Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Sunday, March 18th at 7:00 a.m. Today’s advisory is sponsored by Mystery Ranch and Stronghold Fabrication. This advisory does not apply to operating ski areas.
Since yesterday morning the mountains near West Yellowstone got 2-3” of new snow, near Cooke City and Big Sky got 1”, and near Bozeman got zero to a trace. Yesterday, wind was out of the east-southeast at 15-25 mph, and this morning shifted southwest with gusts of 30-45 mph. Temperatures this morning are single digits to teens F. Today will be mostly cloudy with light snow showers, temperatures in the 20s F, and west-southwest wind at 15-25 mph. The mountains will get 1-2” by morning with 3-5” possible near Big Sky.
The new snow that fell Thursday created unstable slabs 8-12” thick that are possible to trigger today. On Friday, we observed natural and human triggered avalanches near Bridger (photo, photo) and in Beehive Basin (video). Yesterday, skiers near the Throne reported cracking 6-10” deep and saw recent natural avalanches, and skiers in Hyalite triggered an avalanche 8-10” deep and 200’ wide (video). The recent snow formed a thick slab on top of lower density snow above an ice crust, which is stabilizing slowly (snowpit).
Moderate wind over the last 24 hours drifted snow into thicker slabs. These fresh wind slabs are possible near ridgelines and along the base of cliffs, and found on a variety of aspects due to east to southwest wind directions. Be cautious of wind loaded slopes and slopes steeper than 35 degrees. Cracking of the snow surface on small rolls and test slopes is a clear sign to avoid steep terrain. Today, avalanches are possible to trigger and avalanche danger is MODERATE.
The mountains near Cooke City and West Yellowstone got less snow (4-6” since Thursday) and don’t have signs of instability like the northern part of the advisory area. The primary concern today is fresh drifts of snow formed by moderate to strong east and southerly wind. These wind slabs are possible to trigger near ridgelines, and located on many aspects or unusual locations due to the wide range of wind direction.
Cornices along ridgelines are massive throughout the advisory area. Keep a far distance from the edge along ridgelines and avoid slopes below. Cornices can break farther back than expected and can trigger larger slides (photo). Besides new snow instabilities and cornices, the snowpack is mostly stable and triggering a deeper avalanche is not likely (video, video).
Moderate to strong wind over the last 24 hours formed wind slabs that are possible to trigger today, and avalanche danger is MODERATE on wind loaded slopes and LOW otherwise.
If you get out and have any avalanche or snowpack observations to share, drop a line via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).
Upcoming Avalanche Education and Events
LIVINGSTON
March 20, Beer for a Cause Night at Katabatic Brewing, 4-8p.m. A dollar from every pint will be donated to The Friends of the Avalanche Center.
Alex and Eric wrote up a one-page accident report on the avalanche that caught a snowmobiler on Kirkwood Ridge in the southern Madison Range on March 7th that is worth looking at: accident report, video.