Boletín de aludes

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Peligro de aludes

Tue
Alta montaña
2 · Moderado
Límite del bosque
1 · Débil
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 6 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Isolated wind slabs exist in exposed, upper elevation terrain. These slabs will be relatively small but could knock you off your feet and carry you downslope. Be alert to the consequences of being caught in a slide in the terrain you are traveling in. If the clouds clear earlier than expected this afternoon, small sluffs involving the new snow will be possible on very steep, rocky slopes that directly face the sun.

Problemas de aludes

  • Wind Slabs

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

    Yesterday, a rider in the Sawtooths reported intentionally triggering a wind slab formed from the 4-6" of snow that fell on Saturday. It failed 15-20' wide on a slick crust, and ran downslope 1,000'. Just north of this zone, in the Banner Summit area, skiers triggered two small avalanches involving Saturday's snow. The first, a loose dry avalanche, was triggered intentionally with a cornice from the top of their intended line. It picked up speed quickly and ran to the bottom of the slope. The second slide (pictured at right) happened lower on the slope as the party descended. It broke slightly above the skier and carried them downslope an estimated 100 feet. 

    These two types of slides are the same type that you should be on the lookout for today. Where you are finding dry, light powder to ride, be alert to the possibility of triggering a sluff, particularly where the new snow is sitting on a crust. In areas where the wind has built slabs, or where the settling of the new snow has formed a slab, look for signs of instability such as cracks shooting out from your skis or board. Neither of these types of slides is likely to bury you, but as happened yesterday, they could easily knock you off your feet and send you downslope. Be conscious of the consequences of being caught in a slide in the terrain you are traveling in. 

    ADDITIONAL DISCUSSION:Today should be mostly cloudy, but the weather forecast has been wrong before. If the sun pokes out from the clouds for long, I'd expect to see loose snow sluffs on very steep slopes that directly face the sun. These will be small, involving only the new snow, but may travel downslope quickly thanks to the crust underneath. 

Avalanche Discussion

Last week's unseasonably warm temperatures (come on, it's not even mid-March yet!) had us worrying about wet snow problems, but new snow on Saturday and cooler temperatures brought a return of avalanche problems more common in the winter. Yesterday, skiers and riders triggered small avalanches in our Banner Summit, Galena Summit and Eastern Mtns, and Sawtooth and Western Smoky Mtns Forecast Zones. All of these slides involved new snow that was poorly bonded to the older snow underneath. The problems that you'll be dealing with today will be the same variety as the ones that skiers and riders encountered yesterday. Fortunately, these types of instabilities are relatively straightforward to identify and manage. Here's what to be on the lookout for:

  • Wind-drifted snow: You'll find wind slabs in upper elevation terrain, adjacent to terrain features that force the wind to slow down and drop the load (snow) it is carrying. Common places are near ridgelines and mid-slope features such as ribs and gullies. If you push on these with your skis or sled, do you get any cracking? If you dig a quick pit with your hand and pull on the slab does it detach easily from the underlying snow?
  • Settling new snow: The slide that caught a skier yesterday appeared to have failed in an area without wind loading. As the new snow settles it can form a soft slab in its own right. This type of slab is less likely than the wind slab problem but is still something to watch out for. As with wind slabs, look for cracking in the new snow as an indicator that slabs are poorly bonded to the surfaces underneath. 
  • New snow sitting on frozen crusts: Crusts formed on many slopes during last week's warm and sunny days. Any snow that you get moving has the potential to quickly travel downslope over these crusts. This is a problem that you are most like to trigger yourself, but if we get an hour or two of sun this afternoon, we may see these beginning to initiate naturally.

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