Boletín de aludes

Flathead Range & Glacier NP

Flathead Avalanche Center
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Peligro de aludes

Sat
Alta montaña
1 · Débil
Límite del bosque
1 · Débil
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 6 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Continue to practice safe travel protocols during periods of low danger. Above 7000 feet, avoid trigger points, like rocky outcroppings and convex rolls. These spots are where you might release avalanches that break a foot or so deep on otherwise unreactive weak layers. Give yourself a safety net by only exposing one person at a time if traveling in avalanche terrain. Use this same tactic if you find small pockets of wind drifted snow below ridgelines and in cross-loaded terrain features.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    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, or turn the corner and ride on the supportable crust. 

    (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.

Avalanche Discussion

On Thursday, Clancy and a strong volunteer went into the Flathead Range to get a sense of what is happening in upper elevation start zones and hunt for buried surface hoar. They found the most recent rain crust to stretch up to 7000 feet, with pockets of it reaching as high as 7700’. On a sheltered northeast slope, they were able to find an unreactive layer of buried surface hoar roughly a foot below the surface. This further supports that this layer is gaining strength and making triggering it unlikely. They chose to ride steep terrain one at a time where the crust existed (observation).

Other observations came in Thursday of good, supportable riding conditions in the southern Whitefish Range. Here riders took advantage of choosing to ski steep terrain on aspects where the rain crust is found, and still supportable (observation 1, observation 2). This is a good tactic right now for finding the safest, and best riding conditions. The biggest concern is navigating breakable crust getting to and from areas to ride. We have heard of, and taken aggressive falls ourselves, due to catching edges in this crust. Proceed with caution.

Thursday was the first day since December 14th that we rated the avalanche hazard as low. We made it through more than a month of tricky avalanche conditions. Large natural avalanche cycles and persistent weak layers tested our patience and skills. It appears that mild weather will continue for at least the next week. We can expect the avalanche hazard to remain low until there is a change in the weather pattern. Don’t let your guard down during this time. If you choose to brave the frozen layer, keep your eyes open and look for obvious clues of instability. Steering around isolated wind slabs that linger below ridgelines, and digging holes in the snow to look for a buried surface hoar can help keep you out of harm's way.

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