Avalanche forecast

Tetons

Bridger-Teton Avalanche Center
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Avalanche danger

Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Dangerous avalanche conditions exist above 9,000 feet. Yesterday afternoon, a snowboarder remotely triggered a 12 inch deep slab on a south facing aspect around 8,000 feet in Grand Teton National Park. Similar small to large wind slabs will be likely on steep, wind loaded slopes at the mid and upper elevations. Much higher consequences are associated with persistent weak layers buried deeply in the snowpack. On a variety of aspects above 7,500 feet, backcountry travelers could trigger large to very large, deadly slab avalanches failing on these weak layers. Avalanche activity below 7,500 feet is expected to be limited to steep, isolated terrain features. Monitor the timing of the incoming storm system, and have a plan to back off if it arrives earlier than expected.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2

    Since Saturday morning, 12 to 18 inches of new snow has fallen in the higher elevations. Light density snow and light to moderate winds were followed by denser snow and southwesterly to westerly ridgetop winds that increased to 25 to 35 miles per hour for most of the day on Sunday. Upside-down conditions and substantial leeward loading resulted, and wind slabs gained depth and volume. These slabs reside above a variety of snow surfaces which include surface hoar, near surface facets, wind pack and sun crusts. Above 7,500 feet, skiers and riders could easily trigger these slabs on steep, wind loaded slopes.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Persistent weak layers of faceted snow associated with the December 11th interface vary significantly across the landscape. Since Saturday morning, around an inch and a half of snow water equivalent has been added to these layers. Above 7,500 feet, backcountry travelers have the potential of triggering slab avalanches failing on these layers with depths ranging from two to five feet. The release of a wind slab could also initiate one of these deadly slides. Previous tracks are not an indication of stability, and conservative terrain choices are the best tool to manage this hazard. With the exception of steep, isolated terrain features, the snowpack is mostly stable below 7,500 feet.

Avalanche Discussion

A Winter Weather Advisory has been issued by the National Weather Service. It is effective until 3pm Tuesday. Snow is expected with the heaviest snowfall to occur between 7 pm this evening and 3 am Tuesday. Approximately 10 inches of snow and nearly an inch of moisture is expected overnight. Winds are to increase to averages of 25 to 40 miles per hour and become westerly Tuesday morning. Snow is to diminish Tuesday morning as winds lessen and become northwesterly. Mountain temperatures are to rise from the low teens to the twenties. The general avalanche danger in the Teton and Southwest trails areas could increase to HIGH if both significant snowfall and strong winds occur. In the Togwotee pass area, the danger is likely to increase to Considerable. Wind slabs involving the new storm snow and possibly recent snow could be human triggered with depths to two feet in steep freshly loaded terrain. The primary focus and reason for conservative decision making involves buried persistent weak layers of faceted snow. Failure of these layers could result in very large avalanches at higher elevations or widespread smaller avalanches at lower elevations. Under these conditions, collapses in the snowpack could remotely trigger slides. Be sure to avoid being under suspect slopes.

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