Avalanche forecast

Swan Range

Flathead Avalanche Center
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Avalanche danger

Thu
Alpine
1 · Low
Treeline
1 · Low
Below
1 · Low
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Warm temperatures may wet the snow surface this afternoon. What starts as a small rollerball today could entrain enough snow to injure you in consequential terrain. Avoid tangling with a loose wet avalanche by seeking out shaded slopes during the heat of the day. A weak layer buried 2 to 3 feet deep may still exist at the highest elevations in the forecast region.

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    A strong temperature inversion will lead to above-freezing temperatures above 6000 feet. Warm temperatures and solar radiation may warm the snow surface enough for the grains to loose cohesion and sluff down steep slopes. If you feel the sun on your back, or see rollerballs begin to pinwheel down the mountain, be ready to move to shaded aspects, or reduce your slope angles. Slides could grow large enough to injure a human.

     

    (4/23/2023)

    Photo from 2022-23 season. Fields of rollerballs from recent warming of new snow. Rollerballs are a sign of an impending wet loose problem. Steep, sunny, rocky areas are common zones for these to start in. 

    Photo: md

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2

    Persistent weak layers buried in the middle of the snowpack and near the ground continue to gain strength. Triggering a large slab avalanche on one of these layers is unlikely but not impossible. If you climb well above 6500 feet, probe around to feel for a thick crust beneath roughly 1 to 2 feet of snow. A person's weight is less likely to collapse a buried weak layer where this crust is supportable and thick. IF you are able to easily break through this crust with your foot, or you climb high enough and don't find it, reduce your slope angles to less than 35 degrees. If your decisions take you into avalanche prone terrain, expose only one rider at a time while keeping a spotter in a safe location. 

    (12/4/2023)

    This layer of surface hoar may be preserved underneath a crust at the highest elevations in the forecast area. A thin grey stripe is a visual indicator it exists. 

    Photo: Cam Johnson

Avalanche Discussion

Tuesday's mild temperatures will warm more today. Freezing levels may climb up to 10,000 feet. If you are out today and feel the sun coming out, move off of and out from under steep, southerly-facing slopes. Rollerballs coming out of steep, rocky terrain and snow falling out of trees are early signs of a wet loose problem. Point-release avalanche will likely be small in size and will need very steep terrain. 

Above 7500 feet we have limited information about the 12/7 crust and the buried persistent weak layers buried further down in the snowpack. If your plan involves going into this type of upper-elevation terrain, then probe regularly and/ or dig plenty of holes in the snow and track the hardness of this layer. If you notice this crust transition from a 2 to 4-inch thick supportable layer, to a thin and breakable crust, then evaluate where on the slope you are.  A thin and breakable crust, or no crust, with dry snow below, means you could still find a weak layer of surface hoar or facets. 

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