Bollettino valanghe

Swan Range

Flathead Avalanche Center
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Pericolo valanghe

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

In sintesi

The storm has departed, leaving behind fresh slabs that a rider can trigger. These features become larger and more dangerous as you gain elevation, especially where you encounter wind-blown snow. An incoming storm later today and into Monday will increase the hazard.

Problemi valanghivi

  • Storm Slabs

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

    The Friday/Saturday storm deposited up to a foot of snow at mid-elevations and more in the Alpine. Expect to find fresh slabs on all aspects that will increase in size as you gain elevation. These features formed on various surfaces, including recent low-density snow, scoured hard windboard, crusts, or hard and soft slabs of varying ages. 

    Fresh slabs will be most dangerous in locations where the wind drifts the snow into thicker slabs near ridgelines, below saddles, and on cross-loaded terrain features. 

    Slabs can be identified by a denser snow surface, which may crack beneath your or your machine's weight, indicating you have found a sensitive slab. Choose lower-angle terrain to limit being surprised.

    (12/28/2024)

    Crown of a skier-triggered soft slab in the Canyon Creek area, just outside the boundary of WMR.

  • Persistent Slabs

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

    The recent storm added weight to a weak layer formed in early December, now buried 2-4+ feet deep. Above this layer, one or more additional crusts with associated weak layers are found in some locations.  A rider's chance to trigger a slide on these buried layers increases during or immediately following loading events. These will be more likely in areas favored by recent snowfall or wind-loading.

    Most avalanche activity on the early December buried weak layer has been generally limited to north and east-facing slopes.  These slopes will be getting tested the most with today's wind-drifted snow.

    For a safer experience, choose lower-angle terrain or stick to a south or southwest aspect where the weak layer is not as well developed. 

    (12/28/2024)

    This snowpit on an upper-elevation northerly slope showed propagation with moderate force. The failure layer is a thin layer of small-grained facets 50 cm below the surface.

    Photo: Jeremy Primmer

Avalanche Discussion

The Friday/Saturday storm lost strength but not before dropping up to 1.5 inches of water at mid-elevation SNOTELS. Warm temperatures resulted in modest snow totals, but we assume upper-elevation locations picked up a foot or more settled snow in many places. The new and wind-blown snow has had time to settle, and we have decreased the hazard for Sunday except for the Flathead Range. Another storm system moves into the area this afternoon, with the avalanche hazard rising overnight and through Monday. This system may wallop the Swan Range. 

Saturday, a rider accidentally triggered an avalanche on a southwest aspect of the Skook Chutes in the southern Whitefish Range. The slide failed on a crust a foot below the surface, resulting in a crown 80 feet wide. The party has ridden southerly slopes before this with no signs of instability. The individual did not get caught or carried by the slide.

The fresh storm snow will likely sluff on steep slopes favored by snowfall. The associated danger is not enough to list as a problem but could knock you off your feet in large terrain or long-running gullies. Limit your time above terrain traps and use sluff management techniques to manage this issue.

Downloaded the app yet? 

You can now access our region's forecasts, observations, and weather data directly from the Avy App (IOS; Android). Many features are accessible offline, so you can doublecheck danger ratings and travel advice on the drive to the trailhead or in the backcountry. 

Events and Education:

Want to start your New Year on the right foot? Sign up for a Partner Rescue Clinic for motorized Riders on January 4. Check out our calendar for other upcoming events. 

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