GNFAC Avalanche Forecast for Wed Dec 4, 2019

Not the Current Forecast

Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Forecast on Wednesday, December 4th at 7:00 a.m. Today’s forecast is sponsored by Grizzly Outfitters and Your Montana Chevy Dealers. This forecast does not apply to operating ski areas.

*Note: Bridger Bowl will open this Friday. No uphill travel will be permitted starting at 12:01 a.m. Thursday, to allow the ski patrol to prepare the entire mountain for opening.

Mountain Weather

This morning, under partly cloudy skies mountain temperatures are in the high teens to low 20s F and winds are blowing west-southwest at 10-20 mph with gusts of 40 mph in the Bridger Range. There’s no new snow to report, nor is there any forecasted in the immediate future. Today will be mostly sunny with mountain temperatures reaching the low 30s and southwest wind blowing 15-25 mph.

Snowpack and Avalanche Discussion

The mountains south of Big Sky to West Yellowstone have the weakest snow in our forecast area. Near the ground a layer of sugary, faceted snow (called depth hoar) struggles to support the snow from the weekend. Dave and I had this layer collapse with an audible “whumph” many times in Lionhead, and Ian and I had the same yesterday in Taylor Fork. A whumph is an avalanche on flat terrain and bullseye information the snow is unstable. Without new snow in the forecast this weak layer will become less reactive to triggering; however, like a bad case of diaper rash, it will be problematic for weeks to come.

For today, the avalanche danger is rated MODERATE since we are still seeing signs of instability and it is possible to trigger avalanches.

Yesterday the Bridger Bowl Ski Patrol triggered large avalanches on a few heavily wind-loaded slopes at the ridgeline. These were hard slabs of wind-packed snow that traveled 1000’ downhill (pic3, pic4). They broke 2-4 feet deep and ran on a crust that formed early in the season. The size of these slides caught us off guard. We were not expecting them to run that deep. Patrollers triggered the slides as they cut and shoveled cornices. Although these were triggered in the Bridger Range, the Yellowstone Club Ski Patrol and Big Sky Ski Patrol are also finding wind-loaded slopes to be problematic and I have no reason to think otherwise in the northern Gallatin Range or around Cooke City. Heavily wind-loaded terrain is avalanche prone. Without a wind-load slopes are generally stable, yet isolated areas could harbor weak snow. Dave and Alex found this in the northern Bridger Range which they detected with a stability test (video).

For today, the avalanche danger is rated MODERATE on all wind-loaded 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).

Island Park

The mountains south of Big Sky to West Yellowstone have the weakest snow in our forecast area. A layer of sugary, faceted snow (called depth hoar) near the ground is not very strong and struggles to hold up the snow from the weekend. Without new snow in the forecast this layer will become less reactive to triggering, but it will be slow to strengthen. Signs of instability like “whumphs” or recent avalanches are warnings to not enter avalanche terrain.

Backcountry Barriers Contest

Click here to learn more about the Backcountry Barriers Contest:

We recognize that backcountry skiing can be daunting. That’s why Ben Goertzen and the Friends of the Gallatin National Forest Avalanche Center have teamed up to help breakdown some of the most prominent barriers of entry to backcountry skiing through this campaign. One lucky winner will be given a complete backcountry skiing kit, a spot in an avalanche awareness course, and featured in a three part video series that ends with an excursion into the backcountry with professional skier and filmmaker, Ben Goertzen. These videos will be used by the Friends of GNFAC to help other aspiring backcountry skiers gain awareness, knowledge and start to breakdown their barriers to entry.

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.


TONIGHT and TOMORROW, Introduction to Avalanche w/ Field Course, Evenings of December 4 & 5 plus one field day either December 7, 8 or 14. Snowmobile specific field day offered December 14. More info and Register Here.

December 11, 1-hr Avalanche Awareness, 6-7 p.m. at REI.

December 12, Avalanche Awareness + Beacon Practice, 6-8 p.m. at Story Mill Community Center.


9 & 10 December, Snowmobile/Ski Introduction to Avalanche w/ Field Course, 12-5p Dec 9 and field day Dec 10. More info and Register Here.


December 9, 1-hr Avalanche Awareness, 7-8 p.m. at Manhattan High School.


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.

The Last Word

The Gallatin Valley Snowmobile Association deserves a shout-out for putting up new beacon checkers at Taylor Fork and Buck Ridge Trailheads.

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