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
3 · Notable
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó last year. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Warm overnight temperatures will make it possible for a rider to trigger wet snow avalanches on steep slopes.  Falling cornice and small surface slides can trigger very large avalanches on buried weak layers.  Avoid traveling below obvious hazards like large avalanche paths or glide cracks

Problemas de aludes

  • Wet Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1.5–3

    Sustained warm temperatures, rain, and sunshine have saturated the snowpack well below the surface. Liquid water can destabilize weak layers and cause wet slab avalanches that break at various depths including near the ground. Wet surface snow may sluff naturally on steep and rocky slopes or readily under your feet or machine.

    Upper-elevation slopes facing NW-N-NE-E could be particularly troublesome following a night of 40+*F in the alpine.  Lower and middle-elevation slopes have already been worked over and are less likely to slide. However, you may still be in striking range of large and long-running avalanches from above. 

    Avoid traveling on or under steep slopes especially during the heat of the day. Debris from wet snow avalanches can trigger larger slides on buried weak layers. 

    (3/1/2025)

    Possible wet slab avalanche.  This slide failed on a buried weak layer after prolonged warm temperatures.

    Photo: Tyler Kitch

  • Cornices

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–3

    Cornices have been building all winter and loom above the leeward side of ridge lines. Prolonged, above-freezing temperatures will continue to weaken cornices and make failure likely.  It is possible for falling cornice to trigger very large avalanches on the slopes below.

    Cornice cracks are a sign of an impending failure. Always give cornices a wide berth when traveling along ridgeline and don't dawdle on the slopes directly below. 

    Prolonged warm temperatures in the alpine will cause cornice to weaken and release.  Cornice fall can trigger very large avalanches.

    Photo: Flathead Avalanche Center

  • Glide Cracks

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–3

    Meltwater draining from the snowpack can lubricate the ground surface, increase glide, and ultimately cause large and destructive glide avalanches.  Some glide crack may be obscured by the abundant march snowfall. Cracks have been reported on all aspects and elevations but are concentrated on solar aspects at mid-elevations. The northern Swan has been a hot bed of glide activity. 

    Glide avalanches are notoriously difficult to predict.  Don't push your luck as these avalanches will involve the entire season's snowpack. Avoid traveling on or below slopes where this hazard is present. 

    (3/1/2025)

    This glide crack succumbed to the heat of the day Saturday, 3/1. The resulting avalanche was very large (D3).  

    Photo: Flathead Avalanche Center

Avalanche Discussion

The big news this morning is the overnight temperatures in the alpine. Yesterday (Wednesday), upper-elevation sites recorded temperatures near or above 50*F. Clouds moved in during the afternoon and trapped warm air in the mountains. As of 0400 this morning, stations at Aeneas Ridge and Sperry had not cooled off at all (they have since dropped several degrees but are still near or above 40*F). Today should be the last day of above average temperatures.  An approaching cold front will hopefully cool things down into the weekend. Until then, wet snow, falling cornice, and slabs failing deep in the snowpack or at the ground remain a concern.

Observations from Wednesday continued to document the carnage from a natural avalanche cycle that occurred last weekend. Check out these observations from the Flathead Range and Condon. Some of these avalanches failed on buried weak layers. We removed the Persistent Slab problem from today’s forecast since the hazard of natural or triggered avalanches on buried layers is communicated in the current Wet Slab and Cornice Fall problems.

 

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