Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Wed
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Out of date — this forecast expired 6 years ago.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

The avalanche danger remains LOW, but don't let that lull you into complacency. It remains possible to trigger a slide on a weak layer buried 1-2' below the surface if your venture above roughly 7000', which is the upper extent of our surface crust. You're more likely to impact these layers on rollovers or near rock outcroppings. Planar slopes with a uniform snow depth and clean runouts are a wise choice.  Continue to carry rescue equipment and know how to use it. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2

    Where a thick hard crust exists, you or your machine will have difficulty affecting weak layers buried 1-2' deep. This crust is found on all aspects, but the top elevation varies from range to range and is roughly 6500-7000'.  Where the crust is not present or is thin and unsupportable, digging into the snowpack is the only way to identify this problem. You may find a grey stripe of surface hoar or faceted crusts that propagate in your snowpack tests. When in doubt, utilize the one constant in the avalanche triangle - terrain. Steer around areas where you are most likely to impact this layer: convexities where the snowpack is pulling apart, rocky areas where weak snow forms, or windswept slopes with thin snow cover. 

Avalanche Discussion

The past couple of weeks have been a bit nuts with weather patterns and avalanche danger rising and falling like the famous Coney Island Cyclone roller coaster. The Pineapple Express event arrived two weeks ago today, leaving behind a widespread crust up to 7000’, impressive wet debris piles (example 1, example 2), HIGH avalanche danger, and FAC issuing an Avalanche Warning. Since then, just the opposite. Our last decent shot of moisture occurred about nine days ago, the avalanche danger has been at LOW for six days, and Persistent Slab has been our only avalanche problem for the past five days.

Seasonal cool temperatures are keeping the thin layer of surface snow dry and light. Clancy was in the southern Whitefish Range yesterday and found near-surface facets, surface hoar, and loose snow above the 1/13 crust. He made a good point that we have 2 out of 3 ingredients for future slab avalanches, a bed surface, and a weak layer. With a possible change to a snowier pattern next week, the potential for slab development will increase.

In the northern Whitefish Range, Guy found a similar snow surface with 2-4 inches of light snow and weak layers capping the widespread crust. He noted well developed (2 cm) surface hoar on all aspects above 6000. The 1/12-13 storm resulted in numerous D2-D3 avalanches, although areas above 7,000' seemed to have not participated in this cycle.

Despite what seems to be a very dry January, the Flathead Basin is 94% average Snow Water Equivalent (SWE) with our mid-elevation snotel sites (Stahl Peak, Noisy Basin Flattop) on either side of 100% average. Interestingly, Flattop has more water than any snotel site in Montana or Idaho, with 29.4” in the snowpack. There’s no spilled milk to cry over here.

Regions covered