Bollettino valanghe

Banner Summit

Sawtooth Avalanche Center
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Pericolo valanghe

Fri
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Limite del bosco
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Sotto il limite
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In sintesi

Sunshine and warm temperatures could produce wet loose avalanches. These slides are most likely on very steep slopes that directly face the sun and are sheltered from the wind.

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    There are two varieties of wet loose avalanches to consider today: 

    • Wet loose - new snow: Dozens of natural wet loose avalanches occurred in the last couple of days. Many of them initiated in rocky, alpine terrain as the warmth from direct sun weakened fresh snow at the surface. Today, this problem will start on slopes that face E-SE and work its way around through S-SW and W as the sun tracks across the sky. Use fresh-looking, recent, wet loose activity as an indication of where these slides are most likely again today. 
    • Wet loose - old snow: At lower and middle elevations, deeper, gouging wet loose avalanches are possible. These slides are most likely later in the afternoon as the ice crusts at the surface turn to mush. You're most likely to encounter these on very steep, wind-sheltered slopes.  If you can easily push your foot or ski pole through much of the snowpack, or if the tail of your sled or bike drops deeply when you goose the throttle, you have likely found a snowpack where this type of problem is possible.

    Note how the snow surface is changing. If it's easy to make snowballs, or you are falling through crusts into slushy snow underneath, the chance of wet loose avalanches is increasing. You can greatly reduce your risk by sticking to colder snow on more shaded slopes or by traveling earlier in the day when the snow surfaces are firm.

    ADDITIONAL DISCUSSION:Tuesday, an experienced party intentionally ski cut a small slab avalanche on Copper Mountain. You might find similar conditions today on isolated slopes. Look for cracks shooting from your skis or board as an indication that you've found a sensitive slab. See the Forecast Discussion below for more details.

Avalanche Discussion

It looks like we can expect another beautiful day in the mountains. It will be cooler today and tomorrow which will help curb the chances of deeper, gouging, wet loose avalanches. We've also had two days of direct sun to help mitigate the hazard on slopes most prone to sun-induced wet loose avalanches involving new snow that fell over the weekend. These wet avalanche issues, although less likely today, are still worth paying attention to and should be at the front of your mind when choosing a time and place to enjoy the mountains.  

As you turn to drier, cooler aspects or climb into more wind affected, alpine terrain, there are a few other problems to keep in mind: 

  • Soft slabs: Yesterday's wind built small, sensitive drifts in alpine terrain. A skier in the Central Sawtooths was able to trigger one of these pockets yesterday, and they will likely be sensitive to your weight again today. In the Banner Summit area and far northern Sawtooths, skiers triggered three small slab avalanches since Sunday. These avalanches shared the following characteristics: SE-E-NE aspects, slopes approaching 40 degrees in steepness, near or above about 9000' in elevation, and about 8-12" of new or windblown snow sitting above a subtle crust with a thin layer of small facets above it. These slides have not been big enough to bury people, but they can definitely push you around.  
  • Cornices: These huge chunks of snow become increasingly unstable as warm temperatures and direct sunlight cause them to sag and bend. Tuesday, several small cornice chunks peeled off during the day, triggering dry loose avalanches on the slopes beneath them. Large or small, be alert to the hazard cornices pose if you're traveling below them or on ridgelines. It is very difficult to accurately determine where a ridgeline's "terra firma" stops and the cornice starts; almost every avalanche professional has a story about a close call or accident they've had involving cornices. 
  • Dry loose - new snow: We observed several recent small, natural sluffs that failed on steep, shady NE-facing alpine slopes. Many appeared to be triggered by small cornice chunks falling onto the slopes. These sluffs probably won't be large enough to bury people, but they can quickly pick up speed and knock you off your feet or sled and carry you places you don't want to be.  As with the wet loose problem described above, this type of slide is most likely in areas that received more than a few inches of new snow recently. 

Another storm is on tap for the weekend and it looks like we've got a good chance to hit "refresh" on the ski conditions. Weather models are at odds with one another when it comes to snow amounts and distribution. I'm hesitant to go out on a limb just yet, so check back tomorrow for a more detailed forecast for the weekend. With the new snow, expect to also hit "refresh" on our avalanche problems. The chances for small slab and loose snow avalanches will increase near the tail end and shortly following the storm. 

 

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