Avalanche forecast

Swan Range

Flathead Avalanche Center
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Avalanche danger

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

On Sunday, riders triggered avalanches 6-12 inches thick on wind-drifted features in the Swan Range. Slabs of drifted snow may remain sensitive to the weight of a rider due to the weak snow they rest on. Give dune-shaped drifts a wide buffer while seeking out terrain sheltered from the wind. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–1.5

    Look for and steer around signs of obvious drifting near ridgelines and on cross-loaded gullies further downslope. Pillowy-looking surfaces or surfaces with a textured appearance are visual clues of a Wind Slab. Slabs of drifted snow should be harmless in size by themselves, though they could be consequential if caught above a cliff or stand of trees. Slopes sheltered from the wind will hold safer and better riding conditions. 

    Winds shifted to the east in the last 24 hours. Mount Aeneas reached speeds capable of transporting snow. Although the amount of snow available to transport into slabs is minimal, it is worth keeping an eye out for drifting on atypical slopes.

    (4/2/2023)

    A snowmobiler remotely triggered this slab of drifted snow. 

    Photo: Woody

Avalanche Discussion

On Friday and Saturday, a winter storm brought 8 to 12 inches of snow to the Flathead Range/Glacier National Park forecast zone. The Swan Range and Whitefish Range received only 2 to 4 inches of snow. With this snowfall came moderate wind speeds, which are ripe speeds for drifting snow into thicker slabs. Since then, we have received numerous reports of natural avalanches, human-triggered avalanches, and signs of unstable snow. Here are a few noteworthy observations from each forecast zone (Flathead, Glacier National Park, Whitefish, Swan). 

On shaded aspects, storm snow fell on a weak layer of facets. This sugary snow is the culprit for recent avalanche activity. Unfortunately, this weak layer may be slow to heal, which is one of the reasons we transitioned to a Persistent Slab avalanche problem in the Flathead Range. Another reason is that avalanches are breaking in surprising ways by wrapping around terrain features and being remotely triggered. This requires a wider margin for error by putting more space between you and the steep slopes that harbor this structure. This structure is primarily found on northerly aspects above roughly 6000 feet.

On south and west-facing slopes, recent snow fell on a melt-freeze crust. Observations suggest that it is less likely to trigger a slab avalanche on those aspects. However, if you plan to travel on solar aspects today, keep an eye on cloud cover and surface warming. If the sun sticks its face out longer than expected, plan to see some rollerballs and small wet loose activity out of steep rocky areas. This will be more common in the Flathead Range where more snow fell. A sun crust may already exist on some solar aspects.

Continue to steer around signs of wind-drifted snow in the Swan and Whitefish Ranges. Slabs of drifted snow sit on weak snow that will be slow to heal. Pockets of drifted snow should be easy to identify by their textured appearance. 

FAC will issue daily forecasts through Easter Sunday, April 9. Following this, we will give snowpack updates several times a week through April if conditions dictate. 

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