Good morning. This is Eric Knoff with an early season avalanche information bulletin issued on Saturday, November 26 at 7:30 a.m. This bulletin is sponsored by Montana FW&P Recreation Trails Grant in partnership with the Friends of the Avalanche Center. Please remember that uphill traffic is not allowed at Big Sky or Moonlight Basin Ski areas. Uphill traffic is permitted at Bridger Bowl, but backcountry snow conditions do exist. This information will be updated as conditions change.
A strong cold front pushed through southwest Montana yesterday afternoon producing strong winds and isolated snow showers. Most areas picked up 2-4 inches with the exception of the Bridger Range that received a trace to one inch. Winds were blowing 50-60 mph out of the WNW with the arrival of the frontal passage.
Currently, mountain temperatures are ranging from 5-10⁰ above zero and winds are blowing 10-20 mph out of the WNW. A ridge of high pressure will continue to build over the region today producing clear skies and warmer temperatures. Highs today will climb into the upper 20s to low 30s and winds will stay out of the WNW at 10-20 mph. Mostly sunny skies and warmer temperatures will remain over the area through Sunday.
The old Montana saying, "If you don't like the weather wait five minutes" rang true over the past 24 hours. Yesterday, a fast moving cold front turned a pleasant morning into a raging blizzard within a matter of minutes. By mid-afternoon two to four inches of snow fell in most areas, accompanied by strong-gusty winds.
Wind gusts over 60 mph were recorded in many areas, easily transporting the new snow onto leeward slopes. The predominant wind direction was WNW, meaning slopes on the eastern half of the compass likely received wind loading. In the northern ranges, wind loaded slopes will struggle to support a fresh load, due to a layer of weak-buried facets near the ground (video). Wind loaded slopes will likely fail under the weight of a skier or rider. Steering clear of wind loaded terrain will be the best way to avoid triggering or being caught in a slide.
The mountains around West Yellowstone have a shallower, but stronger snowpack (photo). Yesterday I skied in the Lionhead Area and was encouraged by what I found. Despite being on the thin side, we did not experience any cracking or collapsing of the snowpack and our stability tests produced high scores and dirty shears. However, new snow and strong winds were actively loading leeward slopes, predominately below ridgelines (video). Today, wind loaded terrain is the primary concern.
In the mountains near Cooke City, we have limited data, but we know this area has received a steady supply of snow and wind. This combination alone can easily produce avalanches.
We are not issuing avalanche danger ratings due to limited snowpack data. We need your backcountry observations to help us. Any snowpack or avalanche information is especially valuable this time of year. If you get out, please drop us a line at mtavalanche@gmail.com or leave us a message at 587-6984.
Wednesday, November 30, BOZEMAN
Introduction to Avalanches with Field Course at MSU. Wednesday and Thursday evening lectures with a field course on Saturday. More info at http://www.mtavalanche.com/education/classes/workshops
Tuesday, December 6th Beartooth Harley, Billings – Basic 1 hr Avalanche Awareness
More info at http://www.mtavalanche.com/workshops/calendar
Tuesday, December 6th 406 Brewery, Bozeman – Basic 1hr Avalanche Awareness
More into at http://www.mtavalanche.com/workshops/calendar
Wednesday, December 7th, REI Bozeman – Basic 1 hr Avalanche Awareness
More into at http://www.mtavalanche.com/workshops/calendar
Wednesday, December 7th Livingston - Snowmobiler Introduction to Avalanches with Field Course, Wednesday and Thursday evening lectures with a field course on Saturday. More info at http://www.mtavalanche.com/education/classes/workshops
Thursday, December 15th West Yellowstone – Snowmobile Guides Course. Lectures on Thursday - field day on Friday. More info at http://www.mtavalanche.com/workshops/calendar