GNFAC Avalanche Forecast for Fri Dec 27, 2019

Not the Current Forecast

Good Morning. This is Ian Hoyer with the Gallatin National Forest Avalanche Forecast on Friday, December 27th at 7:00 a.m. Today’s forecast is sponsored by Yellowstone Club Community Foundation and Cooke City Motorsports. This forecast does not apply to operating ski areas.

Mountain Weather

A skiff of new snow fell yesterday morning in the Bridger’s, with no accumulations elsewhere. This morning, temperatures are in the single digits to teens F and winds are generally 10-20 mph from the southwest. High temps today will be in the teens to low 20s F. Winds will remain light out of the southwest. A dusting of snow will fall tonight, with more significant snowfall expected tomorrow night and into Sunday.

Snowpack and Avalanche Discussion

The snowpack has now had a couple days to adjust to the weight of the new snow (7-10”) that fell earlier in the week. However, with a weak faceted foundation, it will take a bit more time before the snowpack can be trusted.

Yesterday, Alex and I went to the Lionhead area to see how the snowpack had dealt with the load of new snow (video). We saw limited avalanche activity and had no cracking or collapsing. This lines up with similar reports from skiers and riders in the Madison Range. These are promising signs looking forward, but don’t change the big picture: the snowpack just got loaded and has a weak base. Triggering avalanches breaking near the ground remains a real possibility. Give it a couple more days before getting onto steep terrain. The avalanches danger is MODERATE.

Yesterday, skiers saw recent avalanches on steep, east facing, wind loaded slopes off Henderson and Sheep Mountains. Triggering avalanches is possible today, both directly beneath the new snow on windloaded slopes or on weak layers buried 1-2 ft deep. These weak layers have shown themselves to be most problematic on slopes where there are crusts around them. Adopt a two-pronged approach to deal with these concerns: dig to look for the weak layers and simply steer around the most drifted slopes to give them a little more time to settle. The avalanche danger is rated MODERATE.

The couple inches of new snow that fell this week gave the snow surface a nice refresh, but haven’t significantly impacted the avalanche conditions. The snowpack is generally stable. Still, normal caution is required.  Watch for isolated wind drifts near ridgelines where you might be able to trigger a small slide. Always carry your rescue gear (beacon, shovel, probe) and only expose one person at a time to steep slopes. For today, the avalanche danger is rated LOW.

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 4, 1-hr Avalanche Awareness, 7-8 p.m. at West Yellowstone Holiday Inn.

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


January 7, Women's Specific Avalanche Awareness + Beacons, 6-8 p.m. at Story Mill.

January 8, 1-hr Avalanche Awareness, 6-7 p.m. at REI.

January 10 & 11, Companion Rescue Clinic, 6-8 p.m. on the 10th at REI and 10-2 p.m. on the 11th at History Rock. More info and Register Here.

January 15 and 16, Introduction to Avalanche w/ Field Course, evenings of January 15 & 16 plus one field day either January 18, 19 or 25. Snowmobile specific field day offered January 25. More info and Register Here.

The Last Word

The Lionhead Weather Station is finally up and running! You can access the data here.

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