Good Morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Wednesday, March 26 at 7:30 a.m. Grizzly Outfitters in partnership with the Friends of the Avalanche Center sponsors today’s advisory. This advisory does not apply to operating ski areas.
Mountain temperatures hit the mid-forties yesterday and have cooled into the high twenties to low thirties overnight under cloudy skies. Ridgetop winds have been 15-20 mph out of the west to southwest and will remain the same. At 5 a.m. it started raining in Bozeman and snowing in the mountains; about an inch of snow has fallen at the ski areas. Temperatures will cool and scattered rain and/or snow will fall throughout the day. Freezing line will be around 5-6,000 feet as a moist southwest flow drops 2-4 inches up north and 4-6 inches in the south.
Bridger Range Gallatin Range Madison Range
Lionhead area near West Yellowstone Cooke City
This winter our mountains have fared well with a snowpack measuring 8-12 feet deep about 110-140% of average. Every storm created a new layer and we spent countless hours checking the bonds between these layers to determine stability. Yet here we are late in the season coming full circle: large facets that formed at the ground (depth hoar) in early December is the same layer we are worried about now. Although deep and difficult to trigger, it is certainly not impossible. I backed off a slope on Monday in the northern Bridger Range because of this layer breaking in my tests (photo) and yesterday Mark made a video from Bacon Rind describing the problems these facets pose throughout our area. They are most unstable during and immediately after a storm, are triggered from thinner areas adjacent to deeper slopes and will not strengthen anytime soon. Yesterday a skier reported a couple of older, large avalanches that ran at the ground on the northerly aspects of Mount Blackmore—bulls-eye data that avalanches are still possible.
This morning the avalanche danger is starting out as MODERATE on all slopes, but could rise to CONSIDERABLE if today’s rain and wet snow continues.
Deep Slab Avalanches Explained (sort-of):
Mark wrote a short article on deep slabs and we also made a video outlining why they are so dangerous and what to look out for.
Mark 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.
Our last daily avalanche advisory will be Sunday, April 6th. If conditions warrant we will issue intermittent advisories the following week.