SPECIAL ANNOUNCEMENT - AVALANCHE WARNING
The Gallatin National Forest Avalanche Center is issuing a Backcountry Avalanche Warning for the southern Gallatin and southern Madison Ranges, the Lionhead area near West Yellowstone, the mountains around Cooke City and the Washburn Range in northern Yellowstone National Park. New snow over the last 36 hours was deposited on an extremely weak snowpack. Today the avalanche danger in HIGH on all slopes. Areas of unstable snow exist. Natural and human triggered avalanches are likely. Avalanche terrain including avalanche runout zones should be avoided.
This statement supercedes the advisory below. Check back tomorrow morning at 7:30 a.m. for updated information.
Happy New Year! This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Friday, January 1, at 7:30 a.m. On Site Management, in cooperation with the Friends of the Avalanche Center, sponsor today's advisory. This advisory does not apply to operating ski areas.
2010 has started with a bang. Since yesterday morning the mountains near West Yellowstone and Cooke City received 6-8 inches of snow, the mountains near Big Sky received 3-6 inches, and the mountains near Bozeman got 3 inches. This morning temperatures are in the teens F with ridgetop winds blowing 10-20 mph from the W and SW. Today temperatures will climb to near 20 degrees F and winds will remain the same but increase this afternoon as snowfall returns. By tomorrow morning the mountains near West Yellowstone will get 4-6 inches of snow, the mountains near Cooke City and Big Sky will get 2-4 inches, and the mountains near Bozeman will receive 1-3 inches.
The Madison and southern Gallatin Ranges, the Lionhead Area near West Yellowstone, the mountains around Cooke City and the Washburn Range:
New snow has added significant stress to the fragile snowpack in mountains near Big Sky, West Yellowstone and Cooke City where weak faceted snow exists near the ground. In many areas skiers or riders will break through upper layers of snow and sink into these facets which will be obvious. In other areas like Cooke City, a supportable layer of snow will keep you from seeing these facets until you pull out your shovel and dig a few feet down. Another less obvious layer of facets formed at the snow surface during several warm sunny days and clear cold nights just after Christmas. Yesterday skiers in Beehive Basin experienced collapsing of the snowpack a sure sign of instability, and the Big Sky Ski Patrol found fresh wind slabs up to 1 foot deep. With more snow since then, the snowpack is more unstable and wind slabs are even bigger.
The combination of new snow and buried weak layers means avalanches will occur especially on wind loaded slopes. Today, natural and human triggered avalanches are likely on wind loaded slopes where the avalanche danger is rated HIGH. Sheltered slopes without wind drifted snow may not produce many natural avalanches, but human triggered avalanches are probable in this terrain where the avalanche danger is rated CONSIDERABLE.
The Bridger and northern Gallatin Ranges:
Yesterday Doug, Eric and I skied in the backcountry near Bridger Bowl on both the west and east sides of the range. Our snowpits were full of facets. Even old wind drifts once containing dense snow were totally faceted and weak. Though the powder was only an inch or two deep it felt much deeper because the snow surface faceted during warm sunny days and clear cold nights just after Christmas. These near surface facets made the skiing good but made the skinning difficult. Skiers in Hyalite Canyon yesterday found surface hoar crystals that formed during the same time. In either case recently formed wind slabs will easily fracture on these weak layers and possibly trigger a bigger and more deadly avalanche. Not all slopes in the Bridger and northern Gallatin Ranges have such a faceted snowpack, but these slopes will take work and expert assessment skills to find.
Today, human triggered avalanches are probable on recently wind loaded slopes where the avalanche danger is rated CONSIDERABLE. Sheltered slopes without a wind load have a MODERATE avalanche danger.
I will issue the next advisory tomorrow morning at 7:30 a.m. If you get out in the backcountry give us a call or email with your observations. You can reach us at 587-6984 or email us at mtavalanche@gmail.com.
AVALANCHE EDUCATION
1. WEST YELLOWSTONE
Snowmobilers and Skiers: Saturday, January 2 from 12-5 pm at the Holiday Inn is avalanche lectures. Sunday, January 3 will be an all day field session for both skiers and snowmobilers. $30 suggested donation. No sign up required. http://www.mtavalanche.com/education/classes/snowmobilers
2. BOZEMAN
Level 1: 7-10 January, Montana Outdoor Science School is offering a Level 1 Avalanche Course. Instructors are Angela Patnode and Jay Pape. For more information, contact Montana Outdoor Science School at 406-582-0526.
3. BOZEMAN
Level 1: American Avalanche Institute is offering a Level 1 Avalanche Course January 22-24, 2010 at Bridger Bowl. Get more information and register at: www.americanavalancheinstitute.com
4. FOUR CORNERS
Rescue Lecture: On Tuesday, 26 January, the Gallatin Valley Snowmobile Association is having it annual Chili Feed at 6:30pm in the Groomer Shack. At 7:00 there's a free Avalanche Rescue Talk. http://www.mtavalanche.com/workshops/calendar
5. BOZEMAN
Basic Avalanche Workshop: The Friends of the Avalanche Center and MSU are offering a Basic Avalanche Awareness Class the evenings Wed, Thur, 27 & 28 January with a field day on Saturday, 30 January. $25 donation. No sign up required. http://www.mtavalanche.com/education/classes/basic