Lawinenlagebericht

Whitefish Range

Flathead Avalanche Center
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Lawinengefahr

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

The riding is excellent, but there remains the possibility that you could trigger a slide on a weak layer buried 1-3 feet deep.  This is more likely in areas where the wind has stiffened the surface or the snowpack is thinnest, such as convexities and slopes peppered with rocks. If you are unsure of what is beneath the surface, lower-angle slopes offer a safer experience.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    Several layers of facets, faceted crusts, or surface hoar are found in the top several feet of the snowpack. The likelihood of triggering a slab avalanche on one of these weak layers decreases but remains possible in the Whitefish Range. The recent storm snow has added stress to these layers but is also strengthening them from the overlying weight. Warm temperatures before Christmas were helpful in the strengthening process. In some locations, they are buried to a depth that a rider or snowmachine may not impact.

    The most likely spot you could trigger a slide would be where the weak layer is closer to the surface, such as wind-scoured locations, convex rollovers, slopes peppered with rocks, or a thin area on the edge of a slab. 

    (12/30/2024)

    A rider triggered avalanche that failed on facets buried in mid-December.

    Photo: Cam Johnson

Avalanche Discussion

Post-storm observations emphasize dry snow, limited wind effects, and excellent riding conditions. The lack of wind at upper elevations for this length of time is nearly unfathomable. The wind station that often reports the highest wind speeds of any station in the Flathead is on Aeneas Ridge in the Swan Range. Rob and Cam visited the station yesterday (Wednesday) to knock rime and snow off of it. They noted that the calm to light winds produced little to no drifting, and windward slopes have a remarkable amount of unconsolidated snow available for transport.

On Wednesday, a rider noted a large soft slab avalanche just east of Peter’s Ridge on the east side of the Swan (Observation). This slide was estimated to be 500 yards wide and 2 to 4 feet deep and occurred at 5800 feet. This likely failed during the recent record-breaking snowfall event where the nearby Noisy Basin Snotel recorded a whopping 5 inches of water in around 30 hours.

This morning, we dropped the storm slab hazard from likely to possible at upper elevations in the Swan, Glacier Park, and Flathead Range. We reason that storm slabs strengthen within a few days of forming, and it has been several days since our recent heavy-loading event. When the wind returns, thick slabs of wind-drifted snow are expected to develop, and we may need to add Wind Slab to the problem list.

We also dropped the likelihood of triggering a Persistent Slab avalanche to unlikely in the Flathead and Swan zones. We kept it as possible in the Whitefish due to less recent snowfall; subsequently, the weak layer is closer to the surface. Further observations will determine if we can remove this problem. 

Downloaded the app yet? 

You can now access our region's forecasts, observations, and weather data directly from the Avy App (IOS; Android). Many features are accessible offline, so you can doublecheck danger ratings and travel advice on the drive to the trailhead or in the backcountry. 

Events and Education:

Want to start your New Year on the right foot? Sign up for a Partner Rescue Clinic for motorized Riders on January 4. Check out our calendar for other upcoming events. 

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