Bollettino valanghe

Swan Range

Flathead Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
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

A freezing rain crust blanketing the Swan Range makes triggering slab avalanches less of a concern below 6500 feet. There is uncertainty about how high up this crust extends, so stay leery of start zones at the highest elevations. Steer around convex rollovers and stick to planar slopes with clean runouts. Avoid isolated slabs of drifted snow on the leeward side of exposed ridgelines.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    There is a lingering concern for triggering a slab 1 to 2 feet thick in start zones above roughly 6500 feet. Below this elevation, it is unlikely, but not impossible to trigger a slab on buried weak layers thanks to a widespread freezing rain crust. If your decisions take you into steep terrain, choose slopes that are planar or convex. Select terrain with smooth, clean runouts and keep a partner in a safe location.

    (2/6/2022)

    A large avalanche in Clarence Creek, in the northern Whitefish Range. Possibly triggered by a snowmobile.

    Photo: Seth Carbonari

Avalanche Discussion

Buried weak layers of faceted crusts and surface hoar continue to show signs of instability. On Monday, a rider in the Flathead Range found propagating results with extended column tests. On Sunday, we received reports of audible collapses in the Flathead Range, as well as a large (2 of 5) avalanche that failed in the northern Whitefish Range. Other riders report no signs of instability. It appears these signs of instbaility are more common in areas where roughly a foot or more of snow sits above the weak layer in the Whitefish and Flathead Range. All of the reported human-triggered avalanches have occurred in the Whitefish Range.

A freezing rain crust up to 1 cm thick in the Swan Range is keeping the persistent slab problem at bay below 6500 feet. On Monday, Guy and I covered a lot of ground in the northern Swan looking for recent avalanches and testing buried weak layers. We found no noteworthy avalanches and felt a rain crust on all aspects and up to our highpoint of 6800 feet. Another rider found this rain crust on the west side of the range near Peters Ridge and up to the same elevation. The lingering concern is start zones above this elevation where there is uncertainty if this crust exists and where thicker slabs rest over weak snow.

Wind speeds up to 50 mph at the highest ridgelines still manage to find snow to blow around. You may find a shallow wind slab on the leeward side of exposed ridges. The more consequential scenario is if a small wind slab triggers a buried weak layer further down. Steer around heavily wind-loaded areas.

Regioni coperte