10-11

The Bridger Range and northern Gallatin and Madison Ranges

A skier in Beehive and Middle Basins yesterday (Sunday) noticed isolated patches of surface hoar. It was obvious at or just below the ridge line, mostly on easterly aspects, but not down low. Photo: Anon

An honest three to four feet of snow is blanketing our forecast area. The snowpack around West Yellowstone and Cooke City doubled in depth this past week and will likely get deeper with this week’s storms. Over the weekend there were many sluffs naturally releasing and running long distances. Wind slabs were noted on the ridgelines throughout the north, but generally these stayed put. Skiers in Beehive Basin saw widespread wind slabs in the upper elevations and chose to stick near treeline.

In three days a little over an inch of snow water fell from Big Sky to the northern Gallatin and Bridger Ranges totaling 16 inches of snow. Most of our observations are from folks skiing in the Bridger Range. Our biggest concern is wind-loaded slopes near the ridgetop where folks triggered a few pockets in the last two days.

Let’s recap the recent weather.  Just before this storm on Thursday, westerly winds blew up 60-80 mph (video), scouring some slopes and forming stiff wind slabs on others. Since Thursday night, 1.5 to 2 feet of low density snow fell in most areas while Cooke City received nearly 3 feet. During much of this storm, winds were blowing 15-30 mph from the W slowing backing to the SW until they calmed this morning. 

Yesterday 60-80 mph winds (video) scoured some slopes and formed stiff, meaty slabs on others. Two avalanches were observed at the north end of Bridger Bowl (which is not open, not patrolled, and has backcountry conditions) as they ripped down Hidden Gully onto the Apron below. These appeared to be skier triggered and confined to recently formed wind slabs. With new snow overnight, these wind slabs will remain sensitive to human triggers today and be our primary concern.

Since Sunday the mountains have received 15-20 inches of dense snow with over 2 feet falling in the upper bowls of Hyalite Canyon. This snow combined with snowfall from last week and the end of October has created a solid foundation for the rest of the winter. Much can change in coming weeks, but we’re off to a good start and looking pretty good.

Just over 3 ft of settled snow as of November 16th can be found in the Bridger Range immediately north of Bridger Bowl.  The main layer of concern is a combination of graupel crystals and heavily rimed, new snow crystals.  A slightly denser layer of snow rests on top.  These two layers are easy to find and will easily produce an avalanche if loaded by wind blown snow.