Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Friday, December 5 at 7:30 a.m. Today’s advisory is sponsored by Bridger Bowl in partnership with the Friends of the Avalanche Center. This advisory does not apply to operating ski areas. Bridger Bowl is now open for the season and uphill travel is not allowed.
Since yesterday morning the mountains near Cooke City received 6 inches of snow while all other areas received 1-2 inches. Winds calmed this morning and were blowing 10-15 mph from the W and SW with temperatures in the mid to high 20s F. The sun should appear this afternoon with high temperatures near 32 degrees F. Winds will remain about the same. A little bit of snow may come late Saturday.
Cooke City
In the past two days the mountains near Cooke City have received 1.1 inches of snow water equivalent. Mild temperatures and steady snowfall may improve stability in the long run. A layer of weak facets about 8-12 inches above the ground appears to be gaining strength as it adjusts to the weight of 3-4 feet of snow on top of it.
The odds of triggering avalanche have decreased BUT it’s hard to know exactly how much. Local guides have not seen any recent, natural avalanche activity, and their stability tests have shown a general strengthening trend. However, this weak layer of facets was responsible for a fatality on November 26th and a full burial on November 28th, and there was an Avalanche Warning in effect only five days ago. Don’t trust this layer yet.
With more snowfall continuing to add stress to the snowpack, the danger is rated CONSIDERABLE on slopes steeper than 35 degrees. Because the odds of triggering an avalanche have decreased to some degree, the danger is rated MODERATE on less steep slopes.
Bridger Range Gallatin Range Madison Range
Lionhead area near West Yellowstone
Yesterday the Big Sky Ski Patrol triggered more avalanches with both explosives and ski cuts on facets near the ground on north facing slopes. An experienced observer nearby got unstable results in his stability tests mostly on slopes with a northerly aspect, but his general impression is that the snowpack is highly variable right now: stable on some slopes; unstable on others.
My partner and I saw similar conditions further south in the Taylor Fork area where we found plenty of weak facets 4-8 inches above the ground. We got both unstable (ECTP’s) and stable (ECTN’s) results in our stability tests. The Bridger Bowl Ski Patrol has also triggered more avalanches with explosives as they hunt for pockets of instability.
Mild weather is slowly helping the snowpack gain strength as Karl Birkeland found on Tuesday in the Bridger Range (video) but this strengthening is not happening uniformly on all slopes. You might trigger an avalanche on one slope but not on another. Because it’s possible to trigger an avalanche today, the avalanche danger is rated MODERATE .
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.
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 EDUATION and EVENTS
Take a look at our Education Calendar for all our classes being offered.
Avalanche Awareness (1-hour), Wednesday, December 10, 6:30 p.m. at REI, Bozeman
Avalanche Awareness (1-hour), Thursday, December 11, 6 p.m. at Summit Motorsports, Bozeman
Weather Workshop, Thursday, December 11, 6:30 p.m. at REI, Bozeman
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.