Bollettino valanghe

Swan Range

Flathead Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 8 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Powerful winds and fresh snow are developing dangerous avalanche conditions.  You are likely to trigger an avalanche in wind-loaded terrain where slabs increase in size and become more hazardous as you gain elevation. Choose low-angle sheltered slopes to enjoy the new snow. 

The avalanche danger is more widespread in the Flathead Range/GNP zone where more snow fell.

Problemi valanghivi

  • Wind Slabs

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

    Sustained moderate-to-strong southwest winds with extreme gusts have built fresh slabs. These will increase in size and distribution and become more dangerous as you gain elevation. Fresh cornice growth may fail naturally, triggering a slide on the slopes below.

    You will find these features near and below ridgelines, in mid-slope gullies, and behind terrain features such as rock outcroppings and ribs.

    Cornices and active wind-drifting point toward the most dangerous slopes. Due to unusually strong winds, slabs may be found in areas that are usually sheltered.

    Fresh slabs may be forming on a shallowly buried layer of surface hoar, potentially increasing instability. In these locations, slides may propagate wider than expected and possibly be triggered remotely. 

    Cracking underfoot or a sled indicates you have found a slab. Collapsing and cracks that shoot away from you (image) confirm the slab is sensitive. If you encounter a dense surface over softer snow, choose a lower-angle slope to increase your safety margin.

    Dry Loose: In sheltered locations where the snow surface remains cohesionless, you could trigger loose slides on steep slopes. Limit your time in long-running gullies, where escaping a sluff can be challenging, and above terrain traps where debris can pile up deep.

     

    (1/6/2026) Photo: Guy Zoellner

    Cracks shooting away from you or your machine indicate you have found a sensitive slab. Today, these may be common in areas where wind-loading is actively occurring. 

Avalanche Discussion

Snowfall on Tuesday and overnight favored the Flathead Range with up to 16 inches at Tunnel Ridge and 8-10" in the valley floor of John F. Stevens Canyon in southern Glacier Park. Stations in the Whitefish Range and Swan Range recorded around 5 inches. The relentless wind did not play favorites and affected the mid and upper elevations in all zones with continuous moderate to strong winds, including extreme or gale-force gusts. Check out this image of the 24-hour wind rose from Hornet in the Whitefish Range. Take a look at this video Guy made yesterday in the Swan Range.

The most dangerous conditions are in the Flathead/GNP zone, where a storm slab problem may be found on all aspects above roughly 5500 feet, and a Dry Loose problem may develop at all elevations. Less snow fell in the Whitefish Range and the Swan Range, where wind is the primary driver, creating dangerous avalanche conditions at upper elevations. 

Today is the first decent powder day in what seems like a long time coming. Enjoy it responsibly by avoiding dense, wind-affected snow and opting for soft snow on sheltered, low-angle slopes. We are still collecting data on the surface hoar layer formed during the high-pressure period at the end of December.  We do not know how it will perform under today's load.

 

 

 

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