Avalanche forecast

Whitefish Range

Flathead Avalanche Center
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Avalanche danger

Sat
Alpine
1 · Low
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Out of date — this forecast expired 3 years ago.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

There remains a chance you could trigger a slide on a buried weak layer in rocky terrain or where the snowpack is thin and wind-swept. Keep an eye on today's developing snowfall. If we receive more snow than forecast, slides in wind-drifted and loose snow may surprise you.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    2–3

    Several weak layers capable of producing a large destructive avalanche can be found throughout our snowpack.

    • Faceted snow formed in November near the bottom of the pack is responsible for this month's snowmobile-triggered slide in the northern Whitefish Range and the natural slide on Elk Mountain last week (Photo above/to the right).
    • Faceted snow resting on the Christmas crust.
    • Over the past two months, a weak layer and crust combination from mid-January has been responsible for most of the Persistent Slab avalanches. This layer is generally found 2-4 feet below the surface.

    The Persistent Slab has become a low-likelihood high-consequence problem. With relatively deep snow depths across the area, these layers are generally buried at a depth that a rider is unlikely to affect. However, as recent avalanches signify, thin areas in the snowpack are likely trigger points. These include rocky outcroppings and wind-swept or scoured locations where the weak layer is closer to the surface. Last weekend riders on the east side of Glacier noted a hard slab avalanche that failed during their ascent. Mountain goats may have found one of these elusive trigger points.

    Cam and Guy deliberately broke off a piece of cornice, triggering a slide on a buried weak layer Wednesday in the northern Whitefish Range (Photo above/to the right).

    Terrain selection is the most straightforward way to deal with this issue. Choose slopes with a deep, uniform snowpack without a peppered rocky appearance. When in doubt, defaulting to lower-angle slopes is the best choice.

    (3/22/2023)

    Cornice fall triggered a Hard Slab that failed on a persistent weak layer. This avalanche occurred on a north aspect at 7100 feet. 

    Photo: Cam

Avalanche Discussion

Pacific moisture moves into the Northern Rockies today, but unfortunately, most of the snowfall will remain south of our area. The mountains around Bozeman are under a Winter Storm Warning with 1-3 feet of snow expected, while the mountains around Missoula are under a Winter Weather Advisory. Storms tracking to our south generally favor the Swan Range; this one is no exception, with 4-6 inches possible by day's end. Totals in the Whitefish Range, the Flathead Range, and southern Glacier Park are forecast to be a mere 1-3 inches.

We have added Wind Slab to the problem list for the Swan, where this problem may develop this afternoon if snowfall arrives as forecast. The avalanche danger has bumped up to MODERATE in this range. If snowfall exceeds forecasted totals in other ranges, a wind slab and loose snow problems may develop but should remain small and harmless.

Today's overcast skies and light snowfall are a change from the generally dry, sunny conditions we've experienced over the past 12 or so days. Cooler weather and cloudy skies will limit warming at the surface and end the string of days where wet loose instabilities were on our radar. This weather resulted in a crust on most sunny aspects reaching 7000 feet or higher, extending onto northwest and northeast aspects in places.

Prolonged periods of cold overnight temperatures limited the size and distribution of wet loose activity since March 12. Slides were mostly size D1 -D2, and few gouged into the underlying weak snow. All in all, an uneventful wet-loose cycle. This has been documented through the numerous public observations and yesterday in photos from an overflight of the Flathead Range (Observation) and Sarah's field day in Rescue Creek (Observation). 

Snow totals for the 2022-23 season are underwhelming. We would be in a rough spot if not for the much cooler-than-average temperatures. The summit of the WMR ski area is reporting 203" so far. Compare that to the Mammoth Mountain ski area in California's Sierra Nevada, where well over 800 inches have fallen at their summit and around 650 inches at their base lodge. This triple dip La Nina favored most of the western US except for the northern portions of Washington, Idaho, and Montana.

FOFAC Event: March 30th, 2023– Whether chasing tan lines, big lines, or both, you'll learn something valuable from FAC Lead Forecaster Mark Dundas about spring avalanche problems, how they differ from winter problems, and how to manage them. We will also discuss current conditions and concerns (or lack thereof!) with our spring snowpack. Enjoy a cold brew from Bias Brewing and a scoop from Sweet Peaks Ice Cream. The event is free and open to everyone. Begins at 6 pm.

 

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