Good morning. This is Doug Chabot with an early season avalanche information bulletin issued on Saturday, November 19 at 7:30 a.m. This bulletin is sponsored by Montana Import Group. 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 exist. Our next bulletin will be issued Monday morning.
In the northern areas 2-3 inches of snow fell last night as temperatures plummeted to below zero. In the southern mountains 4-6 inches fell with temperatures dropping to the single digits. Winds have been averaging 10-15 mph out of the west with gusts hitting 30 mph. High pressure will build today and temperatures will climb towards normal in the next few days. Other than a few flurries this morning I’m not expecting more snow this weekend. Unfortunately, Thanksgiving week looks to be dry too.
It’s bad. Folks are triggering avalanches from low angled terrain which are propagating far and wide. Slopes that held early season snow are especially dangerous since the old snow became weak, faceted and sugary. With 1-2 feet of new snow this week it’s difficult to tell which slope is unstable and which is not.
Yesterday, very experienced backcountry skiers were shocked when they triggered a slope in Hyalite from low angled terrain. There were no previous collapses or natural avalanche activity to warn them of the high instability. The slope collapsed and a fracture propagated 2-300 feet uphill breaking two feet deep and a few hundred feet wide. Adjacent slopes cracked too. Skiers in Big Bear in the northern Gallatins triggered a large slide on Wednesday that was spooky because it ran very wide, even across ridge lines. This past week avalanches were reported in Beehive/Bear Basins; outside Cooke City, in the Fingers at Bridger Bowl and during avalanche control at Big Sky. All these slides are breaking on large, sugary facets. Plain and simple, this activity indicates we have unstable snow on many slopes in our forecast area.
Although our snowpack data is sparse, we know enough.
- Avalanches are being triggered from low angled slopes.
- Slopes that held old snow now have unstable snow.
- Cracking and collapsing are bulls-eye data that the snowpack is unstable (photo).
Human triggered avalanches are likely during the next two days. It’s unfortunate that as soon as we get enough snow to ski the conditions are dangerous. The most inviting slopes, those with the deepest snowpack, will also be the most likely to avalanche.
A special note to ice climbers: Hyalite’s high elevation gullies likely have faceted, unstable snow capped by thick wind drifts from cross-loading. Be extra cautious this weekend.
A special note to Bridger Bowl skiers: The ski area is closed and has not done avalanche control. Although the terrain may feel safe because of your familiarity with it, the conditions are identical to the backcountry. Early season avalanches at ski areas are not uncommon. Jamie Pierre, a professional skier, died in Snowbird, UT last week on a backcountry snowpack within the ski area boundaries.
We are not issuing avalanche danger ratings yet because we only have 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