Boletín de aludes

Flathead Range & Glacier NP

Flathead Avalanche Center
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Peligro de aludes

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

Lo esencial

You can trigger slabs that break 1 to 3 feet deep on weak layers where wind has stiffened the overlying snow.  Stay alert for signs of instability - like whumpfing (collapsing sounds) and cracking. If you encounter these, step back to lower-angled, simpler terrain. Low-density snow may sluff on very steep slopes, particularly those receiving direct sun.

Problemas de aludes

  • Persistent Slabs

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

    Buried by February's powder are layers of weak snow that formed during Dry January. While these layers are widespread, the slopes where you can trigger a slide are isolated. These may break 1 to 2 feet deep and will involve enough snow to bury or injure a rider. Those consequences are serious enough to influence terrain choices and route selection today. 

    Be alert for - and avoid - steep slopes where wind has stiffened the surface snow into cohesive slabs. This stiffening may be subtle; the slabs may only be slightly denser than snow on surrounding slopes. Or it may be obvious; the snow surface may be etched and scalloped by the wind, or a slope may be littered with dunes, drifts, and pillows of hard snow. Potential trigger points will be most common on slopes with convexities or variable snow depths. 

    Signs of instability have been concentrated in the Whitefish Range, where multiple groups continue to report collapsing (whumpfing), shooting cracks, and a remotely-triggered avalanche. These have been most frequently reported on southerly aspects. We have fewer reports of these signs of instability from our other zones.

    (2/11/2025)

    A good example of the terrain where you might trigger a slide on an old, buried weak layer today. You can see a crown and debris from large natural avalanche on looker's right. This slide likely broke on older, weaker snow.  The slope shows the effects of wind with a cornice near the ridge and variable textures in the snow surface. There is also evidence of sluffing in the center of the face. 

    Photo: Kaleb Retz

  • Loose Dry

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

    On very steep slopes, you can trigger sluffs that entrain the recent low-density snow and even gouge into older, underlying facets. That makes them harder to escape. They can be surprisingly hazardous if you get surprised and swept off your feet or machine, particularly in long, confined chutes. To avoid this problem, stick to lower-angle terrain where sluffing will be limited. If you do choose to ride in steeper terrain, pick lines that aren't above terrain traps, like cliffs, gullies, and trees. I expect this hazard to diminish as the recent snow settles. The hazard exists on isolated slopes at low elevations. 

    Triggered and natural sluffs are most likely today in areas that receive direct sun. Clumps of snow falling off trees and rocks  - or started by your board or machine - can release rollerballs that fan out and pick up snow as they move downslope. Be mindful of steep slopes when they're in direct sun. 

    (12/2/2024)

    Radiation can trigger small point release avalanches in sunny, steep, rocky terrain today.

    Photo: Flathead Avalanche Center

Avalanche Discussion

January's dry conditions continue to recede into the rear view mirror. But its legacy - layers of weak snow - persists. February's storms have slowly loaded these weak layers without prompting widespread instability. The hazard of triggering large avalanches lingers, though it's mostly isolated. With warmer temperatures, February's snow will settle and consolidate. That may make the slabs above these weak layers more sensitive to the weight of a rider or snowmachine. 

These aren't hide-under-the-bed conditions. But they are sleep-with-one-eye-open conditions (cue Metallica). Pick travel routes that minimize overhead hazard. Play on slopes with relatively uniform snow cover and few convexities. Most importantly, be alert for signs of instability and changing conditions. If you encounter shooting cracks, or loud whumpfing collapses, or trigger slabs on inconsequential slopes, step back to simpler, lower-angled terrain.

Upcoming Events: Check out our calendar and sign up now!

  • February 20-22nd: Avalanche Safety: Introduction to Avalanches Human Powered for Skiers and Snowboarders - register here
  • Feb 26th - Pint Night at Blackstar with donations going to Flathead Avalanche. State of our Snowpack presentation at 7 pm! 

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