Boletín de aludes

Flathead Range & Glacier NP

Flathead Avalanche Center
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Peligro de aludes

Sat
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 2 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Danger will rise today due to rapid warming and intense sunshine. Large avalanches may occur naturally and run long distances. Move off of and out from under steep slopes during the heat of the day. 

Problemas de aludes

  • Persistent Slabs

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

    Warming temperatures will stress buried weak layers and could result in very large avalanches that break 2-4 feet below the surface. Several faceted crusts have been documented on NW-N-SE aspects above 5000'.  These layers are not always reactive in stability tests and can give the impression of being benign or stable. The deepest layers consist of rounding facets near a stout crust formed in early February. During a wind-loading event two weeks ago, this layer produced a cycle of very large avalanches in the Flathead Range.

    Give steep, shaded slopes a wide margin.  Recognize that small surface slides or cornice falls have the potential to trigger more destructive avalanches on buried weak layers. 

    (3/7/2024)

    This is a view of a small section of the crown of a large hard slab avalanche triggered by snowfall and intense wind loading. This slide likely failed on a layer of buried facets above the early February crust. 

    Photo: Mark Dundas

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–3

    Today starts a bit warmer and is expected to be clearer than yesterday.  A series of crusts may delay the onset or limit the extent of wet loose activity on solar aspects. Slopes sheltered from the sun may still have 4-12 inches of dry snow that will rapidly transition to wet. Rollerballs and snow falling from the trees are early signs of impending wet loose activity.

    Small point releases can entrain significant amounts of snow and travel further than expected, especially when sliding on one of several crusts in the snowpack. While slow-moving, an avalanche of this nature will be hard to escape and could easily push you over cliffs or into trees. Limit your risk by choosing slopes that are more shaded and/or less steep, free from overhead hazards.

    (2/6/2024)

    Wet loose avalanches will be easy to trigger and may occur naturally on steep rocky slopes.

    Photo: Michael Reavis

  • Cornices

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

    Since mid-February, prevailing southwesterly winds have built large, overhanging cornices on slopes facing NW-N-E-SE. These giants will weaken during today's sun and warmth and can fail naturally or when approached by a rider. They often break much further back than you would expect.

    Whether you're on it or below it, a tumbling chuck of cornice is enough to ruin your day.  Cornice fall can also trigger large and destructive avalanches on buried weak layers, as described above in the Persistent Slab problem. Do not linger on or under slopes with cornice looming overhead. Give them a wide berth as you navigate ridgelines. 

    (3/7/2024)

    Cornices like these will begin to weaken, crack, and fall due to warming temperatures.  Do not linger on or under slopes with cornice looming overhead. Give them a wide berth as you navigate ridgelines. 

Avalanche Discussion

Yesterday's wet loose action was more fizzle than sizzle. Today should bring on the heat in earnest, though crusts from previous warming could still limit the extent of today’s activity. Our last prolonged warming occurred late January into early February and resulted in a widespread avalanche cycle on a buried weak layer. Very large hard slabs failed early during the warming, followed by a cycle of wet slabs. That same event yielded the stout 2/3 crust.

Since then, a layer of facets near the 2/3 crust has produced sporadic action in our advisory area and beyond. It has also caused fatalities North, West, and South of our region. As we enter a period of prolonged warming, the stage is set for increased activity on buried weak layers, in addition to typical springtime problems like wet loose and cornice fall.

Avalanche Canada is painted red today, and all zones are expected to reach HIGH avalanche danger this weekend. Large human-triggered avalanches occurred near Fernie this week. Areas North have received more snow recently, and buried weak layers have been generally more reactive from the onset. Still, the slew of accidents and fatalities across the northwest US and Canada are a good reason to default to conservative terrain choices. Today, make it less about riding big terrain and more about laying in that base tan.

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