Avalanche forecast

Flathead Range & Glacier NP

Flathead Avalanche Center
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Avalanche danger

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

Skier-triggered slides on Saturday confirm that releasing a 1-2 foot thick slab avalanche on a buried weak layer remains possible. Pay attention to changing snow surface conditions throughout your tour. Treat upper-elevation shaded slopes with respect, as these slopes can catch you off guard and are suspect of sliding in surprising ways.

Avalanche problems

  • Persistent Slabs

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

    A slide on Saturday confirms it is still possible to trigger a slab that breaks 18 to 24 inches deep on thin layers of weak snow above the very hard, early February ice and crust layer. These layers are better developed on shady, upper-elevation slopes but are also found on isolated sunny and mid-elevation slopes. 

    Saturday's warming and recent winds have stiffened the snow surface, forming a slab in many locations. The slab was the missing ingredient, which may be why observations have noted few avalanches on this layer until yesterday. Choose terrain free of convexities to limit the chance of triggering a slide. Steer around thin areas, such as those scoured or peppered with rocks, in favor of a deeper, more consistent snowpack. Cracking beneath your boards or machine indicates an unstable slab directing you to lower-angle terrain. 

    (2/17/2024) Photo: Zach Miller

    A view of the crown of a persistent slab avalanche triggered by a skier on 2/17/24.

Avalanche Discussion

Following a week of well below-average temperatures, yesterday's sunshine resulted in southerly slopes feeling like spring. However, air temperatures remained cool with just one mid or upper-elevation station, Hornet (6500'), warming above freezing.  

As expected, the strong mid-February sun affected the cold, dry snow surface on steep southerly aspects. Most observations noted loose snow slides that ran on Friday or Saturday (Observation), with one party witnessing a D2 dry loose slide in action (Observation). At the same time, another group watched a small dry loose trigger a storm slab, resulting in a D2 slide (Observation). 

On Saturday, two parties in the Marion Lake area above Essex unintentionally triggered large slab avalanches. Our limited knowledge of one incident where a member was injured is found here. A skier triggered a slide that caught another member of the party below. The victim was carried through small trees and came to rest, partially buried and injured. Two Bear Air extracted the individual, who was treated for serious but non-life-threatening injuries. Another party had skied a nearby slope earlier in the day. An Extended Column Test they conducted before skiing scored ECTN; it broke but did not propagate on an interface between storm layers within 2 feet of the surface. We believe the slide was on an east aspect above the head of the lake, but we are not sure of the elevation. We will update our website with more information as it becomes available.

A thorough observation by the other party is here. This observation contains a wealth of information, and we appreciate this group for sharing this information in the name of public safety. This avalanche fractured with the third skier on the slope at the skier's skis and ran full track through a convoluted avalanche path. The slide was on a north aspect at 7100' and failed as a hard slab on a layer of facets above the early February crust. The party noted, "The avalanche caught us completely off guard, given our other observations throughout the day on similar aspects and at similar elevations." They also shared this pearl of wisdom, "Please keep heads up out there and don't get lulled into a false sense of security because you aren't finding the problem everywhere - that's the sneaky part about persistent weak layers."

The bluebird weather allowed for views of avalanche activity associated with the late-January and early February warming and atmospheric river along with the February 11 and 12 storm cycle. Check out these observations for more details (Observation 1, Observation 2, Observation 3).

Upcoming event: Flathead Avalanche Friends Fest, February 21-24. We have four days of events on tap for you: Beacons & Brews, Name That Tune/Name That Avalanche, Workshop Night with State of the Snowpack and USGS, Hot Dog Days, and the Ultimate Après with Backcountry Partner Speed Dating and the Big A$$ Raffle. More info at flatheadavalanche.org/event/friendsfest

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