Good Morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Monday, December 6, at 7:30 a.m. The Hans Saari Memorial Fund, in cooperation with the Friends of the Avalanche Center, sponsor today’s advisory. This advisory does not apply to operating ski areas.
High pressure is dominating our weather pattern and has created strong temperature inversions. At 4 am this morning mountain temperatures are in the mid to high twenties F with the exception of Cooke City which is in the mid teens F. Winds are light are out to the W-SW at 5-15 mph. Today, mountain temperatures will reach into the low thirties F and skies will become mostly cloudy by this afternoon. West Yellowstone could see some light precipitation by this evening while the northern ranges will remain dry. No real accumulations are expected over the next 24 hours.
The Bridger, Gallatin and Madison Ranges, the Lionhead area near West Yellowstone, the mountains around Cooke City and the Washburn Range:
Calm weather over the past few days has facilitated strengthening of the recent storm snow and has helped reduce the avalanche danger. Although a few small slides were reported in the Hyalite area yesterday, a majority of our observations over the weekend point towards increasing stability. Mark skied near Hyalite peak yesterday and found no obvious weak layers in his snowpits. He did observe a few small wind slabs that released off ridgelines, but mentioned they were small in nature (photo). These small slides were confined to the new storm snow and did not step down to deeper layers.
This trend in increasing stability reaches from the northern ranges to the mountains around Cooke City and West Yellowstone. Yesterday, Doug collected our first data points in the mountains around Cooke City and reported no new avalanche activity and no obvious weak layers in the snowpack (photo).
Our main concern currently is the variety of surface layers that are forming during this period of high pressure that may become problematic layers once buried by another storm (video). As calm, clear weather helps stabilize the snowpack, a layer of substantial surface hoar is forming on the surface in many areas. These weak faceted crystals have the potential to become persistent weak layers if buried under the right conditions. The sun has also been forming a bit of a sun crust on southerly aspects, which may be of concern once buried as well.
In addition, weak faceted crystals near the ground continue to persist intermittently throughout our advisory area and backcountry travelers are advised to dig a pit and perform stability tests before riding in steep terrain.
With our snowpack trending towards stability and very little avalanche activity to speak of, the avalanche danger is rated MODERATE.
Doug 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.
Upcoming Avalanche Education
1hr Avalanche Awareness - Tue, December 7, 6:30pm – 7:30pm @ REI Bozeman
Join Lucas Zukiewicz from the Montana Snow Survey for a FREE presentation/discussion on the SNOTEL system in SW Montana. The discussion will cover how to access SNOTEL information and interpret the data for snow and weather conditions. Sat, December 11, 7:30pm – 8:30pm at World Boards.
This year REI has chosen Friends of GNFAC as their charity of choice. By making a donation through REI you can help The Friends continue to support the Avalanche Center and promote avalanche education throughout southwest MT.