Bollettino valanghe

Swan Range

Flathead Avalanche Center
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Pericolo valanghe

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Limite del bosco
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Non aggiornato — questo bollettino è scaduto 6 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Although the snowpack is stabilizing, isolated areas of unstable snow still exist. Provide yourself a margin for error if your travels take you above roughly 6500 feet. Steer around wind drifted pockets and ride one at a time to give yourself a safety net in areas where persistent weak layers are buried a foot or more below the surface. 

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    2

    The last reported persistent slab avalanches ran on the 13th.  Since then, a rain crust has capped the snowpack up to about 7000 feet. Weak layers of buried surface hoar are spotty at upper elevations where the 1/13 rain crust does not exist. It is unlikely, but not impossible, to find and collapse one of these weak layers that can cause an avalanche large enough to bury and injure you. Whumpfs and shooting cracks are your signs to seek out slopes less than roughly 35 degrees in steepness.

    (1/20/2021) Thin and rocky zones, like this one, are notorious for being likely trigger points for a rider. Choose concave and planar slopes where the snowpack is deeper and more uniform.

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Unlikely
    Dimensione
    1

    Ridgetop winds drifted recent snow into firm slabs on Tuesday. Though these slabs are proving to be unreactive, buy yourself an insurance policy by riding one at a time and steering around wind drifted snow below steep ridgelines and cross-loaded gullies. Pillowy looking surfaces and corniced ridgelines are your visual cues to identifying where you could have a problem.

    (1/18/2021) These cracked just below ridgelines above 6,000'

Avalanche Discussion

Mild temperatures have allowed the snowpack to stabilize since the 1/13 avalanche cycle. Today will be the 8th day since the last reported persistent slab avalanche. Yes, there is still lingering concern about weak layers buried in the snowpack. However, these weak layers of surface hoar are spottier above the elevation where the 1/13 rain crust lies. There is less of a concern in collapsing and triggering an avalanche on one of these weak layers where you feel the 1/13 rain crust, which is below roughly 7000 feet. If you decide to chase steep terrain at upper elevations, hedge your bets by choosing planar slopes where you can steer away from rocky outcroppings and avoid convex rollovers.

Strong winds on Tuesday blew whatever snow there was available to transport onto leeward aspects. Yesterday in the Flathead Range and Glacier National Park, Clancy and I stomped around on cornices and in wind loaded features and found mostly stable results. Due to a lack of observations, we still have the problem listed in the Swan Range where winds had more snow available to redistribute into slabs. Continue to use caution, especially in the Swan, near ridgelines where this problem lies. It will be most hazardous in extreme terrain where a small avalanche can have serious consequences. Remember, low danger does not mean no danger.

Regioni coperte