Friday, January 18, 2008 Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Friday, January 18th, at 7:30 a.m. Gallatin County Search and Rescue, in cooperation with the Friends of the Avalanche Center, sponsor todays advisory. This advisory does not apply to operating ski areas. MOUNTAIN WEATHER Call in sick with a case of powder flu today and head to the Bridger Range which received 15 inches of snow since yesterday morning at 7AM. The mountains around Big Sky and Cooke City received 2-4 inches overnight, while the mountains around West Yellowstone have been dry. Temperatures are in the single digits this morning and winds are blowing 25-30 mph in the Bridger Range and 10-20 mph in the mountains around Big Sky. Today, winds will blow 15-25 mph from the northwest and mountain temperatures will hardly break into the double digits. A moist, unstable northwest flow will continue and bring an additional 4-5 inches of snow in the Bridger Range and 2-3 inches in other areas with snowfall amounts decreasing further south. This snowfall will taper off by early this afternoon, but I expect more snow to start by tomorrow morning. SNOWPACK AND AVALANCHE DISCUSSION The Gallatin Range and Madison Range: Yesterday in the backcountry near the Yellowstone Club, a skier triggered an avalanche which caught and fully buried her on a 36-37 degree, non-wind loaded slope. Her partners quickly located her with avalanche transceivers, saw a ski tip poking out of the snow, and dug her out alive and uninjured just as she was beginning to turn blue. This avalanche was about 100 ft wide and 120 ft vertical, and it ran on a layer of weak faceted snow about 1 ft above the ground. This layer of faceted snow has been responsible for numerous avalanches in the Gallatin and Madison Ranges. While skiing on Ernest Miller Ridge yesterday, my partner and I found several, similar weak layers in the snowpack combined with a slab resting on top of them. These are key ingredients for an avalanche. As my partner began to ski down the low angle terrain, the entire slope collapsed telling me these weak layers are near their breaking point. Similar signs of instability combined with recent avalanche activity show that the snowpack remains unstable and human triggered avalanches are very probable. For today, the avalanche danger is CONSIDERABLE on slopes steeper than 35 degrees and less steep, wind-loaded slopes. All other slopes have a MODERATE avalanche danger. The Lionhead area near West Yellowstone, the mountains around Cooke City, and the Washburn Range: Some avalanche activity has also occurred in the Lionhead area near West Yellowstone and the mountains around Cooke City, but stable conditions have also been found. Only a few inches of snow have accumulated in these mountains since yesterday, but recent storms have provided lots of snow for winds to deposit on leeward slopes. Recent, wind deposited snow on steep slopes will probably avalanche with the added weight of a human trigger. Buried layers of faceted snow also exist, and Doug found these layers in the mountains near Cooke City to be a bit stronger than similar layers in other mountains. However, he felt it was still possible to trigger a slide on these layers. For today, the avalanche danger is CONSIDERABLE on all wind loaded terrain steeper than 35 degrees. All other avalanche terrain will have a MODERATE danger. The Bridger Range: The Bridger Bowl Ski Patrol reported strong northwest winds at the ridgetops and strong north winds at lower elevations. These winds are readily moving the 15 inches of new snow and beginning to form some wind slabs. These wind slabs are resting on very low density snow and should easily fracture. This type of instability is short lived, but you will need to watch out for it today as these wind slabs continue to grow. For today, the avalanche danger on wind-loaded terrain is rated CONSIDERABLE if its steeper than 35 degrees and MODERATE on lower angled terrain. Slopes not affected by the wind will have great skiing and a LOW avalanche danger.