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GNFAC Avalanche Advisory for Tue Mar 9, 2010

Not Current Advisory

Good Morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, March 9, at 7:30 a.m.  The Dance Center, in cooperation with the Friends of the Avalanche Center, sponsors today's advisory.  This advisory does not apply to operating ski areas.

Mountain Weather: 

Sunny skies have exited and a weak system resembling winter will roll in tonight. Mountain temperatures are currently in the high teens to low twenties with light 5-10 mph winds blowing east-southeast.  Speeds will remain light, but the direction will swing to the south then westerly as the system tracks over Montana. Temperatures will remain cooler and only reach the mid twenties today.  Clouds will increase bringing snow showers tonight. By morning 1-2 inches will fall in the southern mountains and only one inch in the north.  Looking further out, light snow ends tomorrow and high pressure returns on Thursday bringing sun and above normal temperatures.  Ouch.

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:

A few things are happening to our snowpack from the recent drought and relative heat wave.  First off, the facets at the ground are strengthening.  Eric found this in Taylor Fork in the southern Madison Range on Saturday and also near Frazier Lake in the Bridger Range yesterday. Second, without new snow adding stress, the avalanche activity has decreased.  And third, the snow surface will likely become our most prominent weak layer once it gets buried.  Throughout southwest Montana we're finding similar crystals and crusts at the surface.  Any aspect other than due south has a mixture of small grained facets, aka recycled powder, or small ½ inch sized surface hoar crystals.  These are sitting on ice crusts on many slopes.  Once buried these grains will become unstable and cause avalanches. 

Reports from the Bridger Range, Mt Ellis, ski areas at Big Sky, the Beaver Creek area in the southern Madison Range, and Cooke City are all reporting similar things: weak surface snow, crusts, and variable skiing and riding conditions.  Eric got clean shears two feet deep in his compression tests on small facets in the Bridger Range while further south in Beaver Creek a skier found the same thing.  Although it's taking more force to break this layer, it's still reactive in some spots.  I did not find it last week in Beehive Basin, nor did Mark see it near Cedar Mountain, both in the northern Madison Range.  The current variability indicates that it's strengthening, but it's a good idea to dig down to see if it's there.  For today, the avalanche danger remains MODERATE on all slopes throughout southwest Montana. 

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.

Audio: 
Audio for Mar 9, 2010