Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Wed
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

With the weather forecast for today, avalanche conditions remain complex and very dangerous. Large to very large natural avalanches are likely at upper elevations; the debris from these slides could entrain wet snow and run into mid- and low elevation terrain. Wet snow avalanches are likely at mid-elevations. The best and safest travel today is somewhere else.

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    The surface snow on steep slopes will become wet from rain, rising temperatures, or direct sun; as it loses cohesion, wet loose snow avalanches are likely.  Clear signs of of these processes include rollerballs fanning down a slope from trees, rocks, or your skis, board, or snowmachine. Move off and out from under steep slopes when and where these conditions exist. They will be most widespread on slopes getting wet for the first time, which are generally slopes above Monday's rain line (roughly 6500 to 7000 feet), or shaded mid elevation slopes.

    Water percolating down below the surface can weakend and destabilize weak layers and weak interfaces, causing wet slab avalanches. These are less likely, but no less dangerous. They're also more unpredictable. 

    Rollerballs and debris from wet loose avalanches can trigger slab avalanches deeper in the snowpack.

    (2/5/2025)

    Wet loose activity on a steep and rocky southerly slope. 

    Photo: Flathead Avalanche Center

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–3.5

    Recent and drifted snow is settling and consolidating into reactive slabs 1 to 3 feet thick. Slabs where the surface snow is getting wet for the the first time may release naturally; these conditions will be most likely on upper-elevation, westerly slopes with rising temperatures, lingering rain showers, and clearing skies this afternoon. These slabs will remain sensitive to the weight of a rider or snowmachine on other aspects and at mid-elevations.

    Avoid riding on or below steep start zones, particularly if the sun breaks through the clouds or rain showers are occurring. 

    (2/1/2025)

    Storm slabs remain sensitive to the weight of a rider at mid-elevations today.

    Photo: Mark Dundas

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3.5

    Monday's avalanche activity demostrated that large and very large avalanches can release on weak layers buried deep in the snowpack, or even near the ground, given large triggers. And today, large triggers are likely - wet loose slides, slabs in the surface snow, and falling cornices. Darn good reason to avoid the runouts of steep, upper-elevation start zones. Especially those that are unsupported, convex, or have snow cover that varies in depth due to wind scouring and drifting. 

    These slabs remain unlikely to release with light triggers - like your weight - but you're unlikely to get on slopes with the above characteristics today, right?

    (3/24/2025)

    Persistent slab avalanche releasing on an unsupported, rocky, upper elevation slope. Skyland region. 

    Photo: Michael Reavis

Avalanche Discussion

The limited observations from Monday (all from the Flathead Range) indicate the region saw a widespread cycle of large and very large natural avalanches. Most involved wet surface snow failing on steep slopes, triggered by rain showers, direct sun, and rising temperatures. This before and after image is a good example. Large dry slab avalanches ran on many leeward, upper-elevation slopes. And some very large natural avalanches released on weak layers buried mid-pack, or near the ground. Using the trees in this image, it appears some crowns were over six feet deep. To be clear, those reports are all from the Flathead zone; we have no reports from the other zones. The pattern I see is wet snow avalanches below the rain/ snow line and dry snow avalanches at upper elevations - roughly above 6800 feet.

With temperatures remaining above freezing overnight yet forecast to rise into the 40s even at upper elevations, what can we expect today? To be frank, I'm not sure. This is a new pattern for me, even with 30+ years in the business. My biggest uncertainty - and concern - is conditions at upper elevations. We've seen 2 to 4 feet of new snow above 6500 feet in the past week, often accompanied by powerful winds that drifted it into thicker slabs. Avalanche activity diminishes with an end to precip and diminishing winds - that's basic, right? But we've got rain showers, late-winter sun, and freezing levels rising above the summits of the highest peaks in Glacier NP today. Monday afternoon, brief sunny periods were enough to trigger large natural avalanches in the Skyland area. Check out Lydia's video in the media section to see it happen. 

Here's my best guess: we'll see more natural avalanche activity today at upper elevations. Less than Monday. However, some slides may run from start zones well above 7000 feet, where slabs of new and drifted snow are even thicker and larger than most of what we've seen as of today. So I expect fewer but bigger slides. And the instability could jump rapidly, with a rain showers or a few minutes of direct sun. Westerly slopes may be the most likely to join the party, because late in the day, temperatures will be warmer and direct sun stronger.

In the Swan and Whitefish Ranges, freezing levels have already climbed above all but the highest summits. Wet snow avalanches will be the most widespread hazard; Considerable danger. Keep in mind that the uncertainty is highest in those zones because of the lack of obs.

In the Flthead Range and Glacier National Park, there's still plenty of real estate above freezing levels this morning. Plenty of leeward start zones and upper elevation terrain with dry snow. Given the complexity and the potential for destructive avalanches that run to low elevations, I'll keep the danger at upper elevations at High/ L4 for the Flathead Range. As Mike noted in our discussion this morning, "The safest riding today will be on slopes that slid to the ground with no hangfire." The best riding might be on a bike, even if it's raining. 

All the warming, rain, and meltwater are increasing the likelihood that open glide cracks will fail. Many of these are camoflaged by recent snow. Be alert for rumpled snow surfaces on steep, southerly slopes, particularly in the Swan Range.

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