Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Thursday, March 26, at 7:30 a.m. Cooke City Motorsports and Yamaha in partnership with the Friends of the Avalanche Center sponsor today’s advisory. This advisory does not apply to operating ski areas.
Since yesterday morning 1-2 inches of snow fell near Bozeman and Big Sky where temperatures were in the mid 20s F with westerly winds blowing 15-30 mph. Further south this morning, temperatures were a few degrees cooler and westerly winds were blowing 10-20 mph. Today will have clouds and some sunshine this afternoon. Temperatures will warm into hi 30s to low 40s F and winds will blow 10-20 from the W. A ridge of high pressure will move over the area tomorrow bringing warm temperatures and more sunshine.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
Monday and Tuesday delivered the biggest storm since February 21 with about a foot of new snow that fell on an ice crust on most slopes except N facing ones. If heading out today, the only question to ask is: How well is the new snow bonding to the old snow surface? Answer this question by testing small slopes and performing quick stability tests.
Karl Birkeland and his partners found good and bad answers to this question while skiing south of Bozeman in Hyalite Canyon yesterday. They found a layer of small facets under the new snow on a NNE aspect (9200 ft) that broke easily and propagated fractures in stability tests (ECTP16, 11). They did not find this layer on a SE aspect where the new snow bonded well to the old snow (video).
Yesterday riding just south of Big Sky, my partner and I found a good bond between the old and new snow (video). There were some small avalanches that occurred on Tuesday involving the new snow, but this instability mostly healed. Our main concern was that wet slides in the new snow could occur tomorrow. Ski guides near Cooke City, a skier near Hyalite on Mt Ellis, and Eric on his day off in the Absaroka Range outside the advisory area all found stable conditions. Eric did find a slightly faceted layer under the new snow but it would not break in stability tests.
Watch for two things today. (1) Look for fresh wind slabs from increased winds overnight mostly near Bozeman and Big Sky. (2) Look for slopes with an isolated weak layer of facets, mainly on north aspects. These facets produced an avalanche last Thursday in the Bridger Range on a NE aspect (video). Overall stability is pretty good, but heightened avalanche conditions on certain terrain features mean human triggered avalanches are possible and the avalanche danger is MODERATE.
I 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.