Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

Wed
Alpine
2 · Moderate
Treeline
1 · Low
Below
1 · Low
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Out of date — this forecast expired 3 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Slabs failing 2 to 3 feet thick at upper elevations remain our primary concern. Warning signs of audible collapses are becoming more sparse, however the snowpacks structure is still untrustworthy. There is a higher than usual degree of uncertainty above 7400 feet where we lack observations. If you climb above that elevation and do not feel a hard and supportable crust beneath the new snow, or see warning signs of cracking or collapsing, dial back your slope angles to 35 degrees or less. 

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Persistent weak layers buried in the middle of the snowpack and near the ground continue to gain strength, but we are not out of the woods yet.  If you venture above 6500 feet, probe around to feel for a thick crust beneath roughly 1 to 2 feet of snow. A person's weight is less likely to collapse a buried weak layer where this crust is supportable and thick. IF you are able to easily break through this crust with your foot, or you climb high enough and don't find it, reduce your slope angles to less than 35 degrees. If you decide to step out into avalanche prone terrain, expose only one rider at a time while keeping a spotter in a safe location. 

    (12/11/2023)

    A thick crust (located in the middle of this photo) is reducing the chances of triggering a large avalanche. The terrain where you do not find this crust is limited to the highest peaks in the forecast area. 

    Photo: Cam Johnson

Avalanche Discussion

A welcomed storm departed our region Monday after depositing anywhere from 10 to 20 inches of new snow throughout the forecast area. Thankfully, wind speeds for the last 48 hours have remained below optimal thresholds for drifting snow. The trend of calm and light winds will continue today. I suspect older slabs of drifted snow to have gained enough strength by now that human triggering is unlikely.

The main uncertainties rest with weak layers buried in the middle of the snowpack and near the ground. In the past 4 days, we have had no reports of signs of instability, meaning observers are not seeing shooting cracks, hearing whumpfing collapses, or observing recent avalanches on this weak layer. Those signs suggest that it is becoming more difficult to trigger an avalanche involving old snow. However, it is not impossible, and here are some uncertainties we have addressed over the last few days:

  1. The snowpack is still trying to cool down after rain and warm temperatures. Moist and wet snow is found throughout the lower half of the snowpack where these weak layers exist. The snowpack will become stronger as this snow continues to refreeze.
  2. The 12/7 crust lacks supportability in some areas of the forecast zone. Yesterday in the southern Whitefish Range, we were able to break through this crust while walking, leading us to believe that it is not impossible to trigger a weak layer below that crust. Guy and Sarah found this crust to be more robust and stronger in the Swan Range. 
  3. There is uncertainty about how high in elevation the 12/7 crust goes to. So far, we know it reaches 7400 feet in the Whitefish Range. 
  4. Cloud cover has obscured views of alpine terrain in the Flathead and Whitefish Ranges, limiting upper-elevation observations. 

Overall the snowpack is trending towards becoming more stable. Currently there is enough uncertainty at the highest elevations to keep the avalanche danger at Moderate. 

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