During the past 30 hours the upper elevations of the Teton Range have received 10 to 12 inches of new snow with nearly an inch of moisture. This new snow has accumulated on very light density snow. In addition buried sun crust exist on southerly aspects and weak faceted snow exist at the base of the snowpack on northerly aspects. Temperatures have increased nearly 20 degrees during the past 48 hours and will continue to rise. The combination of new snow, warming temperatures and strong winds have created areas of unstable snow. The hazard is expected to continue to increase as the day progresses.
At the upper elevations surface slabs up to two feet in depth could be human triggered on a variety of aspects in steep avalanche prone terrain. On northerly aspects these slabs have the potential to steep down to depths of three feet. At the mid elevations isolated pockets of slab up to one foot in depth could be human triggered in steep, wind loaded avalanche starting zones.
A Pacific storm system that is moving across Washington State is expected to rapidly move east across Montana and into the Dakotas on Friday. An associated cold front will move across our area in the morning. Snow and areas of blowing snow are likely overnight and through the morning. Diminishing snowfall with continued areas of blowing snow are expected in the afternoon. The snow level will descend from 7,000 to 5,000 feet after the passage of the front. This system will favor Yellowstone National Park and the northern portions of our forecast areas which could receive four to 10 inches of additional snow. Winds will veer from the west-southwest to the west at 20 to 30 with gusts to near 50 miles per hour on the higher summits.Human triggered slab avalanches one to three in depth are possible on steep, wind loaded slopes at the upper elevations. Avalanches are unlikely at the lower elevations. The general avalanche hazard is expected to be MODERATE at the upper elevations and LOW at the mid and lower elevations on Friday. A higher hazard may occur in areas with prolonged periods of intense wind drifting.
