Boletín de aludes

Swan Range

Flathead Avalanche Center
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Peligro de aludes

Thu
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Until 8 inches or more new snow falls the danger will be MODERATE. It will rise quickly as soft slabs consolidate and loose dry sluffs have more snow to entrain on steep slopes. Track new totals and use small test slopes to see how well new snow is bonding to the low density snow, crusts, and weak facets underneath. Plan to avoid steep slopes as new snow accumulates and you see red flags like cracking and natural sluffing later in the day.

Problemas de aludes

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    New snowfall moves into the region by late morning. It will favor the Swan and northern Whitefish ranges. The danger of triggering slabs of new and drifted snow, as well as loose snow sluffs, will increase as 8 inches or more accumulates. Use small test slopes and hand pits to see how well new snow is bonding to underlying surfaces. Heavy snowfall rates, cracking in the new snow, and natural sluffing in very steep terrain are early warning signs that the danger is rising. Plan to avoid steep slopes if you are out late in the day. 

    (3/22/2021) Touchy storm slabs on Monday afternoon.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely
    Tamaño
    2–3

    Although it is unlikely, it is not impossible to trigger a very large hard slab avalanche failing 2 to 6 feet deep on shaded aspects above 6500 feet. Stick to slopes less than 35 degrees if you do not feel a supportable crust in hand pits under the new and recent snow. Avoid slopes near rocky outcrops, with variable snow cover, or with cornices overhead. Cornice fall or a smaller avalanche can be the trigger that sets off a destructive slide. The last reported avalanche failing on mid-winter weak layers was over a week ago. Though the potential consequences of being caught by surprise should keep the hazard in the back of your mind.

    (3/17/2021) The crown from a hard slab avalanche that's more than a few days old.

Avalanche Discussion

Small to large, natural and triggered, soft slabs and sluffs ran across the region starting Monday. The sun triggered many of these on northeast to east to southeast aspects on Tuesday. South and westerly slopes saw a round of wet loose avalanches Tuesday afternoon.

New snow begins by mid-Wednesday favoring the Swan and northern Whitefish ranges. It will fall on 4 to 12 inches of loose, low-density snow near and above treeline on shady aspects and on a melt-freeze crust on slopes that saw the most warming on Tuesday. Snowfall rates and ridgetop winds may be enough to thicken the new snow into slabs by Wednesday afternoon and into Thursday morning.

The snow from the past several days rests on a slick crust to about 6,500 feet, old wind slabs near and above treeline, or near surface facets. 

Deeper in the snowpack, mid-winter weak layers sit 2 to 6 feet deep. These layers have been unreactive for more than a week. A large cornice fall or smaller avalanche could trigger a hard slab on one of these layers. 

Glide cracks litter steep east to south to southwest-facing slopes above about 5,500 feet. New snow may make them difficult to see. It’s best to avoid slopes near and below them. 

Regiones cubiertas