Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Monday, February 19th at 6:45 a.m. Today’s advisory is sponsored by Cooke City Super 8/Bearclaw Bob’s and Alpine Orthopedics. This advisory does not apply to operating ski areas.
The mountains near Bozeman and Big Sky got 2-4” of snow yesterday morning and 1” of snow overnight. Near West Yellowstone and Cooke City got 5-7”. Temperatures this morning are teens to single digits below zero F. Wind is south-southwest in Hyalite and Big Sky, and is easterly elsewhere at 5-15 mph and 25-35 mph in the Bridger Range. Today, temperatures will reach single digits above and below zero F, wind will be east-northerly at 5-15 mph, and light snow will dust the mountains with 1-2”.
Over the weekend, the mountains near Cooke City got 3 feet of snow equal to 3” of snow water equivalent (SWE). Strong westerly wind on Saturday drifted this snow into slabs at all elevations. Moderate east wind last night formed slabs near ridgelines on aspects that don’t often have drifts. Today, wind slabs 1-4’ deep are easy to trigger near ridgelines, and on rollovers and cross-loaded gullies at all elevations. Avoid large cornices and slopes below, and avoid round pillows or whales of snow on steep slopes.
Cooke City has received steady snowfall this winter and is buried with over 12 feet of snow. On non-wind loaded slopes, large avalanches of recent snow are possible. Last weekend, a snowmobiler triggered a slide 2-4 feet deep. He was fully buried and recovered quickly by his partners (photo). Similar slides are possible today. Careful snowpack and terrain evaluation are essential. Avalanche danger is CONSIDERABLE on wind loaded slopes and MODERATE on all other slopes.
Since Friday, the mountains near Bozeman and Big Sky got 1-2 feet of snow equal to 1.5-2” of snow water equivalent (SWE), and near West Yellowstone got over 2 feet of snow equal to 2-2.5” of SWE. Strong west wind on Saturday drifted snow into slabs near ridgelines and at all elevations. I found these wind slabs in the northern Bridger Range on Saturday (video). Yesterday, a skier in Hyalite saw a small natural avalanche (photo), and riders near Tepee Basin saw a natural avalanche on a heavily wind loaded slope (photo). Light to moderate east wind last night drifted snow into slabs near ridgelines and places not commonly loaded by wind.
Doug and I rode on Buck Ridge yesterday where we saw huge cornices (photo), zero avalanches or obvious sings of instability, and found a stable snowpack below 16” of fresh snow. Large cornices and fresh wind slabs are the main concern today. Avoid monstrous cornices, slopes below, and fresh drifts on steep slopes.
On non-wind loaded slopes, dry loose avalanches and slabs of recent snow are possible to trigger. These are more likely in areas that received more snow last night, like West Yellowstone. Avoid steep slopes if you see signs of instability like shooting cracks, collapsing, or fresh avalanches. Avalanche danger today is MODERATE.
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
BOZEMAN
Feb. 28th, Know Before You Go avalanche awareness, 7:00 p.m. @ Procrastinator Theater, MSU
March 2nd and 3rd, SheJumps Companion Rescue Clinic, Info and Register HERE
March 2nd, Avalanche Awareness, 7-8:00 p.m., MAP Brewing Bozeman Split Fest
March 7th, Avalanche Awareness, 6-7:30 p.m. @ REI
DILLON
Feb. 24th and 25th, Snowmobile intro to avalanches w/ field course. More info: https://msuextension.org/conference/.
COOKE CITY
Every Friday and Saturday, Current Conditions Update and Avalanche Rescue, Friday 6:30-7:30 p.m. at The Soda Butte Lodge in February. Saturday anytime between 10-2 @ Round Lake.
On Saturday 2/17, a skier was caught and killed in an avalanche in the backcountry near Jackson Hole Mountain Resort (Article). This is the eight avalanche fatality in the U.S. this season.