Boletín de aludes

Flathead Range & Glacier NP

Flathead Avalanche Center
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Peligro de aludes

Fri
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó last year. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

The avalanche danger is increasing today as new and drifted snow accumulate. Dangerous conditions will develop if accumulations reach forecasted totals. Avoid steep slopes with more than about 8 inches of new and drifted snow. Be alert for changing conditions and pull the plug if you see shooting cracks or recent natural avalanches. 

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–2

    Northeasterly winds will load drift snow onto southeast though southwest to northwest slopes at upper elevations today. The winds may also crossload chutes on northerly and easterly slopes. Freshly-formed slabs will grow larger and more sensitive to the weight of a person or skier as the day progresses. The slabs will be isolated at mid elevations.

    This hazard should be relatively easy to identify and avoid today. Stay alert for snow that feels dense or cakey and cracks around your feet or machine. Scalloped or etched snow surfaces are also reliable clues. Slopes where the air is full of swirling snow are being actively loaded; these may be the most sensitive to your weight. Hard slabs - where you don't sink into the new snow by more than an inch or so - are poor candidates for slope cuts because they tend to break above you.

    (1/30/2025)

    Shooting cracks in wind-etched surfaces are a clear sign of today's hazard.

  • Loose Dry

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    On very steep slopes where the new snow hasn't been consolidated by winds, you can trigger loose snow avalanches. Most will be small and run in the new snow or on the old snow surface. In long, continuously steep terrain, however, these sluffs could be larger and more dangerous. They may gouge into recent snow and run far on the melt-freeze crust from this weekend, entraining more snow and making them difficult to escape. Brief periods of direct sun will increase the likelihood of natural slides.

    You can reduce the your exposure to this hazard by riding on slopes that aren't steep, confined, and/ or above terrain traps. If you do choose this terrain, veer off the fall-line or traverse to the side every few turns, to let your sluff pass before it builds up and knocks you off your feet or machine. Watch for overhead hazards if sunshine appears, which can quickly trigger loose dry sluffs."

    Long running, dry loose sluffing in steep, alpine terrain. 

    Photo: Michael Reavis

Avalanche Discussion

Old Man Winter seems to be raging against the light, as he often seems to do in early April. A storm Tuesday dumped 2 feet of snow in Noisy Basin and 5 to 13 inches elsewhere in the region. Another 3 to 5 inches has accumulated overnight, with about double that expected today as a cold front sweeps east from the Continental Divide. Accompanying today's snow will be gusty northeasterly winds. The recent and new snow sits on a supportable melt-freeze crust that formed over the weekend.

That combination of new snow and winds will increase the avalanche danger today. The primary concern will be wind slabs on usually-windward, upper-elevation slopes. Loose dry snow avalanches will be a hazard on slopes where the snow remains unconsolidated by the wind. The size and likelihood of both flavors of slides will increase through the day, before the snow and wind shut off behind the cold front passage. That looks to be roughly sunset. I will note here that my confidence in today's forecasted snow totals isn't high; models often have a hard time capturing the speed of cold fronts and there's a lot of variation in the model outputs this morning. Basically, we'll get less snow if the front is faster than forecast but more if it stalls. 

 One other uncertainty this morning. Recent years have often seen a spike in avalanche incidents and accidents the first few days of April, following late-season storms like this. The April Fools slides typically release on thin layers of near-surface facets that develop during extended dry periods in March. We most certainly didn't have a dry March. But the wet snow buried Tuesday may have recrystallized (brief description; geek fest article). Shooting cracks, whumpfing collapses, and propagation in large column tests are good signs a persistent slab structure has developed. Be alert for slides that propagate wider than expected. Definitely retreat to less steep and exposed terrain if you're seeing theses conditions. 

Tonight, skies will clear and lows will dip into the single digits. Tomorrow will be sunny, and like it or not, Old Man Winter will have to go gentle into that good light. That translates into potentially great late winter riding. However, today's hazards will linger, so plan objectives that have multiple options, including a conserative one if conditons are more dangerous than you expect.

For years, the avalanche community has worked to understand and address the human factors that influence decision-making in the backcountry. With decades of research as their foundation, Sara Boilen and Ian McCammon are developing an open-source tool to help individuals mitigate risk in avalanche terrain. The project's first stage involves interviewing backcountry recreationalists who have been traveling in avalanche terrain for at least one season. All participants will be entered to win amazing raffle prizes (from Jones Snowboards, BCA, and more!). If you’re curious about being involved, please take 1-2 minutes to fill out our interest survey!

 

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