Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Wednesday, December 23, at 7:30 a.m. Today’s advisory is sponsored by Yellowstone Arctic Yamaha and Yamaha Motor Corp. This advisory does not apply to operating ski areas.
Cooke City, Sheep Mountain Avalanche Accident Report: http://www.mtavalanche.com/sites/default/files/151219_Sheep%20Mountain%20Avalanche%20Report_Public.pdf
Last night 3-4 inches fell in Big Sky and Bridger Bowl which was in addition to the 1-2 inches that fell everywhere early yesterday morning. Winds are currently blowing W-SW at 10-15 mph with gusts of 25 mph. Temperatures this morning are in the single digits and will rise into the low 20s under mostly cloudy skies. Scattered showers today will only drop an inch of snow with westerly winds blowing 10-20 mph at the ridgetops. Cold temperatures, flurries and light winds are on the docket for the next couple of days.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
As the snowfall and winds subside, so does the avalanche danger. Yesterday’s avalanche warning for the southern mountains has expired, but conditions are far from safe. Large avalanches were reported in Teepee Basin in the southern Madison Range yesterday along with the Big Sky Ski Patrol releasing a deep avalanche off the north summit snowfield with explosives (size R4, D4). Not to be left out, Saddle Peak naturally avalanched during the pre-dawn hours yesterday, pulling out tracks from the days before and likely sparing the lives of future skiers (Osama Bin Pow talked about this in 2010 and the video is worth watching again). Consider this: one inch of new snow and some wind was all it took to tip the scales and avalanche. There is still acreage in the backcountry, both on Saddle Peak and elsewhere in our forecast area, where avalanches have not yet occurred but are ripe for human-triggers.
Over the last two weeks many feet of snow fell, measuring 5-6” of snow water equivalency (SWE) in the southern mountains and 3-4” of SWE in the northern ranges. This is a lot of weight. Weak snow crystals of facets and depth hoar at the ground could not support this load and many avalanches were reported and documented on our Photo and Video pages. Over the last week we had natural and human triggered slides in every mountain range. An avalanche fatality outside Cooke City on Saturday (video, photo) was a sad reminder that when the snowpack is very unstable people can trigger avalanches from low-angled terrain, even the flats, if the slope is connected to steeper terrain.
The snowpack is unstable and weak (video). Traveling in avalanche terrain is dangerous and requires careful route-finding and snowpack assessment; without these skills you will likely trigger an avalanche. For today, the danger is rated CONSIDERABLE on all slopes throughout our forecast area.
Alex will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations to share, drop us a line at mtavalanche@gmail.com or leave a message at 587-6984.
EVENTS and AVALANCHE EDUCATION
A complete calendar of classes can be found HERE.
TONIGHT, Cooke City: December 23, 1hr Avalanche Awareness, Cooke City Visitor’s Center, 6-7:30 p.m.
West Yellowstone: January 2, 1hr Avalanche Awareness, West Yellowstone Holliday Inn, 7-8:30 p.m.
Bozeman: January 6, Women’s Avalanche Awareness and Beacon 101, Beall Park, 6-8 p.m.
January 9 and 10, Companion Rescue Clinic, REI, Fri 6-8p.m., Sat 10a.m.-2p.m.
January 13, 1hr Avalanche Awareness, REI, 6-7:30 p.m.
Livingston: January 14, 1hr Avalanche Awareness, Neptune’s Brewery, 6-7:30 p.m.
Dillon: January 19, 1hr Avalanche Awareness, UM Western Library, 6:30-8 p.m.
ASMSU Intro to Avalanches w/ Field Course
January 20, 21 and 23 or 24: https://www.ticketriver.com/event/16861
The workshops will be held on Wednesday and Thursday evenings, with a field course on either Saturday or Sunday. Different topics will be presented each evening. Topics include: avalanche terrain recognition, the effect weather has on avalanche hazard, the development of the mountain snowpack, decision making skills, and basic search and rescue procedures.