Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, December 11 at 7:30 a.m. Today’s advisory is sponsored by Javaman and Northern Lights Trading Company. This advisory does not apply to operating ski areas.
Snow fell yesterday and again last night. Since the beginning of the storm at 4 a.m. yesterday, seven to nine inches fell in the northern mountains (around Bozeman and Big Sky) with two to four inches in the southern ranges. Wind speeds have picked up out of the northwest and are blowing 20-30 mph. These speeds will increase slightly this morning and switch to the southwest later today. Under cloudy skies intermittent snowfall will measure one to two inches as temperatures climb from the teens to low 20s.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
Today’s avalanche story consists of two characters: new snow and wind. Like two hooligans they’ll create havoc. In the northern mountains it has snowed 11 of the last 13 days dropping two to three feet of dense snow (3-4” of SWE). In the southern areas three to four feet of snow has fallen in the last 12 days (5-6.5” of SWE). In the past 48 hours strong west to northwest winds are building thick drifts near the ridgetops which will likely be triggered today.
Weaker, sugary, facets are underlying all this snow on some slopes, but not all. The tricky part is finding out which is which. On Sunday, immediately south of Bridger Bowl’s boundary on the Football Field of Saddle Peak, Eric and I found facets. We dug into the weakest snow we’ve seen, which happens to be on the most heavily skied piece of real estate on the forest (video, photo). Facets one foot off the ground were popping clean in our stability tests (ECTP11 and 13, Q1). Recent wind-loading makes these slopes suspect. Over the weekend, in Beehive Basin a skier experienced collapsing and cracking which mirrored the instabilities two other parties found in the southern Madison Range (photo). Near Cooke City on Mt Republic a natural avalanche on Sunday was likely triggered by all the new snowfall (photo).
Cracking, collapsing and recent avalanches are signs of dangerous conditions; stick to slopes less than 30 degrees if you encounter these red flags. Without these signs I recommend digging to see if the slope you want to play on has buried facets. There are many slopes which will be safe, but they will not be obvious. For today, the avalanche danger throughout southwest Montana is CONSIDERABLE on all wind-loaded slopes and MODERATE on all others.
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:
Wednesday, December 12, REI in Bozeman, 6:30 p.m.