GNFAC Avalanche Advisory for Tue Jan 19, 2016

Archived - Not Current Advisory

Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on 
Tuesday, January 19, at 7:00 AM. This advisory does not apply to operating ski areas.

Mountain Weather: 

Snowfall yesterday totaled 5-7 inches in the Bridger and northern Gallatin Ranges and 3-5 inches 
everywhere else. In the last 24 hours winds have been west to southwest at 10-15 mph with gusts 
of 20 mph. This morning temperatures are in the low teens and will rise into the low 20s under 
mostly cloudy skies with winds forecasted to remain the same. Light snowfall will begin late 
tonight and drop 1-2 inches by morning. Scattered snow will continue into Wednesday.

Snowpack and Avalanche Discussion: 

Bridger Range   Madison Range   Gallatin Range  Lionhead area near West Yellowstone 

In the last three days the mountains around Bozeman to West Yellowstone have picked up over a foot 
of snow measuring 1-1.5” of snow water equivalency (SWE) with moderate westerly winds. Yesterday’s 
snowfall was denser (14%) than the previous days (10%), which create an “upside-down” or inverted 
snowpack which is unstable. Eric saw this firsthand yesterday as he was skiing north of Bridger Bowl 
during the storm and triggered a small pocket in the new snow (20’wide x 1’ deep). He made a video 
describing the current instabilities. Although filmed in the Bridger Range, his message is 
universal: new snow, inverted density, a weak layer of near-surface facets, and lingering 
instability in the depth hoar is on our minds.

On Sunday, a skier was flushed through the narrows of Wolverine Bowl in the Bridger Range when he 
triggered a powerful sluff in the new snow, and a skier in Beehive Basin triggered a small wind slab 
that same day. The weight of this new snow is also aiding propagation in the depth hoar in our 
extended column tests.  In the last four days poor test scores in Hyalite, Mt. Ellis, Frazier Lake, 
and Beehive Basin point to an increased likelihood of triggering an avalanche. Eric said, “Right 
now I would not ski anything steep… It doesn’t matter if it’s wind-loaded or not.”  For today, 
slopes that are wind-loaded or steeper than 35 degrees have a CONSIDERABLE avalanche danger. All 
other slopes are rated MODERATE.

I will issue the next advisory tomorrow morning by 7:30 a.m.