Tetons

Two substantial avalanches occurred yesterday. A snowmobiler was caught and fully buried in Horseshoe Bowl on Teton Pass. Luckily, companion rescue was successful. A very large slab also released naturally on the east face of Buck Mountain at an elevation of 11,500 feet. In steep, wind loaded avalanche prone terrain at the upper elevations, skiers and riders could trigger large, dense wind slabs. Daytime warming will increase the likelihood of triggering these slabs and also bring about the possibility of shallow wet loose slides. High temperatures are forecasted to be around 5 degrees warmer than yesterday, and Considerable hazard could develop in the afternoon if mostly sunny skies dominate. As yesterday’s slide on Buck Mountain illustrates, the avalanche hazard is heightened above 10,500 feet. Significant avalanche activity is unlikely below 8,500 feet. Get an early start, monitor warming conditions and solar input, and be willing to alter your travel plans if conditions warrant.

Flow aloft will slowly back to the west, and a Pacific weather system will bring another round of snowfall to the area from midnight through most of the day on Sunday. By Sunday evening, five to ten inches of new snow could fall in the Tetons with lighter accumulations in the other two forecast zones. Overnight lows in the mountains will be in the low 20s before rising into the upper 20s during the day. Nighttime temperatures in the valleys will drop to near freezing before climbing into the mid-40s in the afternoon, and a mix of rain and snow will be possible during the day. Southwesterly ridgetop winds will increase to 20 to 30 miles per hour.The general avalanche hazard is expected to be Moderate above 8,500 feet on Sunday. New snow and strong southwesterly ridgetop winds will create new pockets of wind slab in leeward terrain and add depth and volume to existing slabs on slopes not impacted by the sun on Friday. Skiers and riders could trigger these slabs in steep avalanche prone terrain. Newly developed slabs are likely to range in depth from 6 to 12 inches, and slabs that formed during the last week could range from two to three feet deep. Below 8,500 feet, backcountry travelers might be able to trigger similar slabs on very steep isolated terrain features and couloirs. Otherwise, avalanche activity will be unlikely down there. Monitor the development of the new slabs, and be willing to alter your travel plans if conditions warrant.