Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Know where you are today, because the avalanche type, size, and danger will vary with elevation. Nearing a ridgeline or summit, with sparse trees and winds buffeting you? Stay off steep slopes with fresh deposits of wind-drifted snow. Sheltered terrain with soft, fresh snow that's sticking to your skis, board, or machine? Avoid being on or under steep slopes where you see rollerballs and point releases of wet snow. Low elevations? Bring your rain gear and sidehilling-on-old-crusts mojo.

Avalanche problems

  • Wind Slabs

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

    Dangerous wind slabs exist at upper elevations on the lee sides of ridges, downwind of saddles and passes, on the sheltered sides of gullies and couloirs, and in other terrain features that collect blowing snow. Many of these will be hard and prone to break unpredictably, making slope cuts a risky means of gathering feedback. With winds continuing into this afternoon, I expect the freshly formed wind slabs to continue growing and be slow to stabilize. Look for softer snow and better riding on upper elevation slopes sheltered from the wind. 

  • Loose Wet

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

    Rain falling on new snow from the past 24 hours will trigger point releases of wet snow. While most will be harmless, a few sluffs may entrain enough snow to be dangerous. Look for this isolated hazard in or below start zones steeper than about 40 degrees in areas where rain is falling on 6 inches or more of new snow. Large wet loose slides will be more widespread in the Flathead Range and Lake McDonald area, where many travel routes cross the runouts or tracks of mid-elevation avalanche paths. Avoid being on or under steep slopes if you see natural or triggered rollerballs, particularly if you are above terrain traps like gullies. 

    Rain on dry snow and warming can cause wet loose avalanches. These can be an overhead hazard as you cross under steep terrian.

    Photo: Nelson

Avalanche Discussion

Focus on the altimeter today, because avalanche hazards and danger will vary distinctly with elevation. Expect dangerous wind slabs at upper elevations (above 6500 feet), thanks to the combination of new snow and moderate to strong winds in the past 24 hours. While you may also find reactive wind slabs at mid elevations, most will be small, like this one triggered in the Flathead Range Tuesday.

A second hazard at mid-elevations will be wet loose avalanches. In this band (5000 to 6500 feet) rising snowlines may produce rain on new snow. With accumulations of 5 to 8 inches in the past 24 hours at 6000 feet, point releases at in this elevation band could entrain enough snow to run long distances. They may run into lower elevations in the Flathead Range and Lake McDonald areas, where mid-elevation start zones threaten low elevation travel routes. Pay attention to rising snow levels today; your morning approach may be hazardous by mid to late afternoon. 

Both of these hazards should be short-lived. The Wet Loose hazard should diminish overnight, as temperatures drop below freezing and wet snow at the surface refreezes. Winds are forecast to diminish late today, which will allow the most recent crop of wind slabs to stabilize Thursday and Friday. The laggards will be the isolated slopes where winds deposited slabs above recently-formed surface hoar. My sense is that this combination is isolated. Shooting cracks and whumpfing collaspses are clear signs you've encountered one of these exceptions. 

 

 

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