Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Center with early season avalanche information issued on Thursday, November 17 at 8 a.m. Today’s bulletin is sponsored by Yellowstone Arctic Yamaha and Yamaha Motor Corp. This information will be updated as conditions change.
Winter has made a welcome appearance. Snowfall totals over the past 48 hours are 6” near Bozeman and Big Sky, 14” near Cooke City, and 16” near West Yellowstone. Wind overnight was out of the northwest at 10-15 mph with gusts near 20 mph. Temperatures this morning are 10-20 F and will reach the mid-20s F today. Wind will be 5-15 mph out of the north to northeast today, and 1-2 more inches of snow will fall before the storm ends this afternoon.
Storm totals equal almost 1.5” of snow water equivalent (SWE) in the mountains near West Yellowstone and Cooke City, and around 0.5” of SWE elsewhere. Prior to this storm there was a patchwork of snow cover in the mountains. High elevation (>9,000’), shady slopes near Cooke City and south of Bozeman had around 2 feet of consolidated snow (photo) while low elevation slopes and slopes exposed to sun showed only dirt, rocks, and logs. Instabilities commonly associated with new snow and moderate wind are expected, and slides are most likely where slabs formed over an existing snow surface.
The best skiing and riding will be where the snow is deepest, which will also be where avalanches are most likely. Deeper pockets of wind-drifted snow will be found near ridgelines and on leeward slopes. If a slope has enough snow to ride it has enough snow to avalanche. Even small slides can be dangerous or fatal. Be cautious when crossing small slopes above cliffs, confined gullies, or road-cuts where a small avalanche has high consequences. A thin snowpack increases the potential for injury from rocks or logs if caught in a small slide.
Hunters and skiers are subject to the same avalanche hazard this time of year. Hunters often travel alone and don’t carry rescue gear, so they should avoid avalanche terrain. An avalanche that caught two hunters last November shows the potential for a bad situation, but with a fortunate outcome as only non-critical injuries were sustained.
Travel and prepare for avalanches like you would in the middle of winter. Choose terrain cautiously and travel one at a time in avalanche terrain, whether descending or climbing. Put fresh batteries in your beacon, check your shovel and probe for damage, and practice using all your gear (video).
We will update this information as conditions change. In the meantime, we need your observations, so if you get out please drop us a line at mtavalanche@gmail.com or call 406-587-6984.
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.
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
25 Nov. and 26 Nov.; 2 Dec. and 3 Dec.; 9 Dec. and 10 Dec., Weekly rescue training and snowpack update, Cooke City Chamber of Commerce on Friday and field location TBA on Saturday.