Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Tue
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Very dangerous avalanche conditions are developing thanks to unseasonably warm air and the potential for partially sunny skies today. Avoid traveling on or below all steep slopes; large natural wet snow avalanches are likely. Also rising is the danger posed by large to very large avalanches that release on deeply buried weak layers and run long distances. The debris from both hazards will be dense, heavy, and almost impossible to escape. 

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–3

    Large natural wet snow avalanches ran yesterday (Sunday) and we can expect more with higher freezing levels and partially clearing skies today. The snow surface on upper elevation slopes will become saturated, particularly on sunny aspects.  Debris from natural slides will entrain large amounts of wet snow and run long distances. Very large natural wet snow avalanches are possible in slide paths with continuously steep or confined pitches, making mid and low elevation runouts dangerous places to travel. That includes snow-covered roads and groomed snowmobile trails that normally feel safe. 

    Keep your distance from steep slopes. 

     

    (1/28/2024)

    Wet avalanche debris. This photo is taken from FR 115 near Red Meadow in the Whitefish Range. The avalanche ran onto FR 115 but didn’t cover entire trail. Expect similar avalanches today. 

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–3

    Look above you while traveling today, even on uptracks, snowmobile trails, and snow-covered roads that normally feel safe.  Warm temperatures and rain are increasing the potential for destructive, dangerous avalanches that break 1 to 4 feet deep in the snowpack, on weak snow around old crusts. These can fail naturally when water percolates into weak layers, or when clobbered by falling cornices and wet loose slide debris. The likelihood and distribution of these triggers is increasing. 

    Keep the word "unpredictable" in mind; fractures can propagate long distances, and the timing of instability is hard to see coming since the flow of meltwater into deeply buried weak layers is highly variable. The most reliable way to reduce your exposure to this hazard is simply to keep well away from steep slopes. That includes the runouts of large start zones well above you and short, steep cutbanks adjacent to snowmobile trails and in gullies and streambeds. 

    (1/28/2024) Large, natural hard slabs like this one are likely today.

Avalanche Discussion

While people often talk about a "January thaw" in the Flathead, this is something. Nearly all stations at mid elevations have recorded air temperatures above freezing for the past 48 hours, with 0.2 to 0.5 inches of rain. Freezing levels are forecast to climb higher today, possibly to near 10,000 feet. Although the rain looks over, it'll be replaced by partially clearing skies. So solar radiation will add to the energy that's producing meltwater on upper elevation, sunny slopes. 

The wet snow and meltwater are creating very dangerous avalanche conditions. Large to very large natural wet snow avalanches are likely on steep slopes at mid and upper elevations. Debris from these slides may reach low elevation runouts. Even slides that stop after short distances can involve large amounts of debris, as seen in the one observation we received Sunday. A rider reported multiple slides that hit or almost hit the snowmobile route across Red Meadow Pass in the central Whitefish Range. These released at mid elevations and only ran several hundred feet, but piled up more than enough debris to bury a person. I expect more of the same today, with most activity on upper elevation sunny aspects. The hazard is isolated at low elevations, because slides won't involve dangerous amounts of debris. There just as likely; I ran across two small debris piles on the Whitefish Trail near Lion Mountain Sunday. 

The danger posed by the lingering Persistent Slab avalanche problem is also increasing, as water percolates into the snowpack. The snowpack structure is weakest on sunny aspects at mid and upper elevations; that coincides with slopes where solar radiation will produce more meltwater today. This water will reach old, faceted snow above crusts soonest in terrain where these layers are closer to the surface. That describes the southeast corner of the forecast region - JF Stevens Canyon, Marias Pass, and the Skyland area, where observers have reported audible collapses and propagation in stabilty tests the past few days (Elk Mountain, 6996 Friday and Saturday, Challenge Friday). While cornices have been smaller than usual this season, there's still plenty of snow that can fail in these warm temperatures, producing debris that can tirgger deeply bured weak layers on slopes where a person might not. Leeward start zones near the crest of the Flathead, Swan, and Whitefish Ranges are prime candidates for these conditions. 

It's important to note that our confidence in today's forecast is moderate. We have no direct measures of the amount of meltwater at the snow surface or how deep it's percolating in the snowpack. The natural avalanche cycle may have peaked late last night. I wouldn't use that uncertainty to justify riding steep slopes.

Regions covered