GNFAC Avalanche Forecast for Sat Jan 18, 2020

Not the Current Forecast

Good Morning. This is Ian Hoyer with the Gallatin National Forest Avalanche Forecast on Saturday, January 18th at 7:00 a.m. Today’s forecast is sponsored by Bridger Bowl and Gallatin County Search and Rescue. This forecast does not apply to operating ski areas.

Mountain Weather

A fast moving storm yesterday dropped 6-9” of new snow in the Bridger and Northern Madison Ranges, 5-6” in Hyalite and near West Yellowstone, and 2” near Cooke City. Winds are southwesterly at 15-25 mph with gusts of 30-40 mph. Temperatures are single digits to low teens F and will rise into the mid-teens and low 20s F. Winds will be westerly at 25-35 mph. A trace to 2” of new snow will fall today.

Snowpack and Avalanche Discussion

New snow, strong winds, and unstable weak layers have combined to make dangerous avalanche conditions. Yesterday, Big Sky and Bridger Bowl ski patrols found the new snow avalanching easily while ski cutting during the storm. West winds drifted the new snow into cohesive slabs that will break under the weight of a skier or rider today. You will find these dangerous drifts near ridgelines and in cross-loaded gullies. Avalanches in the new snow can break 2-3 ft deep.

The new snow also added weight to the weak layers lower in the snowpack. Yesterday afternoon, a large natural avalanche broke down to the ground on a wind-loaded slope in the northern Bridger Range (photo). Another part of this bowl avalanched 2-3 ft deep on Thursday. The additional wind-loading yesterday pushed this slope over the edge and caused it to slide as well. Avalanches starting in the new snow can step down to these weak layers becoming much larger and more dangerous.

The avalanche danger is CONSIDERABLE on wind-loaded slopes. On all other slopes the avalanche danger is MODERATE.

The mountains around West Yellowstone and near Cooke City didn’t see as much new snow. Avalanches in the new and wind-drifted snow will be shallower and mostly a concern in the steepest rockiest terrain. The larger concern is the potential to trigger a big avalanche breaking deep in the snowpack. A natural avalanche was seen yesterday on an east facing slope below Lionhead Ridge (photo).

A snowmobile triggered avalanche on Henderson Mountain on Thursday broke close to 15 feet deep (details) and a very large natural avalanche broke across the whole NE shoulder of Mount Fox on Tuesday (details). Getting caught by one of these big slides would almost assuredly have devastating consequences. There is no practical way to test weak layers buried this deep. Patience is the only viable strategy. Give these weak layers more time to adjust and strengthen before getting onto steep slopes.

Large human triggered avalanches are possible and the avalanche danger is MODERATE today.

Non-wind-drifted slopes in the northern Gallatin Range are generally stable. Six inches of light snow yesterday has drifted into unstable pockets where you could trigger a slide. Be cautious on any slope where you find more than 6 or 8 inches of cohesive drifted snow. These fresh drifts will be easily triggered today. The avalanche danger is MODERATE on windloaded slopes and LOW on all others.

If you get out, please send us your observations no matter how brief. You can fill out an observation form, email us (, leave a VM at 406-587-6984, or Instagram (#gnfacobs).

Upcoming Avalanche Education and Events

Our education calendar is full of awareness lectures and field courses. Check it out and plan to attend one or two: Events and Education Calendar.


Every Friday and Saturday, Snowpack Update and Rescue Training. Friday, 6:30-7:30 p.m. at the Soda Butte Lodge. Saturday anytime between 10-2 @ Round Lake.


January 27, Avalanche Information and Demonstration Table, 10 a.m. to 12 p.m. at Montana Science Center.

January 29, GNFAC Forecaster Chat: Avalanche Myth Busters, 6-8 p.m. at Uphill Pursuits.

January 31, Women’s Only Companion Rescue Clinic, 6 - 8 pm at REI followed by a field day February 1. More info and Register Here.

February 1, King and Queen of the Ridge at Bridger Bowl (fundraiser). This is the Friends of the Avalanche Center’s second biggest fundraiser of the year. Come on out and help us raise money by hiking and skiing laps on the ridge. Prizes, camaraderie and a good time is guaranteed. Register with Bridger to hike in the event, and create a pledge page to raise funds with your Ridge laps.


January 29 and 30, Introduction to Avalanche w/ Field Course, evenings of January 29 & 30 plus a field day February 1. Snowmobile specific field day offered February 2. More Info and Register Here.


TODAY! January 18, 1-hr Avalanche Awareness, 10 a.m. to 12 p.m. at Homestake Lodge.


January 25, 1-hr Avalanche Awareness, 7-8 p.m. at West Yellowstone Holiday Inn.

February 1, 1-hr Avalanche Awareness, 7-8 p.m. at West Yellowstone Holiday Inn.


January 28, 1-hr Avalanche Awareness, 6-7 p.m. Carroll College.


January 30, Introduction to Avalanche w/ Field Course, evening of January 30 plus a field day February 2. More info and Register Here.

The Last Word

A snowmobiler was killed in an avalanche in Idaho on Wednesday, Jan 15. A video with preliminary info from the Sawtooth Avalanche Center is available here.

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