Boletín de aludes

Flathead Range & Glacier NP

Flathead Avalanche Center
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Peligro de aludes

Sun
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

Strong winds will drift new snow into slabs on leeward aspects above roughly 5000 feet. Pay attention to accumulating precipitation today and use small, inconsequential, wind-drifted features to test how reactive slabs will be. Stick to slopes sheltered from the wind or keep slope angles less than 35 degrees if you get shooting cracks or the new snow has a hard-over-soft feel to it.

Problemas de aludes

  • Wind Slabs

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

    Expect new and drifting snow to build firm slabs up to 12 inches thick on leeward aspects near ridgelines, as well as cross-loaded terrain features further downslope. Signs of drifting snow and pillowy surfaces are your clues to seek wind-sheltered terrain. While fresh wind slabs today should be relatively small, they could get you in trouble if they drag you into a terrain trap or step down to a thicker, harder wind slab that formed on Thursday and Friday. Identify and avoid terrain features that are actively wind loading.

    (4/9/2021) Small wind slab triggered on a test slope. Utilizing small, inconsequential terrain features, like this one, is a good tool to test how reactive slabs are.

Avalanche Discussion

In order to get a grasp on today’s hazards, we need to step back and look at how the storm played out on Thursday. The storm on Thursday left varying snow totals throughout the region. The Lake McDonald area of Glacier National Park saw an inch or two of new snow, while areas in the Flathead Range saw roughly 6 to 8 inches (observation). One observer in the Swan Range found roughly 4 inches of new snow at 6000 feet and the Whitefish Range appears to have mostly gotten missed by precipitation. This variability stresses the importance of periodically getting off your machine, or off the skin track, to dig down to see how much snow fell in the basin you are traveling in. While snow totals did vary, strong southwest winds were fairly consistent across the region and drifted this snow into slabs on leeward-facing slopes.

Today we are expecting anywhere from 3 to 6 inches of new snow that will get transported easily by strong winds. This wind-blown snow will form reactive slabs that will rest over a stubborn, older slabs from Thursday and Friday. The new slabs in the Flathead Range and parts of the Swan Range will be thicker and can produce an avalanche large enough to bury a person. Slabs will be thinner and less dangerous in the Whitefish Range.  Signs of wind drifted snow will be obvious today. Identify and avoid where the wind is actively loading certain terrain features. If you find more than 8 inches of new snow that has a slabby feel to it, dial back your slope angles or go to aspects that are sheltered from the wind.

Despite cooling temperatures, it is best practice to stay out from underneath glide cracks and cornices. These spring hazards are challenging to predict and can still fail during times of below-freezing temperatures. Give the edge of ridgelines an increased buffer zone, especially if visibility is obscured by blowing snow and clouds.

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