It remains possible to trigger avalanches that break one to two feet deep. These slides are most likely on slopes steeper than about 35 degrees where snow depths are variable, thanks to drifting and scouring by recent winds. To reduce your chances of finding slopes like this, stick to slopes sheltered from the wind and sun. Whumpfing collapses are a clear sign of danger.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
To reduce your chances of triggering an avalanche that breaks on old snow, avoid riding across likely trigger points. You can recognize these spots by looking at a slope’s shape and runout. Steer away from convex rollovers, unsupported slopes, and old slabs of drifted snow near ridgelines. Avoid lines that put you above terrain traps, like rocks, trees, or gullies. These can magnify the consequences of triggering a slide.
Talk, talk, talk… It’s easy to tune out when your crazy but harmless aunt or uncle is repeating stories at a holiday meal. When it’s the snowpack, though, it’s worth paying attention. And the snowpack has been saying something meaningful since our last storm. Specifically, the whumpfing collapses people continue to report are clear signs that it’s still possible to trigger avalanches large enough to injure or bury you.
The problem is slabs formed by December’s storms. These slabs are sitting on soft, weak snow that’s buried one to two feet below the snow surface, often around crusts. In some cases, the weak snow is close to the ground. A person’s weight can still collapse these weak layers, as evidenced by the whumpfing collapses. On steep slopes, those collapses will produce avalanches. So hearing a whumpf is a clear sign of the problematic snow structure nearby. Avoid trouble by sticking to lower-angled slopes.
If you’re not hearing whumpfs, reduce your chances of triggering a slide by picking slopes that have fewer trigger points and lower consequences if a slide does happen. Likely trigger points include convex rollovers, rocky areas with thin snow cover, and open slopes where strong winds drift and scour away snow. Slopes with lower consequences are those that end in open runouts free from trees, rocks, and gullies.
The reports of collapsing have been most regular in the eastern parts of our forecast region, notably the Lake McDonald and John F. Stevens canyon areas of Glacier National Park. We’ve also had reports of collapses in the southern Whitefish Range above Canyon Creek. Observers across the region are reporting propagation in snowpack tests on weak snow about two feet below the surface. Many of these tests results occurred on southerly slopes, but that could just be a lack of data from northerly slopes.
Snow showers, diminishing through the day, with minimal accumulations. Light northwesterly winds with cool temperatures. A weak weather system will pass over the region tonight and tomorrow, bringing more snow showers and continued cool temperatures.
| Thursday | Thursday Night | Friday | |
|---|---|---|---|
| Cloud Cover: | Mostly Cloudy | Mostly Cloudy | Mostly Cloudy |
| Temperatures: | 16 to 26 deg. F. | 7 to 12 deg. F. | 15 to 20 deg. F. |
| Wind Direction: | Northwest | West | West |
| Wind Speed: | 5 to 10 mph, Gusting to 20 mph | 5 to 10 mph, gusting to 15 mph | 5 to 10 mph, gusting to 20 mph |
| Snowfall: | 0-2 in. | 0 in. | Trace to 1 in. |
| Snow Line: | 0 ft | 0 ft | 0 ft |
This forecast applies only to backcountry areas outside established ski area boundaries. The forecast describes general avalanche conditions and local variations always occur. This forecast expires at midnight on the posted day unless otherwise noted. The information in this forecast is provided by the USDA Forest Service who is solely responsible for its content.
