Bollettino valanghe

Flathead Range & Glacier NP

Flathead Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
1 · Debole
Sotto il limite
1 · Debole
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In sintesi

Warm and sunny conditions may develop wet snow avalanche problems on slopes receiving direct sun. Riders could trigger fresh, thin slabs of wind-blown snow in steep, exposed terrain. Slopes sheltered from the sun and wind will hold drier, safer snow. 

Problemi valanghivi

  • Loose Wet

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

    This morning, a temperature inversion has left mountain readings just below freezing. Sustained sun and warm air should break down the melt-freeze crust formed yesterday, resulting in moist surface snow. The chance of natural and rider-triggered slides will increase throughout the day. These should remain relatively small due to the various crusts underlying the surface. The exception will be in large terrain features or long-running gullies.

    Snow falling from trees or the onset of the surface crust breaking down indicates that this problem may be developing. If you want to play on the sunny side, utilize various aspects to stay ahead of the sun. Plan your exit so you do not travel below sun-baked slopes later in the day. Riding on shady slopes will offer drier, softer snow. 

       

    (3/14/2024)

    Rollerball activity began during the afternoon on steep rocky and treed solar slopes.

    Photo: Rob Millspaugh

  • Wind Slabs

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

    Southwest winds continue to blow and transport the small amount of loose surface snow available on windward aspects. Fresh slabs will be thin and confined to slopes immediately downwind of exposed upper-elevation terrain, such as the top of chutes, couloirs, and behind prominent terrain features. These may disguise older slabs formed over the previous days.

    Wind-stiffened snow will feel denser and will not allow your boards or machine to sink as deeply as snow found in protected locations. The surface may have a rippled texture with a dune or pillow-like look. Cracking indicates that you have found a sensitive slab. Slopes sheltered from the wind and sun will hold softer snow. 

    (1/13/2025)

    Jan 13th, 2025: Recent winds cross-loaded snow onto the lee (easterly) side of this ridge. 

    Photo: Ted Steiner

Avalanche Discussion

Wednesday's mostly sunny conditions allowed snow-covered trees to begin melting and initiate tree bombs on sunny aspects. I enjoyed a day off spinning laps at WMR, where the trees started dripping mid-morning and soft bump skiing developed in the afternoon. Unfortunately, this morning (Thursday), you will encounter a thin, breakable melt-freeze crust on slopes exposed to yesterday's solar. Overnight mountain temperatures only cooled slightly and are hovering just below freezing in many locations. Today's temperatures could be five or more degrees warmer than yesterday, with a similar amount of sunshine. Triggering a slide in the moist surface snow could become possible once the surface crust breaks down.  These should be harmless except in large terrain features or slopes that end in terrain traps where the debris can pile up deep.

We are keeping Wind Slabs on the problem list due to elevated winds at upper-elevation weather stations. Speeds increased overnight, with most stations above 6500 feet blowing at 20+ mph with gusts into the 30s. Aeneas Ridge is windier with 30+ mph and gusts to 54. However, there is not a lot of snow available for transport due to the lack of recent snowfall, rime and freezing rain crust development, and yesterday's melt-freeze crust. This will inhibit slab development, keeping fresh features relatively small and confined to the most exposed terrain. 

Glide cracks continue to open and fail throughout the forecast region. Wednesday, we received photos from a dedicated observer that show three large gaping cracks in the same neighborhood on the Swan Front (photo1, photo2). Further south in the Swan, Rob saw a developing glide crack (photo). A party in the central Whitefish Range noted a large portion of a glide crack that recently failed (photo). Another group reported glide cracks and failure in the Mission Mountains on Sunday (photo1, photo2). Glide avalanches are poorly understood, and the best way to mitigate this hazard is to not recreate above or below these features. 

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