Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Dangerous avalanche conditions exist where stiff storm snow rests on weak layers. The hazard is highest on wind-loaded slopes, where you could likely trigger a 1-2 foot thick slab avalanche. Choose low-angle terrain free of overhead hazards for a safer experience.  

Due to complex conditions and expected weekend traffic, we have issued a SPECIAL AVALANCHE BULLETIN  through Sunday, February 2nd.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    The Friday/Saturday storm deposited 6-12 inches of snow onto widespread weak snow and crusts. Moderate to strong south-to-west winds formed dense 1-2 foot thick slabs and added to cornices. Slabs will increase in thickness and distribution as you gain elevation. Riders can trigger an avalanche at the interface of the new and old surface in both sheltered terrain and on slopes open to the wind. These will be more likely and dangerous where the new snow has been stiffened and slopes are steeper than roughly 35 degrees. 

    Due to the underlying weak snow, this problem is not straightforward to manage. You could trigger slides remotely—from flat terrain below, above, and to the sides of steep slopes. They may break surprisingly wide and wrap around terrain features.

    The easiest way to manage this problem is to stick to low-angle terrain without overhead hazards. Slabs will be particularly sensitive on rollovers or convexities. Monitor the cohesiveness of the surface snow and look for signs of a sensitive slab, such as cracking or collapsing.

    (2/1/2025)

    A soft slab avalanche on a wind-loaded rollover or convexity. WMR ski patrol triggered this slide with explosives. 

    Photo: Mark Dundas

Avalanche Discussion

The storm that ended our dry January deposited around one inch of water (SWE) and 6-12 inches of snow across the forecast area. Wind stations reported moderate to strong winds, with observers noting significant wind transport (Image) and reactive cornices (Image).

Our current storm slab problem behaves more like a persistent slab problem due to the underlying weak layers. Storm slabs normally heal in 2-3 days, but instabilities tend to linger when they rest on persistent weak layers. Expect unusual behavior in the surface snow in areas with cohesive new and wind-blown snow. We will likely transition to a persistent slab problem in the coming days.

Observations were limited for a powder Saturday, especially from upper elevations where the wind blew strongest and the danger is more widespread. WMR patrol had good results with explosives in wind-loaded terrain (Image, Image), where the new snow had been stiffened into a dense 1-finger slab. I traveled in multiple aspects of the WMR side country; both wind-sheltered and on slopes open to the wind. I observed intentionally triggered slides on slopes steeper than 35 degrees in sheltered locations and impressive shooting cracks failing on the old/new interface.  The slab in these areas was very soft (4-finger) and did not propagate widely. Other sheltered slopes harbored cohesionless snow that was not a concern. 

Parties in the Flathead Range and the Swan Range did not see any signs of instability, such as cracking, collapsing, or recent avalanches. They noted wind transport and enjoyed soft, cohesionless snow in locations sheltered from the wind. An observation from Red Meadow in the Whitefish Range noted small storm slabs triggered by tree bombs and riders. 

 

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