Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Saturday, February 21, at 7:30 a.m. Mystery Ranch in partnership with the Friends of the Avalanche Center sponsors today’s advisory. This advisory does not apply to operating ski areas.
Since yesterday morning another 5 inches fell in the Bridger Range, over a foot in the northern Gallatin Range, and 4-8 inches in the northern Madison Range. Further south, Cooke City and the southern Madison Range got 2-4 inches while the mountains near West Yellowstone got a trace at best. Temperatures this morning were in the low to mid teens F with north winds blowing 5 mph gusting 15 mph. In the Bridger Range, winds were blowing from the E at 15-20 mph.
As cold air descends over the area today, temperatures will drop a few degrees, and snowfall will end around midday. A few more inches may accumulate mainly near Bozeman and Big Sky, and winds may increase some this afternoon.
Bridger Range Northern Madison Range
Northern Gallatin Range
In the last 48 hours, the Bridger Range and northern Gallatin Range received 1.0 and 1.3 inches of snow water equivalent respectively totaling over a foot of snow, and the mountains near Big Sky received 0.5 inches of snow water equivalent. Some places like Hyalite in the northern Gallatin Range could easily have 2 feet of new snow today.
Yesterday observers in the Bridger Range and northern Gallatin Range reported right side up snow (light snow on top of warmer denser snow). They also reported a relatively good bond between the new and old snow; however, skiers in Hyalite Canyon observed one small avalanche, and skiers just north of Bridger Bowl triggered two soft slab avalanches about 1 foot deep on steep rollovers (photo). Ski patrols at Big Sky and Bridger easily ski cut shallow soft slab avalanches involving the new snow.
The new snow needs another day or so to bond to itself and to the old snow underneath. With a few avalanches yesterday and more snow overnight, human triggered avalanches will be likely. Additionally, north and east winds will easily transport today’s low density snow and form wind slabs that will be easy to trigger. Today the avalanche danger is rated CONSIDERABLE on any slope steeper than 35 degrees or any wind loaded slope. Less steep slopes without wind-blown snow will have a MODERATE danger.
Southern Madison Range Southern Gallatin Range
Lionhead Area near West Yellowstone Cooke City
The mountains near Cooke City and the southern Madison Range received 3-6 inches of snow (0.3 inches of snow water equivalent) in the last 48 hours while West Yellowstone was basically dry. Without much new snow there are few avalanche concerns. Some slopes mainly near West Yellowstone, Teepee Basin, and the Taylor Fork area may have a layer of surface hoar buried 1-2 feet deep, but this layer is not everywhere and has only produced two small avalanches that we know of. Shallow wind slabs in isolated areas will be the main concern. Today the avalanche danger is MODERATE on wind loaded slopes steeper than 35 degrees while all other terrain will have a LOW danger.
Eric 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.
AVALANCHE EDUCATION and EVENTS
Take a look at our Education Calendar for all classes being offered.
TONIGHT, 1-hour Avalanche Awareness, West Yellowstone, Holiday Inn, 7 p.m., Saturday, February 21.
Snow Science and the Human Factor, Big Sky, location TBD, 6-8:00 p.m., Tuesday, February 24. The free event will feature a talk by Powder editor and MSU graduate John Stifter, multimedia presentations on the human factor in avalanche risk, a panel of experts from MSU’s Snow & Avalanche Lab and Gallatin National Forest Avalanche Center, as well as a Q & A session.