For more than a week, daily snowfall accompanied by strong winds has loaded slopes and formed wind slabs over a variety of surfaces. Above 9,000 feet, it is possible for backcountry travelers to trigger slab avalanches up to 3 feet in depth on avalanche-prone slopes. These slabs have been formed by the week’s weather events and could fail on a variety of layers from old buried surfaces to density breaks within the more recent snow. Backcountry travelers should use careful assessment when traveling through steep wind loaded terrain. At the mid-elevations avalanches will be possible to trigger on steep isolated wind-loaded features and avalanches are unlikely in the low elevations. We are sad to say that an initial report has come in about an avalanche yesterday in the Big Hole Mountains, which resulted in two fatalities. Our deepest condolences go out to the family and friends of those involved. More information will be provided as it becomes available.
Yesterday, strong southwest to northwesterly winds continued to build wind slabs at the upper elevations. These slabs will be most sensitive in steep upper elevation terrain and have the potential to step down to more deeply buried weak layers within the snowpack and be up to 3 feet in depth. Evaluate terrain and signs of wind loading carefully when traveling the higher elevations today.
The area is expected to remain dry with partly cloudy skies. Temperatures will drop into the single digits overnight and then warm into the twenties in the mountains and thirties in the valleys. Westerly ridgetop winds will be 15 to 25 miles per hour with gusts into the thirties. The avalanche danger will be Moderate above 8,000 feet. Where in steep, avalanche-prone terrain, it will be possible for skiers and riders to trigger avalanches up to three feet in depth. The variability of the buried weak layers and areas of loaded snow, make it important to check a slope's stability before crossing into steep terrain. As winds continue to transport snow at the upper elevations, small shallow wind slabs could be found along the high ridges. Below 8,000 feet, avalanches are unlikely.
