Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on, Wednesday, February 15 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.
Before the storm ended yesterday morning an additional inch of snow fell in most locations. Winds blew westerly at 15-20 mph yesterday, but have calmed to 10 mph. Today skies will be mostly sunny, although the mountains around West Yellowstone and Cooke City will remain cloudy for most of the morning. No snow is in the immediate forecast. This morning mountain temperatures are in the single digits, but will warm to the upper teens as winds remain eerily calm.
The mountains around Cooke City:
Yesterday, the mountains around Cooke City received four inches by mid-morning. West winds moved a bit of snow and we got reports of a few natural slides on east-facing slopes (pic 1, pic 2). These slides, although small, were the second time avalanches occurred on these slopes. Repeat avalanches challenge the incorrect assumption that a slope is stable for the rest of the season once it slides.
Weak snow at the ground continues to get buried deeper making it more difficult to trigger. Another layer of weak snow formed at the surface during previous clear spells which is now buried under 1-2 feet of snow. Signs of instability will decrease quickly with our stable weather, but you’ll still be able to trigger slides on a few slopes. For today, the avalanche danger is rated CONSIDERABLE on any slope that was wind-loaded yesterday. All other slopes have a MODERATE danger.
The southern Madison and southern Gallatin Ranges and the Lionhead area near West Yellowstone:
The southern mountains got three inches of light powder yesterday. Although the snowpack is very weak it will support this new snow, especially since wind-loading is minimal. Yesterday, skiers on Bacon Rind found even better stability than their trip a week ago. The weak, faceted snowpack in these mountains will have good stability until they get a substantial snowfall (Eric’s video). If you look at the layers in Eric’s snowpit from Sunday and imagine they are children’s building blocks, it’s easy to see how they would topple. For today, it’s still not out of the question to trigger avalanches and the danger is rated MODERATE.
The Bridger, northern Madison and northern Gallatin Ranges:
Yesterday, on his day off, Eric went to Mt. Ellis and reported good stability and skiing on four inches of new snow. I toured into Beehive and Bear Basins and found plenty of facets and good stability. In an east-facing snowpit on the Bear Basin side I was able to get a layer of facets to propagate in my extended column test with a lot of whacks (23). On the Beehive side I dug into three feet of facets with a few ice crusts, but found good stability. Mark was in the Bridger Range on Friday and found a thin, weak snowpack. His snowpit showed depth hoar at the ground, near surface facets a few inches from the top, yet nothing was moving in his stability tests. He summed up his concerns in his video when his partner asks him, “So what’s your point?” and he answers, “We’re just going to have to wait and see what happens”. This recent storm was not enough to make anything “happen”. For today, the avalanche danger is rated MODERATE on slopes steeper than 35 degrees and LOW on all other terrain.
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.
NRCS Snowpack Summary Graphs
For the current state of our snowpack depth (about 70% of average on the Gallatin), check out these two graphs generated by NRCS (graph 1, graph 2).
Bozeman
FREE 1-hour Avalanche Awareness at REI on Thursday, February 16 at 6:30 p.m. For more information call REI at 406-587-1938.