Bollettino valanghe

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Wed
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
4 · Forte
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In sintesi

Large, destructive natural and human-triggered avalanches are almost certain to occur. Avoid all avalanche terrain. Stay off of and out from below steep slopes—slopes steeper than about 30 degrees. Avalanches may be triggered remotely—from gentler terrain above, below, and to the sides of steep slopes.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Certain
    Dimensione
    2–3.5

    Many flavors of large destructive avalanches—wet, dry, slabs, loose, wind-driven, etc.— are likely to release on their own today. The travel advice is simple: stay out of the way. Read the Forecast Discussion below for details on specific avalanche problems other than the Persistent Slab problem described here.

    What is it? Powerful, 2-5 foot thick avalanches are a near certainty. Snowfall, wind-blown snow, and rain will overload the buried weak layers (sugary facets or crust + facet combinations) that produced hundreds of avalanches and tragically resulted in an avalanche fatality in recent days. Many slides will release naturally, on their own. Some avalanches will probably be over 1000' wide. 

    Where is it?  Given that we've received snowfall all but one day since February 26th, the slabs exist on almost all slopes that have not already avalanched. Many of the slopes that avalanched last weekend have "reloaded" with fresh, dense slabs. The weak layers are also widespread.

    How can you recognize it? Avalanche terrain includes slopes steeper than about 30 degrees and areas below steep slopes. 

    How can you manage it? Stay off of and out from beneath slopes steeper than 30 degrees. Persistent weak layers can fail unpredictably and break significantly wider, deeper, and higher on slopes than you might expect, producing much larger avalanches. Smaller loose snow and storm slab avalanches can trigger larger persistent slab avalanches lower on slopes. You could remotely trigger avalanches from gentle terrain far above, below, or to the sides of steep slopes. 

    (3/11/2023) This very large persistent slab avalanche was observed in the Boulder Mountains. It failed over 3,000' wide, wrapping around S-SE-E-NE aspects between 10,000' and 10,800'.

Avalanche Discussion

We could face 7 different avalanche problems today: persistent slabs, deep persistent slabs, wet slabs, wet loose, dry loose, storm slabs, and cornice. How do you manage something that complex? You don't. Avalanche conditions will be "predictably unpredictable." What should you expect to see as you move up in elevation in the mountains today?

  • Lower elevations: Rain will likely produce natural wet loose avalanches involving the snow that has fallen in the past two weeks. Some wet slides will involve only the wet snow near the surface, and some will probably gouge down to the ground or crusts near the ground, taking out all or most of the snowpack. Areas with a deeper snowpack could produce wet slab avalanches. Once you climb above the rain line, you're likely to see or trigger persistent slab avalanches and relatively small storm slabs. Remember that large avalanches releasing in middle or upper elevation terrain can run "full track", impacting lower elevation locations. 
  • Middle elevations: You'll be dealing with the persistent slab avalanche problem described above and dense storm slabs involving the snow from yesterday, last night, and today. Natural loose snow avalanches (dry and "damp") are likely on very steep slopes and make great triggers for larger persistent and storm slab avalanches. 
  • Upper elevations: Moderate winds will form dense, meaty slabs in exposed terrain. The wind-loading will make natural and human-triggered persistent slab avalanches almost certain to occur, and deep persistent slabs (monster 4-8 foot thick slides) are possible. Storm slabs are likely in all sheltered avalanche terrain. The unrelenting snowfall and warm temperatures are increasing the chances of large cornices breaking on their own or with the added weight of a person or snowmobile.   

Be sure to give yourself a large safety margin if you're out playing today. Stay clear of overhead avalanche hazards. Have fun, be safe, and enjoy Mother Nature's show. 

Regioni coperte