Good Morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Friday, December 3, at 7:30 a.m. Montana Ale Works, in cooperation with the Friends of the Avalanche Center, sponsor today’s advisory. This advisory does not apply to operating ski areas.
By 6 a.m this morning, the mountains near Cooke City had received 17 inches of snow, the Bridger Range and mountains near West Yellowstone received 7-10 inches, and the Madison and Gallatin Ranges received 4-5 inches. Temperatures were in the low 20s F with winds blowing 10-30 mph mostly from the west. Snowfall will continue this morning with another 2-3 inches. As cold air descends from the north, temperatures will drop into the teens F by this afternoon with the Bridger Range being the first to receive this cold air. Winds will decrease somewhat and blow 10-20 mph slowly shifting from the W to NW.
The mountains around Cooke City and the Washburn Range:
Almost 1.5 feet of heavy snow has fallen in the mountains north of Cooke City. This abundant snowfall brought strong winds which were ripping 20-50 mph from the WSW during the storm but decreased this morning to 10-20 mph shifting to the NW. These winds formed many fresh wind slabs that will produce avalanches. We have very limited data from this area, but skiers and riders have reported a generally strong snowpack, and avalanche activity will mostly occur within the new snow and new wind slabs. However, this heavy load of new snow has significantly stressed deeper layers in the snowpack, and some avalanches breaking on these layers are definitely possible. For today both natural and human triggered avalanches are likely on wind loaded slopes where the avalanche danger is rated HIGH. All other slopes have a CONSIDERABLE avalanche danger.
The Bridger, Gallatin and Madison Ranges and the Lionhead area near West Yellowstone:
Since yesterday up to 10 inches of snow fell in the Bridger Range, 4 inches near Big Sky, 4 inches north of Hebgen Lake, and 9 inches just south of West Yellowstone. Fortunately this new snow was deposited on a strong snowpack, and the storm started with warm temperatures which will help the new snow bond to the old snow surface. However, winds from the W and SW have been strong enough during this storm to create many sensitive wind slabs resting a weak layer of low density snow. While this type of weak layer can quickly gain strength, it will remain sensitive today and easily produce human triggered avalanches. For today, wind loaded slopes have a CONSIDERABLE avalanche danger. Non wind loaded slopes have a MODERATE avalanche danger. Don’t let your guard down today, and remember that most avalanches occur during or immediately after a storm.
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.
Upcoming Avalanche Education
1hr Avalanche Awareness - Tue, December 7, 6:30pm – 7:30pm @ REI Bozeman
Join Lucas Zukiewicz from the Montana Snow Survey for a FREE presentation/discussion on the SNOTEL system in SW Montana. The discussion will cover how to access SNOTEL information and interpret the data for snow and weather conditions. Sat, December 11, 7:30pm – 8:30pm at World Boards.
Other Events
Tonight at 6:30 p.m. – The Gallatin Valley Snowmobile Association will hold its annual Christmas party at the River Rock Community Center in Belgrade. Make plans to attend this fun event which will include silent and live auctions to raise funds for the grooming program and other GVSA supported programs.