Archived Advisory for Tue Jan 22 2008

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TUESDAY, JANUARY 22

Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, January 22nd, at 7:30 a.m. The Yellowstone Club, in cooperation with the Friends of the Avalanche Center, sponsor today’s advisory. This advisory does not apply to operating ski areas.

MOUNTAIN WEATHER

Yesterday was the first day in the last seven without any new snow in our advisory area. Under clear skies the temperatures stayed below 0F, bottoming out to -20F near West Yellowstone and Cooke City. Yesterday, around Big Sky, ridgetop winds blew from an unusual northeast direction, while in the Bridger Range they were more south and east. Today, under increasing clouds, winds will blow from the northwest, temperatures won’t rise much more than 0F and we should see 1-2 inches of new snow by morning.

SNOWPACK AND AVALANCHE DISCUSSION

The Gallatin Range and Madison Ranges:

On Sunday, a skier was killed in a large avalanche he triggered in Beehive Basin located just north of Big Sky. The slope was sw facing and wind loaded. The avalanche was 1 ½ to 3 feet deep, 600 feet wide and ran approximately 1,800 feet down the slope. The victim and his partner dug 2 snowpits nearby and although they found faceted snow a foot off the ground, it was not fracturing easily in their tests. They also watched a group of 4 ski the slope all at the same time (!) on slightly lower angled terrain. The lower part of their tracks were wiped out by the subsequent slide—they were one lucky group!

Check out 2 aerial photos of the slide at: http://www.mtavalanche.com/photos/photos.php

The snowpack in these mountains is thin and weak. Scott Schmidt investigated the slide yesterday and found very different depths and stability within a short distance. His weakest and most unstable snowpit was only 2 feet deep. Faceted snow near the ground broke very clean with minimal force. The skiers likely found a similar spot when they triggered the slide. These variable conditions are the heart of the matter. We are not finding widespread natural avalanche activity on these deep layers, however, skiers and snowmobilers are certainly able to trigger them. It’s insidious and a bit scary. I recommend limiting your turns to lower angled terrain. And please, ski or ride slopes one at a time, carry rescue gear and practice with your transceiver. So far this winter we’ve had four live recoveries with transceivers!

In other areas of the Gallatin and Madison Ranges, we are still seeing signs of instability. Skiers on Mt Ellis, outside Bozeman, got collapsing and cracking on wind-loaded terrain near the ridgetop. The snowpack here is weak, faceted and resembles the snow we’ve seen at other human triggered avalanches on Yellow Mountain and south of Lone Peak. Today the avalanche danger remains CONSIDERABLE on all slopes steeper than 35 degrees AND on any slope with a wind-load. Lower angled slopes not affected by the wind will have a MODERATE danger.

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

Over the last several days skiers in the mountains outside West Yellowstone have found great turns on easterly aspects, but a layer of faceted, sugary snow 1 ½ feet off the ground has caused them some concern. Consequently, they’ve been sticking to lower angled terrain, especially in light of the northeast winds which freshly wind-loaded some slopes.

Outside Cooke City, wind-loaded terrain, especially on south aspects, is unstable. On Friday a snowmobiler was caught in a slide that fractured on a layer of faceted snow 2 feet off the ground. We found this layer on south facing slopes on Scotch Bonnet and Mount Abundance too. I investigated the slide on Saturday and made a video clip of my findings which you can watch at:

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

For today, a CONSIDERABLE avalanche danger exists on all wind-loaded slopes. A MODERATE danger exists on all other slopes.

The Bridger Range:

On Sunday, east winds scoured the top 200 feet of the ridge in the Bridger Range. All this new snow was dumped onto the west side which naturally triggered an avalanche that ran over a thousand vertical feet. Since last Wednesday close to 45 inches of snow has fallen. Winds rotated around the compass and loaded many slopes, some of which do not normally see wind loads. For today, the avalanche danger is CONSIDERABLE on all wind-loaded slopes. On slopes without wind loading the danger is MODERATE if they are steeper than 35 degrees and LOW everywhere else.

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

The ASMSU Outdoor Recreation Program sponsors a Basic Avalanche Awareness Seminar on this Wednesday and Thursday 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