Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
1 · Low
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Out of date — this forecast expired 6 months ago. You’re viewing past conditions, not the current bulletin.

Highlights

Impressive winds are loading buried weak layers and building sensitive drifts. For safer riding, choose low-angle and wind-sheltered slopes, free from overhead hazards. Small surface slides can trigger a larger and more destructive avalanche on buried weak layers. 

Avalanche problems

  • Persistent Slabs

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

    Large and destructive avalanches have run naturally within the last 3 days. Winds will continue to load weak layers. Natural avalanches may break up to 5 feet deep on steep slopes facing NW-NE-S. You are most likely to trigger a large and destructive avalanche in locations where the weak layer is closer to the surface. This includes slopes that are raked by winds or peppered with rocks.  

    You are unlikely to notice obvious signs of instability, like collapsing or cracking, before triggering a slide. Snowpit tests may yield variable results, so rely on snowpack structure and recent avalanches when making decisions.

    Your simplest and safest option is to avoid this problem by selecting low-angle slopes that are not connected to steep terrain. 

    (3/8/2026)

    A large natural slab avalanche on the slopes below the Little Matterhorn in the Avalanche Lake basin. This avalanche likely occurred when a smaller avalanche stepped down to a weak layer. The blue arrows indicate the crown of the thinner slab avalanche. Wind-drifted snow will continue to overload buried weak layers. Natural and human-triggered avalanches are possible on this layer. 

    Photo: Rob Millspaugh

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Winds from the south and west are building thick and potentially sensitive drifts above the recent snow line. Look for these downwind from saddles, ridgelines, gullies, and ribs. Slabs will become thicker and more widespread as you climb in elevation.

    Blowing snow will point toward fresh wind slabs. Etched surfaces signal wind-affected snow, while collapsing indicates a firm slab over softer snow. Cracks shooting away from your feet or machine confirm you have found a sensitive slab. Growing cornices may fail, triggering a slide on the slope below. 

    Strong winds may cause slabs to form further down slope than you might expect. Slabs may range from soft to hard. Hard slabs will support the weight of a rider and may not give obvious signs of instability before breaking. 

    (4/3/2022)

    A natural wind slab avalanche. Reduce your chances of triggering an avalanche by steering around stiff surface snow, especially along ridgelines, saddles, and ribs. Strong winds may have formed slabs further down slope. 

    Photo: burket M kniveton

Avalanche Discussion

I'm placing my uncertainty squarely in the middle of the road today. I am certain there will be wind, that wind slabs will form in leeward terrain, and that this will apply a load to buried weak layers. I am less certain how these weak interfaces will hold up to another incremental load. 

Layers of facets and surface hoar formed in January and mid-February have shown some evidence of "healing" during the last week; however, we can't be sure exactly how much load it will take for them to reactivate. A fairly continuous string of large natural and remotely-triggered avalanches suggests that it doesn't require much. Below the recent freezing level (which has varied), liquid water in the snowpack might have complicated things. In locations where the snowpack is thinner, it is possible that weak layers have been further compromised by rain and meltwater infiltration. This may or may not have been a factor for a very large avalanche in Glacier National Park (see below). Today's colder temperatures should help mitigate this effect.

Yesterday (Sunday), a frequent contributor to the forecast returned to the Avalanche Lake area of Glacier National Park to follow up on a suspected avalanche that they heard while traveling in the area on 3/6. With better visibility, they confirmed that a very large and destructive (D3) avalanche had run on a northerly slope at 6200 feet.  Likewise, in the Swan Range, a party reported a large avalanche on Aeneas Ridge. These are the reports that keep us on edge during each loading event. A significant test will come later this week as a potent storm arrives. Expect increasing danger at that time. 

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