Good morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Sunday, December 9 at 7:30 a.m. Today’s advisory is sponsored by On Site Management and Alpine Orthopedics in partnership with the Friends of the Avalanche Center. Bridger Bowl is now open and uphill travel within its boundaries is no longer permitted.
Over the past 24 hours a moist northwest flow delivered 18” of cold smoke powder to the Bridger Range. The northern Gallatin and northern Madison Ranges along with the mountains around Cooke City picked up 8-10 inches. The mountains around West Yellowstone received 2-3 inches. Currently, temperatures are in the single digits above or below zero F and winds are blowing 5-10 mph from the WNW. Today, high temperatures will be 5-10 degrees above zero F and winds will gradually increase out of the WNW. Skies will be mostly clear this morning, but will become mostly cloudy by this afternoon. Tomorrow looks to be a warmer with snow likely.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
It finally looks and feels like winter (huge smile)! Yesterday, I received numerous reports from Big Sky to Bridger Bowl that skiers actually choked on snow. It feels like eternity since I’ve been able to write that. This is a fine replacement over the pineapple express that impacted our area over the past few weeks.
Today, the primary avalanche concern will be wind loaded slopes. Fresh wind drifts on the leeward side of ridgelines and cross-loaded terrain features will be sensitive to the weight of a skier or rider. Yesterday, the Big Sky and Moonlight Basin Ski Patrol triggered numerous wind slabs during control work. Ice Climbers in Hyalite also triggered small wind slabs on Friday. Ice climbers need to be especially aware of wind loaded terrain, since small avalanches can have huge consequences.
A secondary problem is buried facets. Yesterday, the Big Sky Ski Patrol triggered 2 avalanches during control work that failed on facets near the ground. These slopes were heavily wind loaded and represented a backcountry snowpack. A similar event was observed by skiers near Quake Lake in the southern Madison Range on Thursday (photo). I also found a layer of small grained facets on Mt Blackmore yesterday. This layer propagated during stability tests, which kept us skiing low angle terrain (snowpit).
Buried facets have also been found in the Bridger Range (snowpit). This layer is being tested for the first time in weeks. I don’t expect to see avalanches failing at the ground, but it is possible. Steep, rocky terrain, specifically where the snowpack is shallow will be likely areas to produce deeper avalanches.
Last but not least. Mark found a buried layer of surface hoar in the Taylor Fork area of the Southern Madison Range last Wednesday (video). We have limited data on the distribution of this weak layer but suspect it may exist near Cabin Creek, Teepee Basin and Lionhead. This layer is scary because it exists in isolated pockets on slopes sheltered from the wind. It’s worth digging a snowpit to look for this layer before riding on steep slopes.
For today, the avalanche danger is rated CONSIDERABLE on all wind loaded terrain. On slopes without a wind load, the avalanche danger is rated MODERATE.
I will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations drop us a line at mtavalanche@gmail.com or call us at 587-6984.
Snowmobiler Introduction to Avalanches with Field Course in Billings at Hi-Tech Motor Sports on December 12 and 13, 6-9 p.m. and the field course on January 20 in Cooke City. Sign up for this class HERE
Snowmobiler Introduction to Avalanches with Field Course in West Yellowstone on December 20 and 21. Sign up for this class HERE.
FREE 1 hour lectures:
December 12, REI in Bozeman, 6:30 p.m.