GNFAC Avalanche Forecast for Fri Dec 25, 2020

Not the Current Forecast

Good Morning. This is Ian Hoyer with the Gallatin National Forest Avalanche Forecast on Christmas Day, Friday, December 25th at 7:15 a.m. This forecast is sponsored by Montana State Parks and Yellowstone Club Community Foundation. This forecast does not apply to operating ski areas.

Mountain Weather

It seems that southwest Montana must have been on Santa’s naughty list this year - which is to say, there is no new snow to report. Winds have been 10-20 mph with gusts of 20-40 mph out of the south and west. Temperatures this morning are teens to high 20s F. Winds will continue at 10-20 mph today out of the southwest under partly sunny skies. Temperatures will rise into the 20s and low 30s F. A few snow flurries tonight won’t leave much accumulation.

Snowpack and Avalanche Discussion

Weak, sugary snow at the ground has been struggling to accommodate the load of snow piled on top of it by the last storm. As new snow fell and strong winds built a slab, there were both natural and human triggered avalanches (photo, details, avalanche activity list). As we get further out from the loading event, the snowpack is getting less touchy, but triggering a slide is still possible on any slope where a cohesive slab developed (video). The snowpack structure remains poor. We don’t trust it and neither should you. Unfortunately, the weak layers near the ground won’t heal quickly. Natural avalanches seen yesterday on Bridger Peak are a good example of the sort of slide you could trigger today (photo). 

Watch for signs of instability - recent avalanches, collapses, or cracks shooting out in front of you. If you see any of these signs, reevaluate plans to get into avalanche terrain. If you don’t see any obvious signs, dig down to keep searching for instability in the snowpack before committing to steep slopes (video). As triggering avalanches remains possible, the avalanche danger is MODERATE today.

Our primary concern around Cooke City is avalanches breaking under the new snow on wind-loaded slopes. While Cooke City got the most snow out of this last storm (over 2 ft of snow measuring 2.2” snow water equivalent), it fell on a snowpack without widespread weak layers. During the storm earlier in the week, many natural avalanches broke on steep, rocky, wind-loaded slopes (video, video). It is getting harder to trigger one of these slides, but remains possible. Stay safe by steering around the steepest, rockiest, most windloaded areas near ridgelines. The avalanche danger is MODERATE today.

If you get out, please send us your observations no matter how brief. You can submit them via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).

Upcoming Avalanche Education and Events

See our education calendar for an up to date list of all local classes. Here are a few select upcoming events and opportunities to check out:

Every Saturday in Cooke City, FREE snowpack update and rescue practice at the Round Lake Warming Hut between 10 a.m. and 3 p.m. Poster with More Info.

January 20 & 21 (plus field sessions the following weekends), Avalanche Fundamentals with Field Course. There are separate field sessions tailored for both skiers and splitboarders (Bridger Bowl) and snowmobilers (Buck Ridge). Register here.

The Last Word

There have been four avalanche fatalities in the mountains of CO and WY since last Friday. We are deeply saddened by these events. You can find preliminary reports at https://avalanche.state.co.us/accidents/us/