Thursday, December 6 Good Morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Wednesday, December 6 at 7:30 a.m. Sweet Pea Landscaping, in cooperation with the Friends of the Avalanche Center, sponsor todays advisory. This advisory doesnt apply to operating ski areas. Bridger Bowl Ski Area is not yet open for the season and backcountry conditions exist within their boundaries. MOUNTAIN WEATHER Overnight 2-4 inches of new snow fell and ridgetop winds blew 10-20 mph from the west. Temperatures returned to cooler conditions near 20 degrees F. A moist westerly flow today will continue to bring 1-2 inches of snow while the mountains around Cooke City will get 2-4 inches. Ridgetop winds will continue to blow from the west at 20 mph and mountain temperatures will be in the upper teens. Later today, temperatures will begin to drop as cold air moves in from the north. SNOWPACK AND AVALANCHE DISCUSSION The southern Gallatin and Madison Range, the Lionhead area near West Yellowstone, the mountains around Cooke City and the Washburn Range: Yesterday, Doug and I checked out a massive avalanche that partially buried and injured a snowmobiler on Scotch Bonnet Mountain, just north of Cooke City. I was amazed with the size of the avalanche and the distance over which the fracture propagated. The 2-3 foot crown line was over a mile wide, and the avalanche ran 1500 vertical feet on south to east aspects. Numerous natural avalanches have occurred on Henderson, Sheep, Miller, Mineral and Republic Mountains. We experienced widespread collapsing which never ceases to scare the heck out of me. Even though we were tempted with great riding conditions, we carefully avoided terrain over 30 degrees and even flat terrain connected to steep slopes because we felt it would be easy to Bonnet at http://www.youtube.com/watch?v=zuc45gxLBc4 In the southern mountains, the snowpack is still straining from Mondays snowfall. With the combination of new snow and weak, faceted crystals, the snowpack expressed its discontent to Doug and Scott with widespread collapsing and cracking in the Lionhead area. They also saw evidence of many natural avalanches which is a clear indication of instability. View a video clip of their stability test at http://www.youtube.com/watch?v=5AILMR8KxyU The mountains around Big Sky have not been immune to recent instabilities. While at Big Sky on Tuesday, I watched an entire slope fracture and avalanche under the weight of one person who cautiously approached the edge of the slope. Near treeline other avalanches have occurred naturally on facets near the ground. Above treeline many avalanches have been triggered on a layer of facets formed during last weeks cold weather. The widespread natural and human triggered avalanche activity is a clear sign of unstable snow. If you venture into the backcountry today, avalanches are likely on steep slopes or even terrain connected to steep slopes. For today, the avalanche danger remains HIGH on all slopes steeper than 35 degrees and CONSIDERABLE on less steep terrain. The Bridger Range and northern Gallatin Range: The Bridger and Northern Gallatin Range hasnt received as much snowfall as other areas. With less stress on the snowpack, less avalanche activity has been observed. Caution is still warranted, as an ice climber triggered a small wind loaded slope near G1 in Hyalite Canyon on Monday. Ski patrollers at Bridger Bowl were also able to trigger avalanches on steep, wind loaded slopes. Today a CONSIDERABLE avalanche danger exists on recently wind loaded slopes steeper than 35 degrees. A MODERATE danger exists on all other slopes.