Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Out of date — this forecast expired 5 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Continue to stick to slopes less than 35 degrees in areas where you don’t feel a supportable crust under your feet. That's most likely above roughly 6500 feet on shady aspects. In that terrain, it's still possible to trigger a large hard slab avalanche. Your safest option is to choose slopes where a thick, supportable crust blankets the surface.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Snowpit tests continue to show propagating results on weak layers that formed in late January. These weak layers sit below 3 to 6 feet of snow. An avalanche failing on one of these layers would be unsurvivable. 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, use safe travel protocols and only expose one person at a time.

    (3/9/2021) Hard slab avalanche broke on a convex, rocky slope, where winds had previously drifted snow.

Avalanche Discussion

The sensitivity of the late January weak layer, and potential destructive size of avalanches, is keeping us from dropping to low at all elevations. Dragons still lurk 3 to 6 feet below the surface. They are most worrisome on upper elevation, northerly facing slopes where no recent crust exists. What is making it less likely to trigger them is the depth that they are buried. It is difficult, but not impossible to collapse weak layers when they are buried this deep. The most likely trigger points are convex rollovers and rocky areas. Avoiding rollovers is straightforward. Look to see if a slope goes from less steep to steep in a short distance. Unfortunately, we don’t have X-ray vision, so seeing rocks buried under the snow is virtually impossible. I manage this by selecting simple looking slopes away from rocky outcroppings.

It is unlikely to trigger a hard persistent slab avalanche in areas where a supportable crust exists. This crust exists in most parts of the region up to 6500 feet and on solar aspects up above 7000 feet. In those areas, you will likely be able to travel in steep terrain with only having to manage loose snow hazards that will be small in size. That should be easy. If you feel the sun begin to heat you up and you start to see roller balls or wet loose avalanches coming from steep, rocky areas, watch for overhead hazards and move to shady aspects.

Lastly, cornices and glide cracks will be a concern for the remainder of the season. Both are more likely to fail during times of intense sun and/or warm temperatures, although both can fail spontaneously at times. It is best to just avoid being underneath both, or at least move quickly and one at a time if you need to. Cornice fall would be a likely trigger for a persistent slab avalanche.

Regions covered