14 December 2007

 Good Morning. This is Ron Cruddy Cartilage Johnson with the Gallatin
 National Forest Avalanche Advisory issued on Friday, December 14 at
 7:30 a.m. Sweet Pea Landscaping, in cooperation with the Friends of
 the Avalanche Center, sponsor todays advisory. This advisory does not
 apply to operating ski areas.


 MOUNTAIN WEATHER

 Yesterday 12-18 inches of sweet, fluffy powder snow accumulated in the
 Bridger Range above about 7500 feet. About 6 inches accumulated at
 6000 feet. The mountains around Big Sky, West Yellowstone and Cooke
 City got less than 2 inches. Yesterday mountain temperatures were near
 10 degrees F and west-northwest ridgetop winds blew 10-20 mph.


 Today a high pressure ridge will move over southwest Montana. A few
 snow showers could occur over the northern mountains though snowfall
 amounts will be less than 1-2 inches. Otherwise, skies will be partly
 cloudy, west-northwest ridgetop winds will blow 20-30 mph and mountain
 temperatures will be in the teens to low 20s F

 SNOWPACK AND AVALANCHE DISCUSSION

 The Bridger Range and northern Gallatin Range:

 Yesterday ski patrollers at Bridger Bowl reported the density of the
 new snow was only 2 percent and this low density snow readily produced
 loose snow avalanches. Today, wind speeds will increase and wind slabs
 will readily form on the lee side of ridges and gullies. These slabs
 will be sensitive especially on steep slopes. Today a CONSIDERABLE
 avalanche danger exists on wind-loaded slopes steeper than 35 degrees.

 Less steep wind-loaded slopes have a MODERATE danger. A
 MODERATE danger also exists on non wind-loaded slopes steeper than
 35 degrees while a LOW danger exists on less steep non wind-loaded
 slopes.


 The Northern Madison Range

 In the Madison Range, north of Big Sky, faceted snow buried about
 a foot deep is a weak layer that produced widespread avalanches,
 and collapsing and cracking of the snowpack last week. This week
 avalanches on this layer were mostly on wind-loaded slopes. Today a
 CONSIDERABLE avalanche danger exists on wind loaded slopes steeper
 than 35 degrees. A MODERATE danger exists on all other slopes.


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

 In the mountains south of Big Sky, and in the mountains around West
 Yellowstone and Cooke City, the avalanche danger remains CONSIDERABLE
 on all wind-loaded slopes, while non wind-loaded slopes have a
 MODERATE danger. The weak layers responsible for these danger
 ratings are faceted snow near the ground around West Yellowstone
 and faceted snow in the middle of the snowpack in the mountains
 around Cooke City. These layers have a history of producing
 avalanches, and collapsing and cracking of the snowpack as recently as
 last weekend.