Boletín de aludes

Flathead Range & Glacier NP

Flathead Avalanche Center
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Peligro de aludes

Sat
Alta montaña
1 · Débil
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

Plan your day to avoid traveling on or under steep, sun-baked slopes. Warm temperatures and sunshine can make the snow surface slide easily. Rollerballs and pinwheels should steer you toward terrain shaded from the sun. A small slide or cornice fall can cause a larger avalanche on buried weak layers.

Problemas de aludes

  • Loose Wet

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

    Yesterday (Thursday), warming and sunshine moistened surface snow enough to initiate Wet Loose avalanches. Increasing cloud cover in the afternoon limited the extent of warming and preserved dry snow on slopes that did not receive direct sunshine. Today, high pressure will continue to chip away at the snowpack. Natural and human-triggered avalanches are most likely on steep slopes that face the sun or near rock outcrops, which can soak up solar radiation and enhance warming in the surrounding snow. Large slopes can produce avalanches big enough to bury you. 

    Hone in on surface conditions as you travel today. Dry snow that becomes moist for the first time will develop this problem quickly. Slopes capped by a stout melt-freeze crust–or have already been worked over by Wet Loose activity– will be slower to transition. Moist surface snow can be identified by its capacity to form a snowball. Rollerballs and pinwheels indicate the snow surface is ready to slide and should steer you to slopes that tilt away from the sun. Plan your trip to avoid traveling on or under steep slopes that have been baking in the sun. 

    (1/8/2023)

    Small rollerballs due to the warming of the surface snow.

  • Persistent Slabs

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

    An avalanche that ran as recently as March 14th on Elk Mountain in southern Glacier National Park (photo above/to the right) reminds us that this problem still lurks among us. To date, avalanche activity on weak layers buried 2-4+ feet deep has occurred on mid- to upper-elevation slopes facing NW-NE-SE. 

    Recent avalanches in nearby or similar terrain are the most obvious way to identify this hazard. If this evidence is lacking, you can dig down to assess the snowpack structure. Steer around thin wind-scoured or rocky slopes where you suspect a weak layer is present. Choose slopes without convexities and away from overhead hazards to increase your safety margin. Remember that a small avalanche or cornice fall can step down to buried weak layers and produce a larger avalanche.

    (3/16/2023)

    A D2.5 avalanche failed sometime around March 14. This may have failed on a deeply buried weak layer.

    Photo: Adam Clark

Avalanche Discussion

In a winter characterized by cold temperatures, it's only fitting that the onset of warmer weather has been a slow and incremental process. Yesterday (Thursday), temperatures at mid-elevation weather stations approached 40 degrees Fahrenheit while upper elevations tickled freezing. Building clouds in the afternoon stunted this warming, and the resulting Wet Loose activity was modest. Today looks a couple degrees warmer across the board, with mostly clear skies. If the forecast verifies, anticipate similar activity as yesterday's melt-feeze crust breaks down on solar aspects and dry snow transitions to moist elsewhere.  

Yesterday, BNSF snow safety reported a natural, hard slab avalanche that failed on a buried weak layer during the last week. Continued–albeit few–natural and human-triggered avalanches are keeping this problem on the list. It is most evident in the Flathead Range, southern Glacier National Park, and the Whitefish Range north of WMR.

The southern end of the advisory area in the Swan Range was favored by snowfall earlier this week. In this area, you can anticipate any Wet Loose slides to entrain more snow and grow larger. In upper-elevation, leeward terrain, you can probably still find stubborn drifts of snow capable of producing an avalanche large enough to bury you.

FOFAC Event: March 30th, 2023– Whether you're chasing tan lines, big lines, or both, you'll learn something valuable from FAC Lead Forecaster Mark Dundas about spring avalanche problems, how they differ from winter problems, and how to manage them. We will also discuss current conditions and concerns (or lack thereof!) with our spring snowpack. Enjoy a cold brew from Bias Brewing and a scoop from Sweet Peaks Ice Cream.

The event is free and open to everyone. Begins at 6 pm.

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