Good Morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Sunday, March 16 at 7:30 a.m. Gallatin County Search and Rescue in partnership with the Friends of the Avalanche Center sponsors today’s advisory. This advisory does not apply to operating ski areas.
The full moon was bright all night and no new snow has fallen. This morning, mountain temperatures are in the 20s F and winds are blowing 10-20 mph out of the west with gusts in the 30s. Today, skies will start out mostly clear but will cloud up by this afternoon. Temperatures will warm into the mid-30s to low 40s F and winds will gradually increase out of the west blowing 25-35 mph. A fast moving storm will impact southwest Montana starting Monday morning. 3-6 inches of new snow is likely in the mountains by Monday night.
Cooke City
Riding on big, steep slopes around Cooke City is a very dangerous proposition right now. Over the past few days many large human triggered avalanches have occurred.
On Wednesday March 11th, a snowmobiler was killed in an avalanche on the northeast face of Crown Butte (accident video, snowpack video, photos). Yesterday, a snowmobiler suffered two broken legs when they were caught in a slide on the south face of Mt. Abundance (photo). Another snowmobiler had a very close call yesterday below Chimney Rock near Daisy Pass (photo). This slide occurred on a similar slope to the fatal Crown Butte slide (photo).
The scariest part of all of this activity is that the avalanches are releasing on facets near the ground - making for big slides with even bigger consequences. The best way to deal with these conditions is avoidance - stay off steep slopes and out from avalanche runout zones. Tracks on a slope do not mean it is stable.
Today, dangerous avalanche conditions exist on slopes steeper than 35 degrees which have a CONSIDERABLE avalanche danger. Less steep slopes have a MODERATE avalanche danger.
Bridger Range Gallatin Range Madison Range
Lionhead area near West Yellowstone
Warm and calm weather over the past 24 hours has helped stabilize new snow instabilities that developed during Friday night's storm. It remains possible for backcountry travelers to trigger isolated wind slabs near the ridge tops. Keep this in mind if you're traveling in upper elevation terrain.
A more complex problem is triggering avalanches that break on deeper layers in the snowpack (photo). Facets buried mid-pack and near the ground produced large natural avalanches during the potent storm that dropped heavy snow last week (photos). Since the snowpack has time to adjust, avalanches are becoming harder to trigger. However, if a skier or rider does trigger a slide on a deeply buried weak layer, it will likely result in a large and dangerous avalanche (video). These types of avalanches will be easiest to trigger in steep, rocky terrain where the snowpack is thinner.
Now is no time to let your guard down. Make sure everyone in the group is carrying rescue gear, always watch your partner from a safe location and never expose more than one person on a slope.
Today, human triggered avalanches are possible and the avalanche danger is rated MODERATE.
CORNICES
Three days ago, a person walking along the ridge north of Bridger Bowl outside the ski area received minor injuries (luckily) when a cornice broke underneath him and he tumbled about 1200 feet down slope. The falling cornice caused slabs to fracture and carried this person further than they would have fallen otherwise. Cornices are large now and creep during warm weather. They are unpredictable, deadly, and often break further back than you would expect. Give these monsters a wide berth.
This person commented that he was at least 10 feet from the edge. This strategy doesn’t work when it’s a 20 foot cornice. Think about where the cornice starts not where it ends.
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.