Bollettino valanghe

Soldier & Wood River Valley Mtns

Sawtooth Avalanche Center
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Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

In the western part of this zone (Soldier Mtns and Dollarhide Summit area), the size and chance of triggering avalanches will steadily increase as today's warm, intense storm progresses. Tricky, dangerous conditions will develop—several types of natural and human-triggered avalanches will become likely. The danger will rise to CONSIDERABLE by this evening and could spike overnight. Carefully plan your day to be out of the mountains before dark. 

In the drier mountains near and east of HWY75: less new snow is expected, but you still may be able to trigger large avalanches involving all the snow that fell in February. Read the Forecast Discussion for details. 

Problemi valanghivi

  • Storm Slabs

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

    Above the rain line, different types of natural and human-triggered avalanches will become likely. Slab avalanches are most likely to release where it's "steepest and deepest": on slopes steeper than about 35 degrees, where at least 6" of snow has accumulated. The slabs will grow steadily through Monday morning. On some slopes, crusts and / or weak snow exist beneath the new snow; avalanches could be easy to trigger and may break wider than you expect. A couple types of slab avalanches to watch for: 

    • Storm Slabs: The dense, damp storm snow will forms slabs on most slopes, including slopes that are completely sheltered from the wind. These avalanches could be big enough to catch, carry, and injure people. 
    • Wind Slabs: At upper elevations, the new snow will be less dense, perfect for expected moderate to strong winds to form wind slabs up to 2 feet thick. You may find some wind slabs at middle elevations. Watch for fresh drifts and slabs below ridgelines, on the sides of cross-loaded gullies, and on aprons at the bottom of steep alpine cirques.

    Cracks shooting out from your sled or boards are a clear sign you've found a slab and should stick to gentle terrain to avoid trouble. Natural loose snow sluffs or cornice fall could also trigger slab avalanches; minimize the time you spend in the runouts of large avalanche paths. 

    Avalanche conditions and stability will deteriorate this afternoon and tonight. Don't assume the avalanche path you played in this morning is still safe near dark. 

    Additional Discussion - Persistent Slabs:  In the Soldier Mtns, it would take some bad luck to trigger a huge, 2-6 foot thick avalanche on weak layers that formed in January. But, the consequences would be devastating. You're most likely to trigger one of these beasts on very steep, NW-E facing, middle and upper elevation slopes. Slopes where the wind frequently blows have variable snowpack depths (deep and shallow) and a better chance of triggering these large avalanches. 

  • Loose Wet

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

    Natural wet avalanches are very likely to release where significant rain falls. In addition, today's warm, steamy weather will make wet avalanches possible in lower and middle elevation terrain that does not receive rain. The rain line line is expected to rise to near or above 7000' this afternoon. The wet loose slides are most likely on slopes steeper than about 35 degrees. Most slides will be relatively small, but some avalanches could gouge down into a damp snowpack, flank out as slabs, and become large enough to break trees. 

    During rain-on-dry-snow events, snow stability is unpredictable and can change rapidly. After hours of steady rainfall and no avalanches, a widespread avalanche cycle can occur as if a switch has been flipped. The safe move is to avoid playing on or under large or consequential avalanche paths where steady rain falls. 

    Roof avalanches: The warm temperatures and rain will make large roof avalanches likely this afternoon through Monday. Roof avalanches have killed people in Idaho and neighboring states, and several close calls have occurred locally in recent years. Click here for information and photos.   

Avalanche Discussion

The mountains near and east of Ketchum and Hailey are expected to pick up 1-4" of snowfall today, not enough to create significant new snow avalanche problems. We could see some rain or temperature driven wet loose avalanches this afternoon, but we expect few, if any, of these to be large enough to bury people. Near HWY75, the danger is MODERATE, and the Persistent Slab problem remains the primary avalanche concern at middle and upper elevations:

 Slabs that formed in early February rest above a variety of ugly, widespread, weak layers (facets, surface hoar, crusts, and combinations). Tuesday, a large persistent slab avalanche was triggered on a NW facing slope on Patterson Pk above Hailey.

Observers and professionals around the Wood River Valley continue to report frequent collapsing or whumpfing. These are clear signs that triggering one of these slides remains a real possibility. Persistent Slabs can release in surprising ways and break much wider than expected. You are most likely to trigger a dense, 2-4 foot thick avalanche where:

  • The snowpack is less than about 4 feet thick—this is the case on many slopes surrounding the Wood River Valley. Relatively shallower spots may exist where the wind frequently blows.
  • Any part of the slope you are on or connected to is steeper than about 35 degrees
  • The slope faces the northern 2/3 of the compass
  • A smaller wind slab or loose snow avalanche overloads the buried weak layers

You can view photos and details on recent Persistent Slab avalanches on Patterson Pk and Sun Mountain.

 

Regioni coperte