Lawinenlagebericht

Flathead Range & Glacier NP

Flathead Avalanche Center
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Lawinengefahr

Tue
Hochgebirge
3 · Erheblich
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

It remains likely that a rider could trigger a large avalanche where wind-drifted snow rests on weak layers. Shifting winds are making this problem more widespread. Triggering a slide in sheltered terrain remains possible. Cold temperatures and uncertainty should direct you to conservative terrain and a simple plan.  

 

Lawinenprobleme

  • Wind Slabs

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

    The Friday/Saturday storm deposited 6-12 inches of snow onto widespread weak snow and crusts. In areas open to the wind, this snow has been transported by moderate to strong south-to-west winds.  The arrival of Arctic air on Sunday has shifted the winds to the north or east, drifting snow onto atypical aspects. It remains likely that riders can trigger an avalanche at or near the interface of the new and old surface on wind-drifted slopes where dense 1-2 foot thick slabs formed.  In areas sheltered from the wind, triggering a slab is possible if you find a cohesive snow surface on steep slopes.  

    Due to the underlying weak snow, this problem is not straightforward to manage. You could trigger slides remotely—from flat terrain below, above, and to the sides of steep slopes. They may break surprisingly wide and wrap around terrain features.

    The safest way to manage this problem is to stick to low-angle terrain without overhead hazards. Avoiding areas of wind drifting in favor of more sheltered locations with softer snow will offer a more enjoyable experience. Monitor the cohesiveness of the surface snow and look for signs of a sensitive slab, such as cracking or collapsing.

    (2/1/2025)

    This varying crown thickness of this soft slab avalanche exhibits the telltale signs of wind loading. The WMR ski patrol triggered this slide with explosives just leeward of a ridgeline.

    Photo: Mark Dundas

Avalanche Discussion

Reports of avalanche activity and snowpack instability associated with the 1/31-2/1 storm have been limited to the terrain in and around the WMR ski resort. On Saturday, ski patrol, the public, and I found a reactive snowpack with long shooting cracks and slab avalanches intentionally triggered by explosives or skis. Over the weekend, parties in the central Whitefish Range, the Swan Range, and the Flathead Range report minor instabilities and small avalanches. Most parties chose sheltered terrain where the snow has generally remained cohesionless and enjoyable. We have not received reports from the alpine or wind-loaded terrain where most avalanche action likely occurred during the storm and where freshly formed slabs are most likely to remain sensitive to the weight of a person or snowmachine.

The avalanche activity and instabilities observed on Saturday resembled more of a persistent slab problem than a storm slab. This is due to the widespread underlying weak layers formed during the January drought. Shooting cracks failed at the weak layer and traveled impressive distances. Avalanches released sympathetically from the weight of a rider or an explosive air blast. In the WMR side-country, there would have been more activity had the new snow been slightly more cohesive.  

We transitioned to a wind slab problem this morning due to the wind being the driving force behind most of the recent avalanche activity and current conditions. 

 

 

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