Bulletin d’avalanche

Flathead Range & Glacier NP

Flathead Avalanche Center
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Danger d’avalanche

Sat
Alpin
2 · Modéré
Limite forestière
1 · Faible
Sous la limite
1 · Faible
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Recent snowfall has improved the riding but increased the avalanche danger. Wind may be drifting snow into fresh thin slabs at upper elevations. Wind-sheltered terrain may hold isolated small slabs. You could trigger slides from gentler terrain below, above, and to the sides of steep slopes. 

The avalanche hazard is more widespread in the Swan Range, where more snow fell.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2

    Since Thursday morning, the Whitefish Range, Flathead Range, and Glacier Park have picked up several inches of new snow. This fresh snow rests on weak faceted snow or surface hoar in many locations, adding to its instability. Due to the underlying weak layer, slabs may be triggered remotely or from a distance. The wind has been generally light to moderate but strong enough to transport snow in favored locations. Look for fresh slabs forming below ridgelines, saddles, or cross-loaded gullies. On slopes sheltered from the wind, thin slabs may have developed.

    You have found a slab if you suddenly notice your skis, boards, or machine not sinking as deeply into the new snow. Utilize hand pits to see how well the fresh snow is bonding to the old surface. Cracking in the snow surface indicates an unstable slab and directs you to seek out lower-angle terrain.

      

    (12/27/2023)

    Prevailing westerly winds scour windward slopes and deposit snow onto leeward aspects of Glacier View Mountain.

    Photo: Mark Dundas

Avalanche Discussion

Snowfall and precipitation totals for the system, which impacted our area Thursday into Friday, were disappointing. Noisy Basin, in the Swan Range, took home the lion's share with a respectable 1 inch of water; however, most other locations recorded just several inches of snow and around 1/3 inch of water. These totals should increase slightly before this system moves out of the area sometime mid-morning. Fortunately, unsettled weather continues through the weekend with widespread light snow and seasonably cool temperatures.

The new snow fell on weak faceted snow or surface hoar in many locations. If slabs develop on the underlying weak layer,  they might be more reactive to the weight of a rider than anticipated. There is the possibility of triggering slides from above, below, or to the sides of a steep slope. Slides may break wider and higher above you than expected. Today's triggered slabs may act more like a persistent slab than a storm or wind slab.

Today, we are listing storm slab, wind slab, and loose dry across the three zones, which are all new snow avalanche problems. As snow piles up through the weekend, the avalanche danger may increase as a thicker and stronger slab develops on top of weak snow. We expect to transition to a persistent slab problem in the next day or two. 

Régions couvertes