Bollettino valanghe

Salt River and Wyoming Ranges

Bridger-Teton Avalanche Center
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Pericolo valanghe

Tue
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
Senza grado
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In sintesi

It is possible for backcountry travelers to trigger large avalanches failing on weak snow near the ground. Steep, shaded terrain at the middle and upper elevations are most likely to produce a destructive avalanche. Carefully evaluate the snowpack structure before committing to a slope.

Problemi valanghivi

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    Slabs of cohesive snow 2-3 feet thick overlay weak, faceted snow that formed during a dry period in November. Hard slab avalanches failing on this weak interface are most likely on west, north, and east aspects above 8,500’. Although a week of dry weather has made these slabs less sensitive to humans, the possibility of triggering a dangerous avalanche still exists. Predicting these avalanches is becoming more difficult as a slide may not release until several riders have ridden the slope. Previous tracks do not indicate stability with this problem. Collapsing a buried weak layer in a shallow portion of the snowpack, typically near rocks and sparse trees, is the best way to trigger one of these avalanches. If triggered, the resulting avalanche may be large, destructive, and pull out into lower angle terrain than expected. Maintain a wide margin around steep, rocky slopes that face away from the sun to avoid triggering a dangerous hard slab avalanche.

    Persistant slab avalanche. 10,500' SE aspect likely occurred on 12/10 after loading event when winds increased. 

    Steep, rocky, and wind loaded terrain like this is where you are most likely to encounter this problem.

    Photo: Alex Drinkard

Avalanche Discussion

The snowpack in the Greys River Forecast area varies significantly from relatively deep in the Salt River Range to much thinner in the Wyoming Range. As a result, slopes where the persistent slab problem can be found will differ slightly from one range to another. What remains consistent is the fact that avalanches are possible anywhere weak, sugary snow sits beneath a stiff slab. This is most likely the case on slopes with a northerly aspect. However, any slope with old snow at the base of the snowpack should be approached with caution. Digging into the snowpack is the only way to know for sure if this problem exists. Trenching your snowmobile or probing with a pole to feel for hardness changes (hard snow over soft snow) are easy ways to identify this layer. Remember that a slope 50 yards away from the one you just dug on will likely hold a different snowpack.

Triggering a large avalanche in steep terrain is still possible, especially if you happen to find the right shallow spot. Snow depths are highly variable and many slopes are littered with potential “trigger points''. Right now, committing to a steep slope with poor structure is committing to the uncertainty that you may trigger a destructive avalanche. Although the mountains have become quieter in recent days, it is important to remain vigilant and give steep, consequential slopes the respect they deserve. Time will continue to stabilize the snowpack, but for now choosing to ride lower angle terrain can help you avoid triggering a dangerous avalanche.

Regioni coperte