Lawinenlagebericht

Flathead Range & Glacier NP

Flathead Avalanche Center
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Lawinengefahr

Wed
Hochgebirge
2 · Mässig
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 5 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

It is possible to trigger a very large hard slab avalanche in areas where you do not feel a crust under your skis or machine. As you climb higher, pay closer attention because the crust thins with elevation. Where no crust exists, stick to slopes less than 35 degrees with no overhead hazard.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    Snowpit tests continue to show propagating results on weak layers that formed in late January. These weak layers sits below 3 to 6 feet of snow. An avalanche failing on one of these layers would be unsurvivable if triggered. Stick to slopes less than 35 degrees if you do not feel a supportable crust under your feet. If you do feel a supportable crust, and choose to seek out steeper terrain, expose one person at a time. Manage the terrain so you have eyes on your partner at all times.

    (3/4/2021) A very large Persistent Slab avalanche on an SW aspect in southern Glacier Park. Warm temperatures and solar radiation triggered this slide.

Avalanche Discussion

Unseasonably warm temperatures last week followed by cold temperatures the past two days have helped lock the snowpack in place, in most locations. The areas of most concern are at upper elevations where a melt-freeze crust or freezing rain crust does not exist. In these areas, it is still possible to trigger a hard slab avalanche failing on persistent weak layers from late January. The most likely areas where you could collapse these layers will be on convex rollovers and rocky outcroppings where they are more stressed and closer to the surface. Stick to simple-looking slopes with clean runouts. Stay out from underneath slopes that harbor glide cracks or large cornices. 

Low probability, high consequence. It is a lot like the lethal game of Russian Roulette where the player places a single round into a six-shooter. Last week during warm temperatures and solar radiation there were three bullets in the six-shooter. Triggering a lethal avalanche was more likely. Thanks to cold temperatures re-freezing the snow surface, we are down to one bullet. This can make playing the game more inviting since the likelihood is less; however, the consequences remain the same. Stack the odds in your favor by sticking to terrain that has a supportable crust, or keep slope angles less than 35 degrees. If you are seeking out steep terrain that faces south, plan to be off these slopes if you feel the crust begin to break down with solar radiation.

If we are lucky, we may see an inch or two in the southern end of our forecast region. Expect any new snow to sluff easily on top of recently formed crusts. These will likely only be hazardous in consequential terrain.

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