Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Wednesday, December 12 at 7:30 a.m. Today’s advisory is sponsored by Helios and Knapp Sacks. This advisory does not apply to operating ski areas.
The northern mountains received a trace to one inch of new snow yesterday morning. In the southern ranges 2-4 inches fell with Cooke City picking up eight. Winds gusted into the 50s yesterday, but have dropped to 20-30 mph out of the west to southwest which is where they will remain today. At 5 a.m. mountain temperatures are in the high teens to low 20s, but will rise to the mid-20s under cloudy skies. More snow will fall today and tonight. By morning I anticipate 2-4 inches in the northern mountains and closer to six inches near West Yellowstone and Cooke City.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone
Yesterday, Mark and I drove south and rode into the Lionhead area. The snowpack was 3-4 feet deep and very supportable. We were on the hunt for weak snow, but the weakest layer we found—some grainy facets near the ground—were not much of a concern. We tromped along the ridge and jumped on wind pillows and kicked a few cornices, all with no results. The soft wind slabs were spongy and cracks would not propagate. At Big Sky the patrol ski cut sensitive wind slabs, but this instability is not widespread. On most slopes in our advisory area it’s possible to find faceted snow near the ground. However, this layer is only propagating fractures in our stability tests in some areas. Eric and I found it on Saddle Peak in the Bridger Range (video, photo), yet skiers north of the ski area in Texas Meadow did not, nor others near Bridger Peak. This type of distribution is typical and reinforces the practice of evaluating snow stability before dropping onto a slope.
With winds decreasing and only a few inches of snow falling I do not expect to see natural avalanche activity, although it’s still possible to trigger slides, mainly on wind-loaded terrain. Consequently, for today, the avalanche danger is rated MODERATE on all slopes.
The mountains around Cooke City continue to get hit with lots of snow. The additional eight inches fell onto a snowpack six feet deep. Steady loading over the past two weeks has produced only a few natural avalanches (photo). Winds have been blowing 20-40 mph out of the southwest, but as anyone who has snowmobiled or skied in this area knows, winds are swirly and seem to load slopes from every direction. With seemingly non-stop snow and wind, slopes with wind deposits are the main avalanche concern. For today, the avalanche danger is rated CONSIDERABLE on all wind-loaded slopes and MODERATE on all others.
Mark 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.
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TONIGHT, Wednesday, December 12, 1-hour Avalanche Awareness lecture at REI in Bozeman, 6:30 p.m.
TONIGHT, Snowmobiler Introduction to Avalanches with Field Course in Billings at Hi-Tech Motor Sports on December 12 and 13, 6-9 p.m. and the field course on January 20 in Cooke City. Sign up for this class HERE
Snowmobiler Introduction to Avalanches with Field Course in West Yellowstone on December 20 and 21. Sign up for this class HERE.