Bollettino valanghe

Tetons

Bridger-Teton Avalanche Center
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Pericolo valanghe

Alta quota
3 · Marcato
Limite del bosco
1 · Debole
Sotto il limite
Senza grado
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In sintesi

Backcountry travelers reported several slides yesterday that have occurred since Thanksgiving. These slides all appear to have failed on faceted snow above the October rain crust and had crown depths ranging from 6 to 18 inches. Today, backcountry travelers are likely to trigger similar slides in steep, wind-loaded terrain that held snow from October. The likelihood of triggering these slides will increase during the day as new snow and sustained southwesterly to westerly ridgetop winds combine to create unstable conditions. In isolated areas, these conditions will extend into mid elevation terrain on northerly aspects where the October rain crust is present. At the lower elevations, the snowpack lacks sufficient depth and structure for avalanche activity.

Problemi valanghivi

  • Persistent Slabs

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

    The primary layer of concern is faceted snow resting on the hard October rain crust. This persistent weak layer exists on westerly through northerly to easterly aspects above 9,000 feet. On mostly shaded slopes, this crust can dip below 9,000 feet. Southwesterly ridgetop winds have ranged from 15 to 25 miles per hour over the past 48 hours, which has transported snow and stiffened up surface slabs. Today’s snowfall and wind will increase the sensitivity of these slabs to human triggers and natural activity will be possible. These slabs could range in depth from one to two feet and have the potential to bury or serious injury skiers and riders.

Avalanche Discussion

Atmospheric instability is expected to produce convective snow showers over the mountains tonight. The next upper level disturbance will move into the region during the day. Tonight's snow shower activity is expected to favor the west slope of the Teton Range and the higher elevations where several inches of new snow accumulation or more is likely. Tomorrow’s disturbance should bring another 1 to 5 inches to the region. Temperatures will remain in the teens at the higher elevations, in the 20s at the mid elevations and should rise to near freezing in the valleys during the day. Winds along the high ridge crests will be westerly at 20 to 25 with gusts to 40 miles per hour.The general avalanche hazard is expected to be CONSIDERABLE at the upper elevations in the Teton area and MODERATE at the upper elevations of the Continental Divide/Togwotee Pass and Southwest Trails/Grey’s River areas. The hazard is expected to be LOW at the mid and lower elevations. Natural and human triggered avalanches are possible at the upper elevations and will be large enough to cause serious injury or death. Shooting cracks and whooping sounds associated with a collapse of a weak layer are signs of instability. Potential exists for dangerous slab avalanches to be remotely triggered from runout zones. A conservative approach to terrain selection is essential in steep terrain where a weak layer of faceted snow peersist on the October rain crust.

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