Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Thu
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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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 most likely to trigger an avalanche in wind-loaded terrain, but could also trigger a slide on sheltered slopes. Slabs will be larger and more hazardous as you gain elevation.

The danger is not as widespread in the Whitefish Range and Swan Range, where less snow fell.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2.5

    Up to 16+ inches of snowfall and blustery southwest winds have formed slabs on wind-exposed slopes and in sheltered locations. Continued wind will increase the size and distribution of these features throughout the day. 

    The probability of triggering a slide increases with elevation and is greatest on wind-loaded slopes. Fresh cornice growth may fail naturally, triggering a slide on the slopes below.

    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.

     

    (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. 

  • Loose Dry

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

    The snowfall that is winding down left up to 8-10" on the valley floor and over a foot in favored locations at mid elevations. On wind-sheltered, steep slopes, this snow may sluff naturally or be easily triggered by a rider. In locations favored by snowfall, slides could entrain substantial fresh snow and grow surprisingly large.

    These slides will generally not be large, but they can knock you off your feet and carry you into areas you don't want to end up, such as a stand of trees or an area where snow can pile up deep. Getting tangled up with one of these in a long-running gully may make escape difficult. Mitigate this hazard by managing your sluff.

    (1/27/2025).

    Fresh snow will sluff in steep terrain today. While mostly small and relatively harmless, slides like this can push you into terrain traps such as rocks, cliffs, or trees.

    Photo: Cam Johnson

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. Check out this video Guy made from the Swan Range yesterday.

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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