GNFAC Avalanche Advisory for Sat Nov 11, 2017

Not the Current Advisory

Good morning. This is Alex Marienthal with early season weather and avalanche information from the Gallatin National Forest Avalanche Center on Saturday, November 11th at 6:45 a.m. This information is sponsored by The Friends of the Avalanche Center and Yellowstone Arctic Yamaha and Yamaha Motor Corp. We will update this bulletin when conditions change.

Mountain Weather

At 4 a.m. the Bridge Range has 6-8” of new snow, mountains near Big Sky have 3”, Hyalite has 1”, West Yellowstone 5”, and Cooke City 6”. Temperatures are in the 20s F and wind is out of the southwest at 10-20 mph. Snowfall will taper off this morning with 1-2” more possible. Temperatures will reach the low 30s F this afternoon under mostly sunny skies with westerly wind at 10-15 mph. The rest of the weekend will be dry with wind increasing to 20-30 mph Sunday afternoon. Monday evening into Tuesday looks like the next chance for snow.

Snowpack and Avalanche Discussion

All Regions

At this point, a fresh layer of snow this early in the season is no surprise. The mountains have 3-4 feet of snow near Bozeman and Cooke City, and 2-3 feet near Big Sky and West Yellowstone. People have been skiing, ice climbing and snowmobiling, and have observed and triggered avalanches.

New snow last night and wind today create unstable conditions on wind-loaded slopes. Avoid avalanche terrain if you see obvious sign of instability like cracking, collapsing, and recent avalanches. I observed similar conditions at Bridger on Tuesday (video), and Doug saw drifting in Hyalite yesterday (video). On Tuesday, I easily triggered a small wind slab north of Bridger Bowl, intentionally from a safe spot. It was fairly small, but would have been inescapable, and ran through a narrow, steep, rocky chute. Avoid wind-loaded slopes, likely found near ridgelines, and assess steep terrain for consequences of even a small slide.

Last night’s snow fell on weak layers and crusts that formed over the last couple days (photo, photo). Dig down a couple feet to assess the stability of the new snow before riding in steep terrain. If the new snow easily slides or collapses, avoid similar slopes. Stability has been generally good on non-wind loaded slopes. However, it is still early and data is limited. Near Cooke City, riders observed avalanches breaking deep in the snowpack (photo), which shows deeper slides are possible on slopes that hold snow from September and October. If you plan to ski or ride in avalanche terrain, I suggest to dig multiple snowpits in similar terrain to where you plan to ride and assess the stability of deeper layers (video).

We will begin issuing daily avalanche advisories and danger ratings when the mountains get more snow. Our field data is currently limited. Besides our own field days we rely on others to help us form a picture of what’s happening across our forecast area. If you get out and have any avalanche or snowpack observations to share, drop a line via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).

Get Avalanche Smart – Episode 2: Don’t Be Like Dick

The Friends of the Avalanche Center present the second of 4 short films promoting avalanche education. Dick Aspen and Doug Chabot star in this episode to encourage you to “get the real forecast” VIDEO.

Upcoming Avalanche Education and Events

Events and Education Calendar

BUTTE

17 November, Avalanche Awareness, 6-7:30 p.m., Butte, MT

HELENA

7 November, Avalanche Awareness, 6-7:30 p.m. at Carroll College, Helena

18 November, Avalanche Awareness and Beacon Practice for Snowmobiles, 9 a.m. at Montana Boat Center, Helena

7 December, Avalanche Awareness, 6-7:30 p.m. at Basecamp, Helena

BOZEMAN

6 December, Avalanche Awareness, 6-7:30 p.m. at REI Bozeman

7 December, Avalanche Awareness and Beacon Practice, 6-8 p.m. at Beall Park, Bozeman

Nov. 29, 30 and Dec. 2, 3 or 9, Introduction to Avalanches w/ Field Day, Info and Register Here

Jan. 12 and 13, Companion Rescue Clinic, Info and Register

Jan. 17, 18 and 20 or 21, Introduction to Avalanches w/ Field Day, Info and Register Here

Jan. 24, 25 and 27, Advanced Avalanche Workshop w. Field Day, Info and Register Here

Feb. 9 and 10, Companion Rescue Clinic, Info and Register

COOKE CITY

24 and 25 November, Current Conditions and Avalanche Rescue, 6:30-7:30 p.m. Friday and anytime between 10-2 on Saturday.


Forecasters Choice Text

The best $30 you’ll ever spend, guaranteed: Our Intro to Avalanches with Field Day. Two evenings of lectures plus a full day in the field digging pits and learning about rescue. Info and Register Here


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