Boletín de aludes

Swan Range

Flathead Avalanche Center
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Peligro de aludes

Tue
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

A couple of inches of recent snow and moderate winds formed drifts downwind of ridgelines and saddles. Pockets of wind-drifted snow will be small and easy to manage. Stear around dune-shaped drifts while seeking out soft snow sheltered from the wind.  

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–1.5

    Look for and steer around signs of obvious drifting near ridgelines and on cross-loaded gullies further downslope. Pillowy-looking surfaces or surfaces with a textured appearance are visual clues of a Wind Slab. Slabs of drifted snow should be harmless in size by themselves, though they could be consequential if caught above a cliff or stand of trees. Slopes sheltered from the wind will hold safer and better riding conditions. 

    (4/2/2023)

    Isolated wind slab found just below a ridgeline in the northern Whitefish Range. 

Avalanche Discussion

A recent storm divided our forecast area into two different teams. Team Flathead/Glacier National Park led the charge with roughly 12 inches of storm snow. Team Whitefish and Swan Range came in last with roughly 2 to 4 inches of snow. Unfortunately, team Flathead/Glacier National Park also took the lead yesterday (Sunday) with the most human-triggered avalanches. Two avalanches resulted in people getting caught and carried in large slides, and another avalanche resulted in a close call. The amount of recent snow plays a key role in the avalanche problems and variability among the forecast zone.

Flathead Range/Glacier National Park

We transition to a Persistent Slab Problem in the Flathead Range/Glacier National Park due to travel advice and the grain type that avalanches are failing on. More snow fell, which resulted in avalanches failing in wind-sheltered and wind-loaded terrain. Although slabs are relatively soft, they are behaving more like a Persistent Slab than your run-of-the-mill storm snow avalanche problem. For example, my party triggered an avalanche that propagated 600 feet wide, wrapped around a sharp ridgeline, and put debris down into two separate drainages (observation). Other parties remotely triggered avalanches, with one slide stepping down to a deeper buried weak layer (observation). 

We are uncertain how long this problem may linger, but we suspect avalanches will remain reactive to the weight of a person for the near future. 

Whitefish Range/Swan Range

Generally speaking, not enough snow fell to form a slab in the Whitefish Range and the Swan Range. However, sustained winds drifted the few inches of snow into small slabs on the downwind side of ridges and gullies. Slabs of drifted snow may still be reactive to the weight of a rider, but likely small in size and confined to wind-drifted features. I would expect to see slides similar to the ones found in this observation. These should be easy to manage by giving them a wide berth and by sticking to wind-sheltered slopes. 

We received no observations from the Swan Range, giving us a slightly higher degree of uncertainty there. IF you find more snow than expected, dial back your terrain choices and give steep slopes a wider margin for error. 

FAC will issue daily forecasts through Easter Sunday, April 9. Following this, we will give snowpack updates several times a week through April if conditions dictate. 

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