Good Morning. This is Doug Chabot with the Gallatin National Forest Avalanche Center’s early season avalanche information issued on Wednesday, November 30 at 7:00 a.m. Today’s bulletin is sponsored by Alpine Orthopedics and Buck Products. We will update this information on Friday morning.
Early yesterday morning, lingering snow showers dropped 2” in the Bridger Range and a trace to 1” elsewhere. At 5 a.m. under clear skies, temperatures are colder in the north (single digits) than the south (teens). Winds are SW-NW at 10-15 mph. Later this afternoon a NW flow will bring clouds and scattered snow showers lasting through Thursday. By Friday morning 3-5” are expected in the mountains.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
The mountains have a thin snowpack. The average depth ranges from 17-21” in the north to 20” at Carrot Basin, 14” around West Yellowstone and 26-30” outside Cooke City. Deeper snow can be found on wind-loaded slopes while thinner areas are located on south facing and/or wind-scoured areas. Even with varying depths, our stability concerns are similar.
- Every mountain range has at least one layer of weak, faceted snow.
- In areas where these facets are capped by a denser slab (wind-loaded or new snow) skiers are reporting collapsing and cracking. This was seen by the Bridger Bowl Ski Patrol yesterday, outside Cooke City over the weekend and in Beehive Basin on Friday.
- The snowpack is susceptible to faceting because it is thin, the days are short and cold, and the nights are long and even colder. The temperature difference between the very cold snow surface and the relatively warm ground creates weak, angular, sugary snow termed facets.
Yesterday, Eric and I toured into Lionhead on a 12-14” snowpack which will inevitably become weak as the facets grow, and unstable with future snowfall (video, photo). As Eric said, “It’s going to get worse before it gets better.”
Alex’s video from his weekend visit to Cooke City and my video of the northern Bridger Range from Sunday, concur with the overall avalanche concern: on deeper, wind-loaded slopes, especially if they harbor a weak layer of faceted snow, avalanches are possible. The recent reports of cracking and collapsing are important to remember as they signal unstable conditions.
Eric will update this bulletin Friday morning. We will begin issuing daily advisories and danger ratings when we get more snow.
We rely on your field observations. Send us an email with simple weather and snowpack information along the lines of what you might share with your friends: How much new snow? Was the skiing/riding any good? Did you see any avalanches or signs of instability? Was snow blowing at the ridgelines? If you have snowpit or test data we'll take that too, but this core info is super helpful! Email us at mtavalanche@gmail.com or leave a message at 406-587-6984.
BOZEMAN
TONIGHT! 30 Nov. and 1 Dec., Introduction to Avalanches with Field Course, 7-9:30 p.m. at MSU Sub Ballroom B. Sign up HERE.
6 December, Avalanche Awareness, 6-7:30 p.m. at MSU with Backcountry Squatters Ski Club, SUB Procrastinator Theater.
7 December, Avalanche Awareness, 6-7:30 p.m. at REI.
15 December, Avalanche Awareness and Beacon Practice, 6-8 p.m. at Beall Park.
BUTTE
TOMORROW! 1 December, Snowmobiling In and Identifying Avalanche Terrain, 6-7 p.m. at Redline Sports
HELENA
8 December, Avalanche Awareness, 6-7:30 p.m. at The Basecamp.
WEST YELLOWSTONE
15 and 16 December, Snowmobile Introduction to Avalanches w/ Field Day, West Yellowstone Holiday Inn Conference Hotel. More info and sign up HERE.
COOKE CITY
Every Friday and Saturday, Weekly rescue training and snowpack update, Cooke City Chamber of Commerce on Friday 6-7:30 p.m. and field location TBA for Saturday.
BILLINGS
15 December, Snowmobiling In and Identifying Avalanche Terrain, 6-8 p.m., location TBA