Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Sunday, December 4th at 6:45 a.m. Today’s advisory is sponsored by Excel Physical Therapy and Edward Jones. This advisory does not apply to operating ski areas.
Since yesterday morning the mountains near Cooke City received 5 inches of snow, 2-3 inches fell near Big Sky and West Yellowstone, and no snow fell in the mountains around Bozeman. Winds have been out of the west-southwest at 20 mph with gusts up to 45 mph. Temperatures this morning are in the teens F and will reach the high 20s F today. Expect strong wind today with speeds greater than 30 mph out of the southwest. By tomorrow morning the mountains will receive 6 to 10 inches of new snow near Bozeman and Big Sky, and up to a foot of new snow is expected in the southern mountains.
Bridger Range Northern Gallatin Range
Northern Madison Range
Natural and human triggered avalanches were observed yesterday in the mountains near Bozeman. New snow on Thursday was transported by wind Friday night to add more weight to a weak snowpack. Eric traveled north of Bridger Bowl yesterday and found unstable results in stability tests and saw avalanches, a sure sign of an unstable snowpack (video). Some slopes showed more stable snow, so take time to assess each slope before venturing into steeper terrain. Meanwhile in Hyalite, Doug retreated from an ice climb after he observed cracking in deep drifts of snow and triggered a small avalanche (video, photo, photo). Even small slides can be deadly for climbers in steep gullies or skiers in steeper, exposed terrain.
A weak, early season snowpack exists near Bozeman and Big Sky (photo). Strong wind today will continue to drift snow and stress this weak snowpack. Avalanche danger today is rated CONSIDERABLE.
Cooke City
The mountains near Cooke City have harbored snow longer than most of our advisory area, and weak layers have formed on many slopes. This area did not receive much snow during Thursday’s storm, but skiers have observed cracking, collapsing, and natural avalanche activity over the past couple weeks. New snow and wind today will form slabs and create unstable conditions (video). Avalanche danger today is rated MODERATE, and could rise to CONSIDERABLE if snowfall amounts increase early.
Southern Madison Range Southern Gallatin Range
Lionhead area near West Yellowstone
The mountains south of Big Sky and near West Yellowstone have not been favored for snow over the past week. However, the overall integrity of the snowpack is weak (video, photo) and more snow today and tonight will create unstable conditions. Avalanches will be possible today where wind has loaded slopes with new snow, and avalanches will become more likely as snowfall continues today. Avoid riding on or beneath steep terrain if you observe blowing snow or intense snowfall. Today, the avalanche danger is MODERATE.
I will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations please drop us a line at mtavalanche@gmail.com or leave a message at 406-587-6984.