GNFAC Avalanche Advisory for Wed Jan 10, 2018

Not the Current Advisory
This is archived for reference for a fatal accident in Idaho. The accident was not within this 
area but is close and at the time of the incident the snowpack was similar.


Good Morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on 
Wednesday, January 10th at 7:00 a.m. This advisory does not apply to operating ski areas.

AVALANCHE WARNING

The Gallatin National Forest Avalanche Center is issuing a Backcountry Avalanche Warning for the 
Lionhead area outside West Yellowstone. Over a foot of heavy, dense snow has fallen onto a weak 
and unstable snowpack. Dangerous avalanche conditions exist on all slopes and the backcountry has 
a HIGH avalanche danger. Natural and human triggered avalanches are likely. Avalanche terrain and 
avalanche runout zones should be avoided.

Mountain Weather

At 5 a.m. Cooke City, Lionhead and the Yellowstone Club have 10-12" of new snow, while other 
areas have 6-7", except Hyalite, which is has 2". Another 3-6" will fall before the storm 
dissipates mid-morning. Mountain temperatures are in the mid to high 20's, but below freezing 
(rain) in some valleys. Winds are averaging 20 mph with gusts of 30-40 mph out of the SW-W. Winds 
will decrease and shift westerly when the storm ends.

Snowpack and Avalanche Discussion - Lionhead Range

Avalanche Warning

The Lionhead area outside West Yellowstone received a foot of dense snow measuring 1.2" of snow 
water equivalent (SWE) in the last 12 hours. This is a heavy and rapid load that fell onto a weak 
and unstable snowpack. Two days ago skiers reported widespread collapsing and cracking, and 
yesterday Eric and I got poor test results in our snowpits. Today's snowfall has created dangerous avalanche conditions on all slopes for all users: skiers, snowmobilers, snow 
shoers, the avalanches do not care. People will easily trigger avalanches from the bottom of 
slopes on flat terrain. You do not need to be on the slope to trigger it. Many people have died 
in similar conditions, so to be safe, give all slopes a wide berth. The avalanche danger is rated 
HIGH and traveling in the backcountry is serious and risky.