Avalanche forecast

Flathead Range & Glacier NP

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Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

You will find exceptions to an otherwise stable snowpack at upper elevations. As ridgetop winds increase this afternoon, watch for blowing snow and small drifts forming on exposed leeward slopes. It remains possible to trigger an avalanche on weak layers buried 1-2 feet deep if you climb to slopes without a stiff crust near the surface. Slopes with breakovers and rocky outcroppings are more suspect. Loose snow can sluff in steep, sheltered terrain. Use caution on slopes above terrain traps. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1

    Take heed of increasing winds today. They have limited snow to transport, and fresh wind slabs will likely be small. They may develop on isolated, favored slopes below saddles and in the tops of chutes. You may be able to trigger them where they form atop weak, sugary facets. They'll be denser than the snow in the trees or further downslope. Even small avalanches that knock you over on slopes above terrain traps can have magnified consequences.

    (1/26/2021) Cracking near the edges of isolated wind slabs. Marias Pass area.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2

    High elevation slopes that are not covered by the 1/13 crust? Steep slopes with rocky outcrops or rollovers? Grey stripes of buried surface hoar and faceted crusts about 1 to 2 feet down in your snow pit? This terrain is still suspect for the persistent slab problem. The crust reaches to about 6,500-7,000' depending on where you go. Where it's supportable, you and your machine will have a tough time collapsing the buried weak layers. Planar slopes with a deeper, uniform snowpack and those free of breakovers and rocky outcrops are the safest.

    (1/25/2021) High elevation slopes that are not covered by the 1/13 crust? Steep slopes with rocky outcrops or rollovers? This terrain is still suspect for the persistent slab problem.

Avalanche Discussion

The last avalanche cycle occurred during the Pineapple Express two weeks ago. It ended abruptly as a cold front and strong winds covered the surface with a widespread crust that reaches to around 7,000 feet. 

Since then, avy savy residents of the Flathead Valley have been focused on the snow surface. There are several reasons for that. First, we're all looking for better, less crusty riding. Second, we know that the safest slopes are those where the crust is preventing us from affecting pesky weak layers buried 1 to 2 feet deep. Finally, we're all so ready for new snow that we want to know what it may fall on, should the weather ever change significantly in our favor.

Observers across the region have been enjoying a bit of soft snow atop the crust. The best riding seems to be at middle elevations and on lower-angled, sheltered slopes where there are 1 to 8 inches of loose snow (example 1, example 2). The surface crust has been conspicuously missing in the highest terrain (example 1, example 2, example 3). That's a concern because layers of buried surface hoar and facets can still propagate in snowpack tests, and it's the crust that's preventing a rider from affecting these layers. Those in the know have been sticking to slopes where the crust is supportable, or to planar and concave slopes away from trigger points like convexities and rocky areas. 

In the near future, winds will increase throughout the day and may just have enough soft snow to drift into slabs above the weak surface. If you see blowing snow near ridgelines, pay attention. The slopes below may have stiffer drifts that can crack around you. The snow will be looser and sluffy on steep sheltered slopes. Even small avalanches are a problem if they carry you over a cliff or other terrain trap. Loose, faceted snow and hoar frost are widespread at the surface. If, in the long term, we get a stiff slab on top of these developing weak layers you can expect avalanche conditions to change for the worse. 

Regions covered