GNFAC Avalanche Advisory for Sun Feb 26, 2017

Not the Current Forecast

Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Sunday, February 26th at 7:00 a.m. Today’s advisory is sponsored by Mystery Ranch and Montana Ale Works. This advisory does not apply to operating ski areas.


ISSUED ON FEBRUARY 26 2017 at 7 a.m.

The Gallatin National Forest Avalanche Center is issuing a Backcountry Avalanche Warning for the Bridger Range. Heavy snowfall and strong wind over the last 36 hours has created a HIGH avalanche danger on all slopes. Natural and human triggered avalanches are likely today. Avalanche terrain and avalanche runout zones should be avoided.

This warning will expire or be updated by 6:00 a.m. on February 27, 2017.

Mountain Weather

The Bridger Bowl cloud is back for breakfast and might stick around today. At 7 a.m. the Bridger Range picked up 7” of snow in the last 2 hours. The mountains got 1-2” of snow yesterday after the Bridger Range got over 2 feet of classic cold smoke powder Friday night. Temperatures this morning are single digits above and below zero to low teens F. Overnight, west wind was 35-45 mph at Bridger and 15-25 mph with gusts of 40 mph elsewhere. Today, temperatures will be single digits to low teens F with west wind at 10-25 mph. Intermittent snow showers through tonight will add 3-6” by tomorrow morning with Ullr only knows how much in the Bridgers.

Snowpack and Avalanche Discussion

Bridger Range

Two to four feet of low density snow blanketed the Bridger Range yesterday and will continue today. Wind increased through the day and formed hefty wind slabs over 3’ thick. Yesterday, skiers on the Throne witnessed a natural avalanche (photo) and a skier near Fairy Lake triggered a large wind slab (photo, photo). Wind slabs grew larger overnight and are easy to trigger and will run naturally today. Avoid steep slopes and be extra cautious of runout zones. Eric was at the Throne yesterday and urged caution with this new snow for a couple days (video).

Two to four feet of snow is a hazard regardless of wind. In steeper terrain, dry loose snow avalanches are easy to trigger and can gain enough volume to carry or push a skier over. Today, avalanche danger is HIGH on all slopes.

Madison Range   Gallatin Range   Lionhead area near West Yellowstone

The mountains south of Bozeman to West Yellowstone got 10-20” of new snow over the last week. Recent west-southwest wind drifted snow into 1-2’ thick slabs that are are possible to trigger today. Cornices have matured with recent snow and wind, and hang far off ridgelines over steep slopes. Give these monsters a wide berth along ridgelines and be cautious of slopes below.

Larger avalanches are possible on layers of facets buried 1.5-3’ deep. Avalanches broke on these facets at Lionhead last week (photo, photo, video). I found unstable test results on this layer at Bacon Rind on Friday (snowpit), and yesterday skiers near Hebgen Lake backed off a slope after finding similar results. Dig 3-4 feet down to assess this layer before riding steep slopes. It can be found with a quick stability test and exists above a hard rain crust on slopes below 9,000’. Avalanches are possible to trigger today and avalanche danger is MODERATE.

Cooke City

Near Cooke City, average snow depth is around 9 feet and there aren’t any widespread weak layers. Primary instabilities are recent wind slabs formed by west to southwest wind. These slabs are likely near ridgelines and possible to trigger today. Slabs could range from 1-3’ thick. Be cautious of recently wind loaded slopes, especially in high consequence terrain.

Avalanches deeper in the snowpack are unlikely, but possible in isolated areas, possibly on steep, rocky slopes where the snowpack is relatively shallow. Avalanche danger is MODERATE on wind loaded slopes and LOW elsewhere.

I will issue the next advisory tomorrow morning by 7:30 a.m.

We rely on your field observations. Send us an email with simple weather and snowpack information along the lines of what you might share with your friends: How much new snow? Was the skiing/riding any good? Did you see any avalanches or signs of instability? Was snow blowing at the ridgelines? If you have snowpit or test data we'll take that too, but this core info is super helpful! Email us at or leave a message at 406-587-6984.

Upcoming Events and Education

Beacon Training Park at Beall: Open and free to the public for avalanche beacon practice seven days a week from 9 a.m. to 8 p.m., southeast corner of Beall Park in Bozeman (photo).


Weekly rescue training and snowpack update, 6:30-7:30 p.m., Soda Butte Lodge on Friday, Lulu Pass Road for field location Saturday (Look for the yellow sign).


March 1, 1-hr Avalanche Awareness, 6-7p.m., REI Bozeman.

March 4, Pinhead Classic, Proceeds to benefit Friends of GNFAC. More info here.