Boletín de aludes

Northwest Mountains

Crested Butte Avalanche Center
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Peligro de aludes

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

Lo esencial

You can trigger slab avalanches on previously drifted terrain features.  The most likely locations are leeward, upper-elevation slopes below ridgelines and cornices; however, you could encounter one in a concave feature on windward aspects.  Identify and avoid stiff, pillowy-looking snow deposits at upper elevations to reduce your chance of triggering a slab avalanche.  Loose snow avalanche hazards exist if you travel through wind-protected terrain on the north half of the compass.  Most loose avalanches would be small but big enough to drag you into rocks or trees.  Slope angles under 35 degrees are unlikely to produce loose avalanches and offer a less risky terrain choice.

Problemas de aludes

  • Persistent Slabs

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

    Since 12/9, several northwest-to-southwest wind events formed slabs around a foot thick. These wind-drifted slabs are most commonly found at higher elevations below leeward ridgelines and rollovers on east and northeast-facing terrain. They can also be found around the northern half of the compass in a few concave terrain features that collect drifting snow, such as gullies. These slabs are often hard and difficult to manage, breaking unpredictably and with inconsistent feedback underfoot.  Because many of them formed over weak, faceted snow, instabilities are slow to heal.  Assess recent wind-loading patterns and consider avoiding previously wind-loaded terrain features, especially in high-consequence terrain.   

     

     

  • Loose Dry

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–1.5

    In terrain that has been protected from the sun and wind, the snowpack is growing increasingly weak and cohesionless.  Weather conditions make human-triggered sluffs larger and more common as the shallow snowpack facets.  These point-release instabilities are relatively small and easy to recognize. Still, they can spell trouble by pushing you into trees, rocks, or gullies, especially in long, steep terrain where they gain more volume.  Use sluff management techniques or move to less consequential, lower slope angles to manage the problem. 

Avalanche Discussion

The Persistent Slab problem on wind-loaded slopes presents a greater hazard as the potential size could bury or hurt you.  Slabs are relatively small in size compared to typical Persistent Slab problems, but once in motion, they can gouge into the weak snowpack and accumulate more mass.  Over the past week, several natural and human-triggered avalanches have been documented on leeward terrain features.  On Wednesday, forecasters experienced cracking and collapsing in stiff, drifted snow along the top of Schuylkill Ridge, which suggests slabs remain sensitive to a person's weight.  You are more likely to encounter this problem in the Northwest Mountains as more snow has accumulated recently; however, we have far less data from the Southeast Mountains.  Evaluate the local wind-loading patterns and steer away from previously drifted terrain features to hedge your bet.

The snowpack continues to weaken as it remains shallow and seasonably cold.  The faceting process and previous avalanche activity from the Thanksgiving cycle removed most slab structures at lower elevations, leaving behind a soft and often cohesionless snowpack on the north half of the compass.  Observers have noted triggering loose avalanches on steep, sun/wind-protected slopes that take most of the snowpack out (ob 1, ob 2, ob 3, ob 4).  The simplest way to manage this problem is through slope angle.  Slopes around 35 degrees or less are unlikely to loose avalanche and provide easier riding conditions in an unsupportive snowpack.  As slope angles near or exceed 40 degrees, expect loose snow avalanches to become likely.

Events:  Our first Fireside Chat of the year is this Sunday (12/22) at 6 p.m. at the Eldo.  Andy Sovick(Beacon Guidebooks/OnX Maps) will chat about Maps and Tour Planning.  These events are free and open to all.

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