Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Sat
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 6 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

It remains likely that a skier or snowmobiler could trigger a large avalanche 2 to 4+ feet deep on a buried weak layer. Strong southwesterly winds have formed fresh slabs on leeward slopes. Finding a gentle slope that is sheltered from the wind will provide good riding conditions while providing for a margin of safety.

The danger may increase in the Flathead Range, Glacier National Park, and the eastern Whitefish Range this afternoon IF forecasted snow occurs earlier than expected.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    2–3

    Yesterday’s (Thursday) strong southwesterly winds stiffened the snow surface that caps a widespread weak layer of surface hoar or facets above a crust. These weak layers were responsible for a rash of human-triggered and natural avalanches over the last several weeks. Direct feedback, such as whumphing or collapsing, will wane as the snow surface stiffens from the wind. Triggering an avalanche that fails on this layer will be 2 to 4+ feet thick and difficult to escape if caught.

    Shallow parts of a slope (rocky outcrops, buried stumps, or areas of less wind effect)  will put you closer to the weak layer. Avoid these areas as they are likely trigger points for a large, destructive avalanche.

    Choose slopes that are less than 30 degrees and face the sun in order to give yourself a wide margin of safety. Avalanches can pull back further on a ridgeline or wrap around terrain features, and be triggered remotely from the bottom or side of a slope. Disconnect yourself from terrain where you see these common characteristics:

    • Shaded aspect (NW-N-SE)
    • Steep (greater than 30 degrees)
    • Open to the sky (treeless or trees that are sparse enough to easily travel through).

    Remotely triggering large avalanches is still possible. Note the terrain trap that this avalanche slid into. Being buried under a 2 to 4+ foot-thick slab in a common terrain feature like this would make survival difficult.

    (2/24/2026)

    Photo: Cam Johnson

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    Strong southwesterly winds have formed fresh slabs on leeward slopes downwind of saddles and exposed ridgelines,  and on gully sidewalls. Dunes, pillows, and drifts are visual clues that you are transitioning into an area of wind-affected snow. Cracking under your foot or machine indicates that you’ve found an unstable slab.

    Steer yourself into lower-angle, protected terrain, where you will encounter lighter, less dense snow conditions. Areas of the Flathead Range, Glacier National Park, and the eastern part of the Whitefish Range could see a chance of snow this afternoon. Expect fresh snow and wind to increase the sensitivity of freshly wind-affected areas.

    Winds have loaded the same slopes where a buried weak layer is present. Any triggered fresh wind slab could possibly step down, resulting in a much larger and more deadly avalanche described in the Persistent Slab problem above.

     

    Exposed areas, below ridgelines, will harbor fresh slabs of wind-drifted snow. Avoid travel if you see cracking under your feet or sidehilling your snowmobile becomes difficult.

    (2/26/2026)

    Photo: Guy Zoellner

Avalanche Discussion

Last weekend, it was common to hear reports of whumphing, collapsing, and remotely triggered avalanches. Currently, due to the wind stiffening and thickening the surface slab, those clues are more difficult to find. In areas where the slab is thinner, riders are likely to trigger a large to very large avalanche as their weight impacts the weak layer.

Structurally, the buried surface hoar is still present. As snow depths increase and slabs harden from the wind, reactivity will begin to slow. However, if triggered, the resulting avalanche will be 2 to 4+ feet thick, run very fast, and potentially wrap around terrain features.

Continue to tiptoe around the mountains. It will be easy to be driven onto a dangerous slope while hunting for quality, non-wind-affected snow. The well-documented Persistent Slab problem that has plagued us for weeks is still in the room, it just isn’t screaming at the table.

Regioni coperte