Good Morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Friday, November 26, at 7:30 a.m. The Yellowstone Club Community Foundation, in cooperation with the Friends of the Avalanche Center, sponsor today’s advisory. This advisory does not apply to operating ski areas. Please remember uphill traffic is not allowed at any of the ski areas today.
Today will be a good one to get outside after yesterday’s feast. Overnight, temperatures warmed into the low teens F and will reach 20 degrees F today under a mix of some sun and clouds. Winds were blowing 15-30 mph from the W in most areas except in the Bridger Range where winds were blowing 40 mph yesterday and 30 mph this morning. Today, ridgetop winds will continue blowing 15-30 mph from the W. Over the past 2 days 3-5 inches of low density snow has fallen, and late this evening a few snowflakes should fall but not accumulate.
The Bridger, Gallatin and Madison Ranges, the Lionhead area near West Yellowstone, the mountains around Cooke City and the Washburn Range:
Despite recent cold weather, our limited dataset shows that the snowpack seems to have been deep enough to avoid significant faceting and weakening. In many areas the snowpack is “right-side up” meaning it is dense and supportable near the ground and less dense and powdery near the surface. Yesterday Doug observed these conditions on Lionhead near West Yellowstone, Eric saw similar conditions on Mt. Ellis in the northern Gallatin Range, and I found similar conditions in Beehive Basin near Big Sky. However, some faceted layers can be found near the ground especially on slopes above treeline. Skiers near Mt Blackmore in Hyalite Canyon found this layer reactive in stability tests (ECTP25) in one pit but not the other (ECTX) and did not ski their intended line, a wise decision. Until we get more data, look for faceted layers near the ground and assess their strength and ability to propagate fractures. Even though some faceted snow can be found, the primary avalanche problem is dense wind-blown snow resting on low density snow (photo). Strong westerly winds blew during the past two days forming many wind slabs on the lee sides of ridges. The Big Sky Ski Patrol triggered these fresh wind slabs yesterday with ski cuts and explosives but found them mostly reactive in steeper areas. Fortunately surface slabs are easy to identify and avoid. For today the low density snow under these slabs will fracture and produce human triggered avalanches on wind loaded slopes where the avalanche danger is rated CONSIDERABLE. Slopes not affected by the wind have a MODERATE avalanche danger. Eric 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 Basic Avalanche Awareness – Wed & Thurs, December 1 & 2, 7:00pm – 9:30pm at SUB Ballroom B&C; 12/4- Field day at Bridger Bowl (more information) (Prepay $25 fee) Avalanche Awareness for Snowmobilers – Wed & Thur, December 1 & 2, 7pm – 9:30pm at Team Bozeman, 2595 Simmental Way and a field session either Sunday, Dec 5th or 12th depending on snow (more information)