Lawinenlagebericht

Flathead Range & Glacier NP

Flathead Avalanche Center
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Lawinengefahr

Sun
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 2 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

A little fresh snow and a lot of wind formed thin slabs that a rider could trigger. Look for signs of wind-stiffened snow and choose softer, safer snow in sheltered locations. Although unlikely, triggering a slide on a buried weak layer remains a threat, especially in areas with a thin snowpack.

Lawinenprobleme

  • Wind Slabs

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

    Wind speeds increased Friday morning and remained elevated throughout the day, transporting older surface snow and freshly fallen snow. Expect to find thin slabs of wind-drifted snow and fresh cornice growth that may be reactive to the weight of a rider, especially in favored windy locations. These features will increase in size and distribution as you gain elevation. 

    They may be found downwind of ridgelines, saddles, and terrain features such as tree stands or rock outcroppings. Cross-loaded slopes like gullies are particularly susceptible to collecting wind-blown snow.

    Look for signs that the wind has been at work: rippled surface snow, dunes, and pillow-like features. Stiff snow beneath you indicates you have found wind-transported snow. Cracking in the surface snow indicates you have found a sensitive slab. Terrain sheltered from the wind will hold higher-quality snow with generally safer conditions. 

    (1/10/2025)

    Friday's elevated wind speeds formed thin surface slabs and cornices. Weighting a pair of skis produced shooting cracks, a sign of a sensitive slab. This red flag directs you to seek out lower-angle or sheltered terrain. 

    Photo: Mark Dundas

  • Persistent Slabs

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

    Although unlikely, there remains a chance that a rider could trigger a large destructive avalanche on a buried weak layer. Facets resting on a crust and a layer of surface hoar are found 1-4 feet below the surface and were responsible for natural avalanches during the post-Christmas snowstorms. These weak layers are strengthening and showing fewer signs of instability in snowpack tests. However, we can not write them off just yet.

    Slopes where these layers are closer to the surface are most susceptible to triggering. These include windy locations and rocky terrain where the snow depth is variable. Convex rollovers are another prime location where a rider could get in trouble.

    Choose slopes with a deep, uniform snowpack free of convexities and runouts without surface obstacles or terrain traps. If unsure of what is beneath the snow surface, choose lower-angle terrain for a safer experience.

    (1/4/2025)

    The crown of a slab avalanche that failed during the post-Christmas storm cycle. This avalanche failed on a faceted crust 2+ feet below the surface.

    Photo: Mark Dundas

Avalanche Discussion

Wind speeds increased Friday morning and remained elevated throughout the day. Our windiest station, Aeneas Ridge, clocked 14 consecutive hours of average speeds exceeding 20 mph with a maximum gust of 84. Interestingly, winds tapered overnight in the Flathead Range, southern Glacier Park, and the Swan Range but remained elevated in the Whitefish Range.

Recently formed freezing rain or rime crusts limit snow available for transport in some locations.  The nastiest and most widespread crust developed in the Swan Range Wednesday, but since then, it has been capped with snow from 1.3 inches of SWE. However, an observation from the Swan Friday confirms a new rime crust to 6400 feet. We assume there appears to be enough surface snow in all zones for wind slabs to develop at mid and upper elevations. 

Yesterday (Friday), I chose a typically windy location in southern Glacier Park to determine if snow was available for transport and if the winds were at work. Yes, to both. Fresh slabs and cornice growth were small but reactive to my weight. These grew through the day and evening but should be easy to identify and avoid. A party in the Flathead Range also noted wind transport but surfy fun powder on sheltered slopes, while a party in the Whitefish Range noted no crusts and great powder.

Education opportunities: Check out our calendar for the following classes scheduled for January 25 here.

 

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