Bulletin d’avalanche

Flathead Range & Glacier NP

Flathead Avalanche Center
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Danger d’avalanche

Fri
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

Enjoy today’s storm snow by sticking to lower-angled slopes. New and wind-drifted snow will increase the likelihood of human-triggered avalanches. Avalanches will be more common in areas where wind drifts snow into thicker slabs, or in areas favored by new snow. A triggered avalanche in the new snow may step down to weak layers buried deeper in the snowpack, causing a more destructive avalanche.

Expect Moderate danger in areas that do not see forecasted snow totals.

Problèmes avalancheux

  • Wind Slabs

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

    Strong southwest winds will drift new snow into fresh slabs downwind of ridges, saddles, and crossload terrain features further downslope. Slabs of drifted snow will be larger in areas favored by new snow, or along ridge crests that receive stronger wind speed averages. If you see more than 8 inches of new snowfall, expect a storm slab avalanche problem, which will broaden the distribution of the avalanche problem to all aspects.

    Identifying and avoiding this problem today should be straightforward. Avoid areas where you see blowing snow. Shooting cracks around your boards or machine indicate that conditions are ripe for human-triggered avalanches. Keep your slope angles low or stick to terrain sheltered from the win.

    (12/21/2024)

    Today, wind-drifted snow will grow cornices, and slabs will build downwind of them. Avoid traveling beneath features like these today. 

    Photo: Kelson Geber

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3

    Weak layers buried throughout the snowpack continue to show untrustworthy signs. Whumpfing collapses have been reported in the last two consecutive days. Reported avalanches have favored north and east-facing slopes, but isolated events have occurred on south-facing slopes.

    The most straightforward way to avoid triggering a large and destructive avalanche is by sticking to lower-angled slopes. Whumpfing collapses are signs the snowpack is unstable. Avalanches failing 1 to 3 feet deep will be difficult to escape and will be large enough to bury a person. A triggered avalanche in the new snow has the potential to step down, causing a larger and more destructive avalanche.

    (12/19/2024)

    The large debris pile shown in this photograph is a result of a remotely-triggered avalanche. This avalanche was triggered from above, and grew large enough to bury a person. This avalanche failed on a northeast aspect at upper elevations. 

Avalanche Discussion

Today’s avalanche danger will depend on the amount of new snow we receive. The storm appears to favor the northern Whitefish Range with 4 to 6 inches by the end of the day. Thankfully, it looks optimistic that the rest of the forecast region should still see 2 to 5 by nightfall. Strong winds will make up for what the storm lacks in precipitation. Expect rising avalanche danger throughout the day.

Over the past few weeks, we have highlighted a buried layer of surface hoar and facets buried about 2 to 3 feet below the surface. However, recent observations suggest that a more recently buried facet/crust may be the culprit of audible collapses (observation, observation). These collapses occurred on an east aspect at 6500 feet and another on a south aspect between 5500-6500 feet. The takeaway from these is the snowpack is variable and gaining complexity. Simple terrain selection should follow this growing complexity.

 

Régions couvertes