GNFAC Avalanche Forecast for Tue Dec 3, 2019

Not the Current Forecast

Good morning. This is Dave Zinn with the avalanche forecast for the Gallatin National Forest Avalanche Center on Tuesday, December 3rd at 7:30 a.m. Today’s forecast is sponsored by Montana State Parks and Gallatin County Search and Rescue. This forecast does not apply to operating ski areas.

*Note: Bridger Bowl is planning to open on Friday, December 6th. Uphill travel is permitted on Wednesday before closing at midnight for the season. No uphill travel will be permitted starting at 12:01 am Thursday, December 5th to allow the ski patrol a day to work the entire mountain before opening.

Mountain Weather

In the last 24 hours the mountains around the Taylor Fork, West Yellowstone, and Cooke City received 1-2” of snow with the rest of the advisory area remained dry. Mountain winds were 15-30 mph from the west and temperatures hovered around 20 F. Today, winds will be 20-30 mph from the southwest, temperatures will be in the 30s, and Cooke City could get a trace of snow.

Snowpack and Avalanche Discussion

The Lionhead, Southern Madison, and Southern Gallatin ranges received one to two feet of snow in the last week on top of a weak base. Two days ago, Doug and I went into Lionhead to assess how the snowpack is dealing with this stress. We had unstable test results and heard loud “whumping” as we walked (video). Today, obvious signs of instability will be harder to find as the snowpack adjusts and stability gradually improves. However, because we only have two field days at Lionhead, the snowpack structure is weak, and our weather data is limited, I am playing a conservative card and recommending more time before going into avalanche terrain. 

Human triggered avalanches remain likely on steep slopes and where wind deposited snow is adding weight. These avalanches could be large, and the danger is rated CONSIDERABLE. Careful route finding to avoid avalanche paths and runout zones is essential.

In the Bridger, Northern Gallatin, and Northern Madison Ranges, and the Beartooth Mountains around Cooke City the snowpack is generally stable. Those hunting for deeper instability can find it on isolated slopes and slopes with fresh drifts. Yesterday, while shoveling cornice, the Yellowstone Club Ski Patrol triggered a small avalanche that gouged down to the ground. And, on a tour to the Thone, Alex and I found unstable snow on an isolated slope with an extended column test and choose to minimize our exposure to avalanche terrain (video). These two events differ from other reports of avalanche activity this season because they failed deeper in the snowpack rather than as fresh drifts or at the new snow interface (recent avalanche activity page, video). This illustrates the importance of weighing signs of instability more than signs of stability.

Moderate winds continue today from the southwest building cornices and fresh drifts that will avalanche in specific areas. Avalanches are unlikely on slopes not affected by the wind. The danger is rated MODERATE on wind loaded slopes and LOW everywhere else. Evaluate the effect of the wind carefully and hunt for isolated instabilities with a stability test before committing to steep terrain.

Please send us your observations (no matter how brief) of avalanches, snow structure and stability, new snow amounts or wind effects. You can fill out an observation form, email us (, leave a VM at 406-587-6984, or Instagram (#gnfacobs).

Backcountry Barriers Contest

Click here to learn more about the Backcountry Barriers Contest:

We recognize that backcountry skiing can be daunting to approach. 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.


4 & 5 December, 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

Pre-register today for ASMSU’s Introduction to Avalanche Course with Field Session HERE

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