Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

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

Continued stable weather is allowing our snowpack to strengthen and the danger to decrease. However, it remains possible to trigger an avalanche in slabs of recently drifted snow, especially at upper elevations. Continue to evaluate the snow surface for signs of thick, dense snow. Choosing sheltered terrain remains the safest option with the most enjoyable snow.

Avalanche problems

  • Wind Slabs

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

    Friday's powerful storm left dangerous slabs on the north and east sides of the compass. Relatively benign weather since then is allowing these slabs to strengthen while limiting fresh slab development. The locations where you could trigger a slide are decreasing and becoming generally confined to upper elevation slopes on typical leeward aspects. The exception is in some of the favored mid-elevation cross-loaded terrain such as John F. Stevens Canyon and the Skook Chutes.  Today's excellent visibility will allow you to spot signs of recent slab development such as a textured or a pillowy-looking appearance. Stiff, dense snow is a tell-tale sign that you found wind-affected snow while cracks shooting away from you is a clear warning directing you to safer soft snow found in sheltered terrain. 

    (1/9/2022)

    A crown of a recent slab avalanche is visible in the Skook Chutes. This slope faces south and is cross-loaded by westerly winds.

    Photo: Zach Dugan

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    1–3

    We have enjoyed a strong right-side-up snowpack for most of the season. The exception is thin, weak layers found 2 - 4 feet below the surface and near the ground. We have not received feedback that any slides associated with the recent storm involved these layers, but observations remain limited. Today will be another day of excellent visibility to look for evidence of this problem. Cam experienced collapsing or whumphing, Friday, which was most likely a sign of this problem. Besides audible failures, digging into the pack and performing snowpit tests is the only way to recognize if the slope you are on harbors these layers. When in doubt, choose planar anchored slopes over convex unsupported terrain.  

    (1/5/2022)

    A snow profile from the Swan shows softer surface snow resting on firmer mid-pack layers. Unfortunately, there is much weaker snow at the base of the pack. This is evidence of a potential Persistent Slab problem.

    Photo: Gotschalk

Avalanche Discussion

Sunday's beautiful weather allowed for great views of mountainous terrain. Reports of avalanche activity associated with our recent strong storm are beginning to trickle in, with most activity reported at low and mid-elevations. Cam was with Jenny and Kira teaching a FOFAC Level 1 motorized course in Canyon Creek, where they noted a widespread storm slab cycle below roughly 5500 feet. They spotted crowns from about 20 avalanches but nothing in the larger avalanche paths above 6000'. A rider in the northern Swan Range observed about 10 storm slabs below 5500 feet with mostly unreactive wind slabs 8-10 inches thick above that. I took a short walk up Rescue Creek and observed a handful of thin storm slabs on steep slopes around 3600,' but little in the way of activity of what I could view in the Rescue basin. The pleasant surprise was a 42-48 inch snowpack at 3600 feet which is a depth not seen in years. Another party submitted an excellent photo of a slab that pulled out in the mid-elevation Skook Chutes.

Most observations from the Flathead Range, GNP,  the southern Whitefish Range, and the Swan Range report a thick rain crust up to around 4000 - 4800 feet but great snow in sheltered terrain above that. Many snowpit tests report non-propagating results like these from The Patrol Fund Level 1 course in Canyon Creek. A party in the Flathead Range had non-propagating results but still chose to ski planar terrain less than 35 degrees in steepness. It sounds as though they had a blast, and FAC certainly appreciates and applauds their wise decision-making choices. 

This morning (Monday), we dropped the avalanche danger at upper elevations to MODERATE. Stable weather allows wind slabs to heal, but we are not out of the woods yet following the recent storm. The Patrol Fund class experienced propagating results with hard force on a wind-loaded slope on an upper elevation slope. This report confirms that it is becoming more difficult to trigger a slide in the wind drifted snow, but the threat remains possible.

The Persistent Slab problem remains on our list of problems for another day. We hope to remove this from the list, providing we do not see evidence today of slides that occurred deeper in the pack.

Regions covered