Boletín de aludes

Flathead Range & Glacier NP

Flathead Avalanche Center
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Peligro de aludes

Fri
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
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

It is still possible for you to trigger a large avalanche on a buried weak layer. Sunshine and warm temperatures may cause wet snow to slide easily. Rollerballs and pinwheels are clues that it is time to retreat from sun-baked slopes. 

Problemas de aludes

  • Loose Wet

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

    Today will be the warmest day since Saturday's snowfall, with the potential for temperatures nearing 40 degrees Fahrenheit at upper elevations. Observations this week indicated only minimal wet-loose activity and thin melt-freeze crusts. Abundant sun and warm temperatures have the potential to quickly break down surface crusts and transition dry snow to wet on aspects SE-S-NW. Slides will be largest in areas favored by Saturday's snowfall, like the Northern Flathead Range. 

    Rollerballs and pinwheels are indicators that the surface snow has become wet and is ready to slide. This evidence should be your cue to seek out slopes shaded from the sun or make an earlier exit. Plan your day to avoid travel on or under steep, sun-baked slopes. 

    (12/28/2022)

    Dirty debris signifies that this slide ran on the ground removing the seasonal snow cover. This slide looks to be a wet loose. However, there may be a crown at the top of the slide.

    Photo: Mark Dundas

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1.5–2.5

    On Sunday, observations reported natural and human-triggered slides large enough to bury a rider. These avalanches failed on a weak layer of facets buried by Saturday's storm snow, with crown depths approaching 3 feet in wind-loaded areas. Persistent Slabs can break well above you, wider than expected, and wrap around terrain features (as depicted above/right). You may be able to trigger avalanches remotely—from gentler terrain below, above, and to the sides of steep slopes. Recent avalanches, shooting cracks, and audible collapses are bulls-eye data for this problem and should direct you toward lower-angle slopes.

     

    (4/2/2023)

    This avalanche was triggered from the ridgeline close to where my partner (Tom Whipple) is standing in this photo. This part of the slope measured 32 degrees in steepness and was on a ridgeline. 

    Photo: Cam

Avalanche Discussion

Safe and enjoyable riding might require a bit of a two-step today. As the snow becomes warm and wet on slopes tilted toward the sun, you’ll be inclined to seek out shadier aspects. When doing so, keep your head up for instabilities related to wind-drifted snow and buried weak layers. 

Relatively cold temperatures have preserved Saturday’s snowfall, and Southwesterly winds increased to threshold speeds for transporting snow yesterday afternoon. This combination may build slabs of wind-drifted snow along ridgelines, saddles, and midslope ribs and gullies. These will generally be small in size in the Swan and Whitefish Ranges. Steer around steep slopes with a scalloped surface or dune-shaped features when accessing steep, shaded slopes. 

In the Flathead Range and southern Glacier National Park, where up to a foot of snow fell last weekend, wind-drifted snow will fall onto a weak structure that produced large avalanches and surprised multiple parties Sunday. Dig a pit to determine whether this weak structure is present and use snowpack tests or small inconsequential slopes to assess its sensitivity. Fall back to low-angle terrain for the greatest safety margin. 

Have feedback for us? Let us know how we can serve you better. Special thanks to Friends of FAC for creating this survey: link here.

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

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