Avalanche forecast

Swan Range

Flathead Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Weak layers buried beneath slabs of drifted snow remain our primary concern. Natural and remotely triggered slabs occurred in the last week. Significantly reduce your chances of running into this problem by selecting south through west aspects where this weak layer has yet to be found.

Avalanche problems

  • Wind Slabs

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

    Old and new wind slabs rest over a fragile layer of buried surface hoar. 3 of 4 observations above 6000 feet in the Swan Range report unstable pit results, or remotely triggered avalanches. Currently, this persistent weak layer appears to be a problem where winds drifted snow into thicker slabs. You can reduce your chances of triggering a slab avalanche on slopes that typically get hit by the sun and westerly winds. If your travels take you to upper elevation slopes where you suspect wind-drifted snow, keep slope angles less than 35 degrees. 

    (1/15/2023)

    Natural avalanche that failed in the last week. 

    Photo: Cam

Avalanche Discussion

Observations from yesterday (Monday) generally point to relatively safe avalanche conditions. New snow accumulations appear to average roughly 5 to 8 inches. One rider found this new snow to sluff easily in steep terrain in the Flathead Range, and another person found this new snow slabby and breaking above the crust in the Whitefish Range. Mark and Sarah found the recent melt-freeze crust up to 6700 feet in the Swan Range. Temperatures dropped below freezing at all elevations, reducing the chance of wet snow avalanches.

Today winds are forecast to increase and average between 10 to 15 mph at upper ridgelines. I suspect southwesterly winds will drift snow into small, thin slabs below ridgelines and gullies. These slabs should be relatively harmless in size and easy to manage by tucking in below areas of active drifting. Select terrain sheltered from the wind or choose windward aspects. 

Slabs of drifted snow are more of a concern in the Swan Range. A weak layer of surface hoar was buried on January 9th. On January 11th, a rider remotely triggered a large slab avalanche at 6200 feet. On January 15th, my partner and I remotely triggered two slab avalanches above 6500 feet. These failed roughly a foot thick. Yesterday, Mark and Sarah searched up and down on the west side of the Swan Range and could not find this layer reactive in snowpit tests. So far, this proves the distribution may be “spotty,” or harder to find. Right now, our primary travel advice for the Swan Range is to steer towards aspects that face south and west to reduce your chances of triggering a slab avalanche. Choose lower angled slopes if you decide to ride where winds drifted snow into thicker slabs. 

With recent rain and warm temperatures, we suspect this layer of surface hoar more of a problem at upper elevations, but added middle elevations for a wider margin. So far this problem is only found in the Swan Range. 

Regions covered