Boletín de aludes

Flathead Range & Glacier NP

Flathead Avalanche Center
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Peligro de aludes

Sat
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

Slabs of newly-drifted snow will be today's primary avalanche hazard. These will be most widespread at upper elevations. Natural and triggered sluffs of loose surface snow can pose a threat on and below very steep slopes, particularly those receiving direct sun. Careful terrain selection can mean the difference between great riding and tumbling downhill in a slide. 

Problemas de aludes

  • Wind Slabs

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

    Near ridge lines, recents wind have transported snow into small drifts. Stick your hand or ski pole into suspected wind-blown snow to feel the texture. If it is stiffer or more consolidated snow, stop and reassess the terrain feature you are traveling in. As winds continue to build slabs, avoid convexities or gullies that harbor small pockets of dense snow. Today's winds may form pockets of stiff snow mid-slope that can be sensitive to a person's weight. 

    (4/8/2021) Convective snow showers left variable snow totals Thursday. Some areas saw up to 8" of new snow; others an angry inch.

  • Loose Wet

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

    Roller balls fanning down slope are a clear sign that the surface snow is losing strength and sluffs are a rising hazard. Natural sluffs of dense, moist snow are possible on steep slopes that recieve direct sun today. You can trigger loose snow avalanches on steep slopes that can be dangerous if you can't move out of the way, or they carry you into a terrain trap. Keep an eye on steep slopes above you that are getting direct sun. Move out from under these, or head to lower-angled slopes where the snow surface is still dry. 

Avalanche Discussion

Snow or wind, with the two factors not often coinciding Thursday. The weak system favored the Middle Fork corridor, with Tunnel Ridge and weather stations in John F. Stevens Canyon reporting 5 to 8 inches above 6000 feet. It looks like about 4 inches of new snow in Noisy Basin, 3 inches at Whitefish Mountain Resort, and zip in the northern Whitefish Range. The pattern is reversed for winds, with Tunnel Ridge and the Stevens Canyon stations recording light westerly winds with Moderate gusts, while Aeneas Ridge and Hornet showed averages near 20 and gusts of 40 to 50 mph.  Graupel made up much of the new snow, thanks to the convective nature of the showers. The primary weather influences today will be moderate ridgeline winds and partly sunny skies. 

In upper elevation terrain across the region, be on the lookout for pockets of dense, wind-blown snow. Give a second look to any patches of thick, drifted snow on a steep slope - how thick? How firm? What's downslope? The most dangerous combination will be slabs more than about 8 inches thick, more than four-fingers hard, and above a terrain trap. Today's ridgeline winds should keep the wind slab machine running, particularly in the Flathead Range. Freshly-formed slabs will be more sensitive to the weight of a rider or snowmachine. 

Without the wind, I don't expect the new snow to be cohesive enough to form slabs. Much of it fell as graupel or rimed particles. The loose snow may be a hazard in itself, however, thanks to today's direct sun and mild temperatures. Clumps of snow falling off rocks and trees can be triggers for suffs on steep slopes, particularly those receiving direct sun. There's not enough new snow for these to be dangerous across most of the region. The notable exceptions are the Middle Fork corridor and John F. Stevens Canyon. Sluffs can turn dangerous in confined terrain where you can't move out of the way. 

Pro tip: the tops of chutes and couloirs often harbor small pockets of wind slab. Climbing up into these can quickly turn into a fast, rough ride down, particularly if you have sharp, pointy things in your hands and on your feet. If you encounter dense, drifted snow on your ascent, stop; pushing it a few steps too far is a common theme in spring-time avalanche accidents in steep terrain.

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