Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Thursday, December 11 at 7:30 a.m. Today’s advisory is sponsored by a Montana FWP Recreation Trails Grant. This advisory does not apply to operating ski areas.
A deepening trough of low pressure off the west coast will bring warm and windy weather today and precipitation Friday night. This morning temperatures were near 30 degrees F except in the Bridger Range where they were in the mid 40s F. Winds increased overnight and were blowing 20 mph from the S and SW gusting 30-50 mph. Today will have more sunshine and temperatures in the 30s and 40s F with continued strong, southerly winds.
Bridger Range Gallatin Range Madison Range
Lionhead area near West Yellowstone Cooke City
Warm temperatures and no new snow have greatly reduced the odds of triggering an avalanche. BUT, conditions are highly variable. Most observations indicate a fairly stable snowpack at the moment because the snowpack has not been stressed by the weight of new snow. However, the snowpack continues showing signs that triggering an avalanche on some slopes remains possible.
- Yesterday skiers on Mt Blackmore in Hyalite Canyon just south of Bozeman experienced some collapsing, cracking, and one good whumpf of the snowpack: very clear signs of an unstable slope.
- At the same time, Doug and his partners were ice climbing in Hyalite Canyon above Silken Falls where they found a more stable snowpack (video) but they did find faceted snow crystals near the ground that could cause an avalanche.
- The Yellowstone Club Ski Patrol tested their snowpack for the first time of the season with explosives and triggered many full path avalanches on slopes that had not released naturally around Thanksgiving.
A quick recap of the last month to understand the situation: Extreme cold temperatures during the second week of November created weak, faceted crystals near the ground on all slopes (check all our recent snowpits). Heavy snowfall around Thanksgiving stressed this layer and caused avalanches to break at the ground. Since then, warm temperatures and minimal snowfall allowed the snowpack to stabilize on many slopes but at different rates. Some slopes are strong and stable, others are weak but stable (due to a lack of loading), and a few remain unstable.
Don’t take anything for granted and assess facets at the ground on every slope. While the danger may vary widely from one slope to the next, the avalanche danger overall is rated MODERATE.
The weak layer at the ground should be tested before hitting a steep slope. Doug just wrote an article posted on our blog titled “Put Your Shovel in the Snow!” which explains this in more detail.
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.
Have a Smartphone or Tablet? The Friends of the Avalanche Center just published two FREE apps so you can get the latest avalanche information, videos and photos: iOS 8 GNFAC App; Android app
AVALANCHE EDUCATION and EVENTS
Take a look at our Education Calendar for all classes being offered.
TONIGHT: Avalanche Awareness (1-hour), Thursday, December 11, 6 p.m. at Summit Motorsports, Bozeman
TONIGHT: Weather Workshop, Thursday, December 11, 6:30 p.m. at REI, Bozeman (http://www.rei.com/event/62227/session/102926)
Fundraiser at Katabatic Brewing, Tuesday, December 16, 4-8 p.m., Livingston
Avalanche Awareness and Beacon Practice, Wednesday, December 17, 6:30-8:30 p.m. at Beall Park, Bozeman
Snowmobiler Introduction to Avalanches with Field Course
West Yellowstone: Dec 18 and 19, 2014: https://www.ticketriver.com/event/12955
Five hours of lectures are followed by a full day field course. Topics covered include: avalanche terrain recognition, the affect weather has on avalanche hazard, the development of the mountain snowpack, decision making skills, and basic search and rescue procedures.