Archived Advisory for Sun Jan 20 2008

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20 January 2008

You can listen to the advisory at:

http://www.mtavalanche.com/data/audio/Jan202008.mp3

Good morning. This is Ron Johnson with the Gallatin National Forest Avalanche Advisory issued on Sunday, January 20, at 7:30 a.m. Yamaha and Team Bozeman, in cooperation with the Friends of the Avalanche Center, sponsor today’s advisory. This advisory does not apply to operating ski areas.

MOUNTAIN WEATHER

Since yesterday morning 6-10 inches of snow accumulated in the mountains around Bozeman and Big Sky. The mountains around West Yellowstone and Cooke City got 4-6 inches. Today a cold front combined with a moist weather disturbance will deposit 6-8 inches of snow in the Bridger Range. The mountains around Big Sky, Cooke City and West Yellowstone will get 4-6 inches. Northeasterly ridgetop winds will blow 10-20 mph and mountain temperatures will be near 0 degrees F.

SNOWPACK AND AVALANCHE DISCUSSION

The Lionhead area near West Yellowstone, the mountains around Cooke City, and the Washburn Range:

On Friday, an avalanche buried and injured a snowmobiler near Cooke City. Yesterday, Doug and his partner investigated the slide. It released on a wind-loaded, south facing, 35 degree steep slope. The avalanche released on a layer of small grained faceted crystals buried 3-6 feet deep. The slide was 100 feet wide and ran 1,100 vertical feet. There is a video showing the crown fracture at:

http://www.youtube.com/watch?v=pfPrp9MjC7U

Photos are at: http://www.mtavalanche.com/photos/photos.php

The layer of faceted crystals doesn’t exist on all slopes. In fact, Doug didn’t find it on slopes adjacent to the avalanche. Not knowing where this layer exists is scary. Unless you are willing to dig snowpits and look for this layer it’s best to assume it exists on all south-facing slopes. This layer will be especially active on wind-loaded slopes. A layer of faceted crystals buried 2-4 deep also exists on Lionhead, near West Yellowstone. Today, a CONSIDERABLE avalanche danger exists on all wind-loaded slopes. A MODERATE danger exists on non wind-loaded slopes.

The Gallatin Range and Madison Ranges:

Yesterday, ski patrollers at the Yellowstone Club used explosives to release an avalanche that broke 4-6 feet deep on a layer of faceted crystals near the ground. It fractured on a wind-loaded slope. Ski patrollers at Big Sky released several soft slab avalanches on recently wind-loaded slopes. Ice climbers in Hyalite Canyon noticed collapsing and cracking of the snow around their snowshoes. Skiers on Mt. Ellis found weak faceted crystals buried under 1-2 feet of recently deposited snow. They didn’t see an obvious signs of instability because on the slopes they were skiing the new snow wasn’t cohesive enough to form a slab. A widespread layer of faceted snow buried 2-4 feet deep continues to produce avalanches, and collapsing and cracking of the snow in the Gallatin and Madison Ranges. Today the avalanche danger remains CONSIDERABLE on all recently wind-loaded slopes and on non-wind-loaded slopes steeper than 35 degrees. Non-wind-loaded slopes that are less steep have a MODERATE avalanche danger.

The Bridger Range:

Yesterday Scott Schmidt was in the Bridger Range and found good snow stability on most slopes. Ski patrollers at Bridger Bowl reported that yesterday’s new snow was denser than the fluff that fell on Friday and soft slab avalanches readily released on that interface. Skiers north of Bridger Bowl reported stable snow except on wind-loaded slopes where an avalanche released on a steep south-facing slope. Today, winds will be strong enough to form wind slabs in the Bridger Range and the avalanche danger on wind-loaded slopes steeper than 35 degrees is HIGH. Wind-loaded slopes less steep than 35 degrees and non wind-loaded slopes steeper than 35 degrees have a CONSIDERABLE avalanche danger. A MODERATE danger exists on all other slopes.

Doug 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

The ASMSU Outdoor Recreation Program sponsors a Basic Avalanche Awareness Seminar on January 23 and 24, 2008 in the SUB at MSU from 7:00 p.m. to 9:30 p.m. An all day field session will be held at Bridger Bowl on Saturday on January 26, 2008. This course is open to the public with registration at the door. Call 994-3621 for more information.

Tuesday, January 29th, Angela Patnode will present a free 1-hour Avalanche Awareness Class for women at 7:00pm at the Bozeman Public Library in the small conference room. This class is sponsored by Bozeman-based Team WinS (Women in Sports). For more information visit www.teamwins.org.