Boletín de aludes

Flathead Range & Glacier NP

Flathead Avalanche Center
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Peligro de aludes

Sun
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 7 months ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Your safest option for great weekend riding will be found on low-angled slopes sheltered from recent winds. Riders have triggered large avalanches on buried weak layers during the last 3 days. Recent avalanches, audible collapses, and shooting cracks are all good reminders to step back from steep terrain. 

Problemas de aludes

  • Wind Slabs

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

    Fresh wind slabs formed on Thursday and Friday and may remain sensitive to the weight of a rider. Today's light to moderate southwest winds may continue to build slabs along ridgelines and downwind from saddles or other prominent terrain features. 

    Recently formed cornices, textured surfaces, and hard-over soft snow will help you identify slopes with wind-drifted snow. Cracks that shoot out from your feet or machine are clear indicators that these slabs can be triggered by a rider on steep slopes. Terrain sheltered from the wind will continue to provide excellent snow quality and a greater margin for error.

    Slabs may be larger and easier to find in the Flathead Range and near the Continent Divide, as these areas received more recent snow and wind. Even a small slab of wind-drifted snow could trigger a deeper, more destructive slide failing on a persistent weak layer (see Problem 2).

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1.5–2.5

    Weak layers buried 1-3 feet below the surface have been the culprit in two recent human-triggered avalanches in the Southern Whitefish Range. Avalanches breaking on these layers may not give obvious signs of instability before failing, and could propagate much wider than expected.  It may be possible to trigger large avalanches remotely from connected low-angle terrain above, beside (see image), or below start zones. 

    Digging into the snow may help identify these layers and assess their sensitivity. The challenge is their high spatial variability—you may not find anything concerning in a test pit, but that doesn’t mean the slope you’re eyeing lacks the ingredients for a dangerous avalanche. Increase your safety margin by limiting exposure to steep, open, and unsupported slopes. Lower-angled slopes without overhead hazards or terrain traps are your safest option.

    IF and when the sun comes out today, small sluffs or cornice fall could trigger larger avalanches on buried weak layers. 

    (1/9/2026)

    A small skier-triggered avalanche that was triggered remotely, east of WMR on 1/9. We supect this avalanche failed on a persistent weak layer.

    Photo: Anonymous

Avalanche Discussion

It appears that we are back on a warming trend. If we receive more sun and warmer temperatures than expected, anticipate greater potential for loose dry sluffs and crumbling cornices. Natural sluffs are most likely on very steep, treed, and rocky slopes that tilt towards the sun. Recent snow and southwest winds have grown cornices above slopes facing NW-N-NE-E-SE. These may start to weaken or fall if we experience sustained sunshine and/or warm temperatures. 

Any tumbling snow has the potential to trigger larger avalanches on buried weak layers. Facets - some of them huge - have been found resting on various crusts formed in December. The real bummer is that they are not always easy to find, which can make your decision-making difficult. Josh and I came to this conclusion as we analyzed a recent skier-triggered avalanche near WMR. We found large facets at the crown face, but could not find this layer (or get propagating results) immediately uphill or adjacent to the flank. We both acknowledged that we easily could have gotten surprised on this slope, even if we had dug a pit before skiing. This almost slope-scale variability is all the more reason to widen your safety margins.

Mike and I traveled to Stryker Ridge on Friday, where we were more reliably able to find facets buried roughly 1.5 feet deep (on the presumed Christmas interface) and got propagating test results.  A second skier-triggered avalanche occurred near WMR yesterday (Friday). FAC is sending a field team to this location today to take a closer look.

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