GNFAC Avalanche Advisory for Sun Feb 28, 2010

Not the Current Advisory

Good Morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Sunday, February 28, at 7:30 a.m.  Hans Saari Memorial Fund, in cooperation with the Friends of the Avalanche Center, sponsor today's advisory.  This advisory does not apply to operating ski areas.

Mountain Weather

A split jet stream has diverted energy from a strong pacific low to the north and south of Montana leaving our area in a cloudy but dry doughnut hole.  Although we are picking up residual pieces of energy from this strong pacific storm, only a trace of new snow has fallen over the southern portion of our advisory area in the past 24 hours.  Today, temperatures will remain above average with highs in the 40's and lows in the 20's and winds will stay fairly light out of the S-SW at 10-15 mph.  We can expect to see clearing skies and more warm temps by tomorrow.

Snowpack and Avalanche Discussion

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

We have reached the seventh inning stretch of the 2009-2010 winter season.  Now is a good time to stretch our minds, reflect on the events of this season and think about what may be to come.  We know we have had below average snowfall to this point, but we have had above average avalanche activity for the season.  A shallow snowpack often means a weaker snowpack and this winter has been no exception.  Weak facets near the ground have persisted throughout the season and serve as a poor foundation for both the existing snowpack and for the snow that is yet to fall.  This persistent weak layer is still capable of failing and propagating a fracture, although triggering it is becoming more challenging with time.  If you do tickle this sleeping dragon in the right place, you can expect to be confronted with a deep avalanche with devastating consequences.  Other weak layers within the pack that will be easier to trigger are layers of surface hoar and near surface facets that exist 1-2 feet below the surface.  These sensitive weak layers are now being found on most slopes throughout our advisory area and will more likely fail under the stress of a skier or rider, especially in upper elevation areas that have received recent wind loading during the earlier part of the week.  This weak layer was responsible for a human triggered avalanche near Cooke City on Wednesday.   

Yesterday I skied off the west side of Saddle Peak in the Bridger Range and found both facets near the ground and near surface facets 1.5 feet below the surface easy to detect in my snowpits.  Both these weak layers produced clean shears with moderate to heavy force during stability tests.  Although the snowpack is showing signs of strengthening, my partners and I did not fully trust it and skied slopes less than 35 degrees.  As February leaves like a lamb, the Lion waits just around the corner.  With March statistically being the snowiest month of the year, we can expect to see more snow and more avalanche activity before this season is over.  In the meantime, practice with your rescue gear and don't let your guard down.  The winter is far from over.  Despite a lack new snow, weak layers in the snowpack continue to hold the possibility of failing under the stress of a skier or rider and human triggered avalanches remain possible.  For today the avalanche danger is rated MODERATE.

I will issue the next advisory tomorrow morning at 7:30 a.m. If you get out in the backcountry let us know what you find.  You can reach us at 587-6984 or email us at mtavalanche@gmail.com.

Avalanche Education & Events

1.    Bozeman

Join us to discuss the snowpack, weather, and circumstances leading up to the avalanche on Saddle Peak.  We will show videos, pictures, and share stories about this popular sidecountry destination. Cost: Free, When: Thursday, March 4 from 6:30-7:30 p.m., Where: Bozeman Public Library meeting room.

2.    Bridger Bowl

29th Annual Pinhead Classic on Saturday, March, 6th.  "Carnival" is this year's costume theme, so come dressed up to race, socialize and win great prizes. Registration fee is $30 but gets you all sorts of cool stuff. Check out the website http://pinheadclassic.com for details.

3. Moonlight Basin

Comprehensive avalanche awareness class - Thursday, March 4th to Saturday, March 6th

events@moonlight.com or 406-993-6026


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