10 January 2008

 Good morning. This is Ron Johnson with the Gallatin National Forest
 Avalanche Advisory issued on Thursday, January 10, at 7:30 a.m.

 Northern Lights Trading Company, in cooperation with the Friends of
 the Avalanche Center, sponsor todays advisory. This advisory does not
 apply to operating ski areas.


 MOUNTAIN WEATHER

 Yesterday the mountains of southwest Montana were dusted with 1-3
 inches of new snow. Overnight westerly ridgetop winds in the Bridger
 Range and southwesterly ridgetop winds near Big Sky blew 15-30 mph.

 During the next 24 hours, a small weather disturbance will deposit 1-3
 inches of snow in the northern mountains. The mountains around West
 Yellowstone and Cooke City will get 2-4 inches. Today westerly
 ridgetop winds will blow 20-30 mph and mountain temperatures will
 reach the teens to low 20s F.


 SNOWPACK AND AVALANCHE DISCUSSION

 The Bridger Range:

 Ski patrollers at Bridger Bowl found yesterdays couple of inches of
 new snow wasnt blown around and no wind slabs formed. However, winds
 did increase overnight and wind slabs should be expected on the lee
 side of ridges and gullies. A party skiing in the northern Bridger
 Range found surface hoar buried about 6 inches deep but only on
 north facing slopes. This layer produced propagating fractures on
 wind-loaded slopes. Karl Birkeland dug a snowpit on a north facing
 slope near Bridger Bowl. Buried surface hoar didnt exist in his
 pit, which lacked any significant weak layers. Today wind slabs could
 fracture on buried surface hoar or low density new snow;
 therefore, a MODERATE avalanche danger exists on wind-loaded slopes
 steeper than 35 degrees. All other slopes have a LOW danger.


 The northern Gallatin Range and northern Madison Range:

 In the mountains south of Bozeman including those around Big Sky, on
 slopes where total snow depth is less than about 3 feet, weak faceted
 crystals exist near the ground. They are found mid-pack in deeper
 snow. These crystals have been responsible for recent cracking and
 collapsing of the snowpack as well as both human triggered and
 naturally released avalanches. The existence of these weak layers
 combined with addition of 4-6 inches of new snow during the past two
 days means a CONSIDERABLE avalanche danger exists on all slopes
 steeper than 35 degrees. A MODERATE danger exists on less steep
 slopes.


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

 Yesterday Doug Chabot and Mark Staples rode around the Taylor Fork,
 Sage Creek and Cabin Creek areas of the southern Madison Range. They
 continue to be concerned about the stability of snow especially on
 wind-loaded slopes. The primary weak layer is small grains of
 faceted snow buried beneath wind slabs. This layer is buried 1-3
 feet deep and also exists in the mountains around West Yellowstone and
 Cooke City. Today for these areas a CONSIDERABLE avalanche danger
 exists on all wind-loaded slopes. A MODERATE danger exists on non
 wind-loaded slopes.