Bollettino valanghe

Swan Range

Flathead Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
1 · Debole
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In sintesi

Saturday, riders reported natural and human-triggered avalanches failing one to two feet deep. Conditions remain similar today; riders are likely to trigger dangerous slab avalanches on a buried weak layer.  Minimize your risk by choosing sunny aspects with a supportable crust, or, where a supportable crust isn't present, stick to low-angle slopes. Slides can be triggered remotely from flat terrain above, to the side, and below steep slopes. 

 

Problemi valanghivi

  • Loose Dry

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–1.5

    The recent snowfall has left up to a foot or so of low-density snow resting on a thick, slippery crust on sun-baked slopes in the Swan Range. The new snow will likely not bond well with the underlying ice layer. Sluffing may occur on northerly slopes, but should remain small and manageable. Due to mostly cloudy conditions today, natural sluffs may be limited, but human-triggered slides are likely. 

    Slides can travel fast and surprisingly far along the underlying crust. This is an easy problem to manage and mitigate. Limit your time spent in long-running gullies where escape is difficult and above terrain traps where debris can pile up deep.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1.5–2

    Riders reported natural and human-triggered slides along with shooting cracks from the Six Mile area of the Swan Range yesterday. A widespread, well-preserved layer of surface hoar, found 1-2 feet below the surface, was most likely responsible for the activity. Additional snow and wind overnight have stiffened the surface and will keep the chance of a human-triggered slide likely today.

    The danger is greatest in terrain facing NW-N-NE-SE, where there is no supportable crust to limit your impact on the weak layer. As you gain elevation, and especially on wind-loaded slopes, the resulting slides will increase in size and be capable of injuring or burying a rider.

    In areas favored by recent snowfall or wind-loading, storm or wind slab avalanches may trigger a larger slide on the buried weak layer. 

    Look and listen for signs of instability, such as cracking and collapsing (whumpfing), which indicate you have found a sensitive slab.  Recent avalanche activity is bullseye data that the snowpack is unstable. 

    Avoidance is the best mitigation for this pesky problem. Sunny slopes with a supportable crust beneath the new snow will allow for the safest travel. Stick to low-angle terrain that is not connected to steep overhead hazards if you plan on recreating on the north side of the compass.

     

     

    (2/14/2026)

    This is one of multiple natural and human-triggered slides that occurred on Saturday (2/14) in the Six-Mile area. These slides likely failed on a buried layer of surface hoar. Around 8" (20cm) of fresh snow fell in this location from Friday into Saturday.

Avalanche Discussion

Storm totals include 9" of settled snow at Tunnel Ridge in the Flathead Range,  and around 0.5" of SWE in the central and northern Whitefish Range, and at Noisy Basin in the Swan. This event was accompanied by blustery south-southwest winds that transported the low-density snow onto leeward slopes.  Despite the relatively modest precipitation, the sensitive, widespread buried surface did not handle the additional load well.

Observations were limited, but we received reports of an avalanche in the southern Whitefish Range (image) and of multiple natural and rider-triggered slides in the Swan (Observation). Widespread cracking, collapsing, and shooting cracks were noted in multiple locations (Observation,  Observation, Observation).

The unusually widespread layer of surface hoar formed during the dry weather of the second and third weeks of January remains concerning. This layer has gained little to no strength on the shady aspects, where it is best preserved. Its weakness is evident in the number of signs of instability this layer shows during and after a loading event, such as the recent storm. 

Prior to the recent snowfall, clear conditions allowed another crop of widespread surface hoar to form, which is now buried under a few inches of snow. This could become our next weak layer and, with snowfall in the forecast, affect snowpack stability as early as today, or sometime this week.

 

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