow from windward aspects and deposited this snow onto leeward (easterly) slopes. 

    Photo: Dundas

Avalanche Discussion

Snowfall associated with the current storm arrived later than forecast and generally less than expected, but enough to keep the danger elevated. Temperatures have warmed throughout the storm resulting in an upside-down snow surface. Winds have been the big driver in slab formation, with impressive wind speeds recorded at ridgeline weather stations, including a one-hour average wind speed of 60 mph and 6 hours with gusts above 80 mph at the Mt Aeneas wind sensor. On Saturday, parties in the Middle Fork and the Apgars reported windy, stormy conditions throughout the day. 

The winner of the snowfall derby was the Flattop SNOTEL in central Glacier Park, with 19 inches of snow and 2.3 inches of water. The Middle Fork corridor and Stevens Canyon picked up 8 to 10 inches with slightly less in the Whitefish Range. The usually reliable Swan Range recorded just a few inches this morning, where we replaced the Storm Slab problem with Wind Slab.

Pro Tip: Several weeks ago, a windstorm was responsible for bringing down numerous trees in Glacier Park and the Flathead Range. Traveling on the Sperry, Snyder Lake, Mt Brown trails in Glacier, and the Marion Lake trail is arduous due to the blowdown. We expect to find similar conditions on other trails when the coverage allows access.

We’re saddened to report an avalanche fatality Saturday in the Crystal Mountain area in Washington. This area had experienced hurricane-force, 100 mph, winds recently. You can find further details here.

Regioni coperte