Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, March 15, at 7:30 a.m. Cliff Gullett Memorial Fund, in cooperation with the Friends of the Avalanche Center, sponsors today’s advisory. This advisory does not apply to operating ski areas.
Yesterday morning, three to four inches of snow fell in the mountains from Big Sky to the Bridger Range. In the southern half of our region, six to seven inches accumulated. With temperatures in the upper teens, winds are blowing from the west to southwest at 20-30 mph with gusts near 40 mph. Today will be partly cloudy with mountain temperatures reaching the high 20s as wind speeds increase out of the southwest. More snow tonight will measure three to five inches in the north and five to eight inches down south by sunrise.
The Bridger, the northern Madison and northern Gallatin Ranges:
In the northern mountains, yesterday’s three to four inches of new snow was gooey and measured 10-12% density. Even with winds blowing, the slabs that formed were reported to be thin and not very touchy. Winds blew last night and will continue today. Recently formed wind slabs at the ridgelines are our biggest avalanche concern and avoiding wind pillows is the easiest way to mitigate the danger. Without notable weak layers in the snowpack, I expect avalanche activity to be limited to the new snow. For today, the avalanche danger is rated MODERATE on all wind-loaded terrain and LOW everywhere else.
The southern Madison and southern Gallatin Ranges, the Lionhead area near West Yellowstone, the mountains around Cooke City and the Washburn Range:
The southern mountains have received seven inches of dense snow with steady westerly winds. Wind-loaded slopes are the primary avalanche concern and I expect some natural avalanche activity at the ridgetops today (photo). Besides windblown snow the snowpack in the south has a layer of facets a foot under the surface that may break from the new snow load. A quick hand pit should reveal its existence. This layer is not widespread. Eric found it on Bacon Rind and in Teepee Basin, while Mark and I could not find it around Lionhead. Two feet deep is another weak, thin layer of facets with sporadic distribution (video). This layer would require a heavy load to break, but with continued wind-loading today and more snow tonight, it’s worth looking for.
I recommend staying off of wind-loaded terrain and digging for these buried layers. If you find them notch back the slope angles to be on the safe side. Weak layers are under the most stress during and immediately following storms. For today, the avalanche danger is rated CONSIDERABLE on all wind-loaded terrain and MODERATE on all other slopes.
I will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations, drop us a line at mtavalanche@gmail.com or call us at 587-6984.
Avalanche Video Clip from Utah
http://youtu.be/1ynAm5Wao1I?hd=1
This is a great clip of a snowmobiler triggering a slide on March 9th in the Uinta Mountains, UT. He hurt his leg, trashed his machine, but should recover fine. Watching the clip a few things stand out:
1. Small slopes can be dangerous, especially when slides push you into trees.
2. His helmet cam shows how fast even a small slide accelerates.
3. Partners watching from a safe zone are worth their weight in gold.