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GNFAC Avalanche Advisory for Tue Dec 22, 2009

Not Current Advisory

Good Morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, December 22 at 7:30 a.m.  Jeff King at Edward Jones, in cooperation with the Friends of the Avalanche Center, sponsor today's advisory.  This advisory does not apply to operating ski areas.

Mountain Weather: 

In the last few days temperatures warmed and the winds died down, but don't get used to it; an arctic front sweeps in late tonight.  Winds will shift from the southwest to northwest, temperatures will dip to the teens and snow will start to fall. By tomorrow morning I'm only expecting 1-2 inches, but Wednesday will be a snowy day.  In fact, if the weather models are accurate the Bridgers could get their famous northwest flow which buries the slopes in choking powder. Stay tuned.     

Snowpack and Avalanche Discussion: 

The southern Gallatin Range, the entire Madison Range, the Lionhead Area near West Yellowstone, the mountains outside Cooke City and the Washburn Range:

The mountains around Big Sky and all the ranges south have a feeble snowpack. Weak, unbonded sugary grains are straining to hold up the snows that fell over the past few weeks.  A few inches last Wednesday and Thursday was enough to trigger natural avalanches around Taylor Fork. On Sunday, Eric and I saw this widespread activity and stayed off steep slopes. Avalanches a few days old, plus a collapse as we post holed, plus clean shears in our stability tests, plus sinking to our thighs in facets clearly led us to believe we could trigger a slide.  The snowpack is so unstable that many slopes in Carrot Basin avalanched with only a few inches of snow on them. 

Video on Taylor Fork avalanches: http://www.youtube.com/watch?v=WbJHo-yfCeA

In the last five days skiers and riders have reported collapsing and cracking of the snowpack, plus recent avalanche activity.  We call these signs of instability "bull's-eye" data because their message is crystal clear: you'll likely trigger a slide.  For today, the avalanche danger is rated CONSIDERABLE on all slopes.

The Bridger and northern Gallatin Ranges:

The Bridger and northern Gallatin Ranges have weak, faceted snow too. The difference is that these ranges have not been tested by Mother Nature.  December 5 was their last substantial snowstorm. The snowpack structure is currently unstable; wind slabs at the higher elevations sitting atop sugary snow.  Last Thursday Karl and I found this recipe on Saddle Peak which we documented in a video: http://www.youtube.com/watch?v=538ihUeQaxU.  Without a new snow load I do not expect natural avalanches in the backcountry, however, it's still possible to trigger a slide given wind slabs are sitting on unstable layers.  Consequently, for today I'm rating the avalanche danger MODERATE on all slopes.

I will issue the next advisory tomorrow morning at 7:30 a.m. If you get out in the backcountry give us a call or email with your observations.  You can reach us at 587-6984 or email us at mtavalanche@gmail.com.

AVALANCHE EDUCATION

1. WEST YELLOWSTONE

Snowmobilers and Skiers: Saturday, January 2 from 12-5 pm at the Holiday Inn is avalanche lectures.  Sunday, January 3 will be an all day field session for both skiers and snowmobilers. $30 suggested donation.  No sign up required. http://www.mtavalanche.com/education/classes/snowmobilers

2. BOZEMAN

Level 1: 7-10 January, Montana Outdoor Science School is offering a Level 1 Avalanche Course. Instructors are Angela Patnode and Jay Pape.  For more information, contact Montana Outdoor Science School at 406-582-0526.

3. BOZEMAN

Level 1: American Avalanche Institute is offering a Level 1 Avalanche Course January 22-24, 2010 at Bridger Bowl. Get more information and register at: www.americanavalancheinstitute.com

4. FOUR CORNERS

Rescue Lecture:  On Tuesday, 26 January, the Gallatin Valley Snowmobile Association is having it annual Chili Feed at 6:30pm in the Groomer Shack.  At 7:00 there's a free Avalanche Rescue Talk. http://www.mtavalanche.com/workshops/calendar

5. BOZEMAN

Basic Avalanche Workshop:  The Friends of the Avalanche Center and MSU are offering a Basic Avalanche Awareness Class the evenings Wed, Thur,  27 & 28 January with a field day on Saturday, 30 January. $25 donation. No sign up required. http://www.mtavalanche.com/education/classes/basic

 

 

Video: 
Taylor Fork Avalanche
Audio: 
Audio for Dec 22, 2009