Lawinenlagebericht

Whitefish Range

Flathead Avalanche Center
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Lawinengefahr

Tue
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

It is possible to trigger avalanches that break on weak layers buried 1 to 3 feet deep. This hazard may be most widespread where these layers are under stiff slabs of wind-drifted snow. You could trigger loose snow slides in the recent low-density snow on very steep slopes. Smaller slides in the new snow can initiate a larger slide. 

 

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    1–2

    Fresh snow has added weight to weak layers buried 1-3 feet below the surface. We don't believe this low-density snow is enough to tip the balance; however, the chance of triggering a large avalanche on these layers is concerning. Slides will be more likely where the wind stiffened the surface snow into a cohesive slab. Suspect slopes include those with signs of wind effect, such as pillows, dunes, and etched surfaces. Buried weak layers (facets, faceted crusts, and surface hoar) are found on many slopes at all elevations and rest beneath February's snowfall. 

    Slopes that will be easier to trigger will be steep (35+ degrees) or associated with a convexity or rollover. In many places, these layers are close enough to the surface to remain sensitive to the weight of a rider. In deeper drifted areas, avalanches will be easier to trigger in thin spots at the edges or where rocks stick out of the snow.

    Signs of instability have been concentrated in the Whitefish Range, where multiple groups continue to report collapsing (whumpfing), shooting cracks, and a triggered avalanche. Observers in other ranges report fewer incidents with the buried weak layers. Thursday's avalanche (Attached image) confirms you can trigger avalanches remotely—from flat terrain below, above, and to the sides of steep slopes.  This is a good reminder to be mindful of the overhead hazard above you.

    (2/15/2025)

    This image shows the skin track and approximate location where a remotely triggered hard slab avalanche occurred on 2/13/25. The slope angle varied between 30 degrees at the trigger point to 40 degrees at the crown. 

    Photo: Mark Dundas

Avalanche Discussion

The precipitation recorded this morning was slightly less than forecast, as the brunt of the system affecting Western Montana is just south of our area. Noisy Basin in the Swan Range picked up 0.5" of water, with roughly half that amount elsewhere. The further south you travel in the Swan, the more new snow you should encounter. Snowfall will continue in the Swan Range throughout the day, while precipitation in the Flathead Range and Whitefish Range tapers off. 

Fortunately, winds are forecast to remain light through the day. Still, if they pick up more than anticipated, a copious amount of low-density surface snow is available for transport into fresh slabs. If this occurs, the danger will increase later today. Winds will primarily remain out of the north and east, which can form slabs in unusual locations, such as the canyon floor in the Highway 2 corridor and the Swan Front. 

Slides in the new snow will have the potential to step down to buried weak layers and trigger a much larger avalanche. The likelihood of a Persistent Slab avalanche failing may increase as the additional weight from snowfall and wind-blown snow will stress the weak layers formed during the January drought.

Upcoming Events: Check out our calendar and sign up now!

  • February 20-22nd: Avalanche Safety: Introduction to Avalanches Human Powered for Skiers and Snowboarders - register here
  • Feb 26th - Pint Night at Blackstar with donations going to Flathead Avalanche. State of our Snowpack presentation at 7 pm! 

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