Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Thursday, January 31 at 7:30 a.m. Montana Ale Works, 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 15 inches of snow fell in Hyalite Canyon, 10-12 inches near Bridger Bowl, 8-9 inches near Big Sky and Cooke City, and 2-6 inches near West Yellowstone. Westerly winds have been averaging 20 mph and gusting to 40-50 mph. This morning temperatures were in the high teens F and should rise to the low 20s F today. Winds will remain westerly and ease slightly, blowing 15 mph with gusts of 30-35 mph. Snowfall will continue today. By tomorrow morning most areas will get an additional 3-6 inches. The mountains near West Yellowstone will receive 2-3 inches.
Bridger Range Northern Gallatin Range
The message for today is simple. Heavy snowfall + strong winds will create both natural and human triggered avalanches. There are three avalanche problems which are interesting to discuss but irrelevant to the travel advice today. Avoid avalanche terrain.
- Strong winds have created fresh drifts and wind slabs. Doug and Eric intentionally triggered a small avalanche yesterday on a little test slope that had fresh wind drift. More will occur today.
- Yesterday’s snow is much denser (12% at Bridger) than Tuesday’s snow (3%) creating upside down conditions. This set up caused Doug and Eric to back off a 32 degree slope yesterday (video).
- Some slopes, especially in the northern Gallatin Range, have a thin, weak snowpack. Skiers on Mt Ellis found a very weak snowpack, 2-2.5 feet deep. Similar slopes exist in Hyalite Canyon. With 1.2-1.6 inches of snow water equivalent falling in the last 24 hours, these slopes will not be able to support this much weight and may produce avalanches breaking deeper in the snowpack.
Today, the avalanche danger is rated HIGH on wind loaded slopes and CONSIDERABLE on all others.
Madison Range Southern Gallatin Range
Lionhead area near West Yellowstone
Areas further south received less snow but plenty of wind making fresh wind slabs the primary avalanche problem. Another problem is several layers (video, photo) of weak facets (and some surface hoar - photo) that formed on the snow surface during dry weather in both early and mid-January. They are now buried 1-2 feet deep. These layers are widespread closer to West Yellowstone. They also exist near Big Sky on many slopes but seem to be more sensitive on south aspects. New snow, wind, and buried weak layers mean dangerous avalanche conditions exist today and the avalanche danger is rated CONSIDERABLE.
Cooke City
The mountains near Cooke City have a single avalanche problem – fresh wind slabs. This area mostly lacks buried weak layers of facets. For today the avalanche danger is CONSIDERABLE on wind loaded slopes and MODERATE on all others.
I 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.
February 16: 11th Annual King and Queen of the Ridge
The 11th Annual King and Queen of the ridge Hike/Ski-a-thon fundraiser is Saturday, February 16. The event supports avalanche education. Enter as an individual or a team. Collect pledges for the number of hikes you can do in five hours. Kids and families are encouraged to hike too! Prizes will be awarded to the most hikes (1st, 2nd, and 3rd); most money raised, most laps for a team, most money raised for a team. More Information / Registration Form
TONIGHT In Helena at 6:30 p.m., the Friends are giving a free 1-hour Avalanche Awareness lecture at Exploration Works (995 Carousel Way).
In Bozeman, on Wednesday, February 6, REI is hosting a 1-hour Avalanche Awareness lecture for Women. Space is limited and registration is required: http://www.rei.com/event/47916/session/64605
The Friends are teaching a free Companion Rescue Course in Big Sky, at Grizzly Outfitters, on Friday, February 8 from 6-8 p.m., followed by a field session the next day from 10 a.m. to 2 p.m. Space is limited and pre-registration is required: https://ticketriver.com/event/5830-companion-rescue-clinic-for-skiers-&-boarders