Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, March 6 at 7:30 a.m. A Montana Fish Wildlife & Parks Recreation Trails Grant sponsors today’s advisory. This advisory does not apply to operating ski areas.
This morning mountain temperatures are in the mid-20s after hitting the low 40s yesterday. Winds are still blowing west to southwest at 30-40 mph, but were blustery yesterday afternoon with gusts reaching the high 50s. A fast moving cold front with snowfall is hitting Bozeman as I type this at 6:00 a.m. Temperatures will drop into the upper teens, winds will remain steady out of the west to southwest and the mountains will get a few hours of intense snowfall. I expect 4-6 inches will accumulate before skies clear tonight. High pressure and sunny skies are on the menu for the rest of the week.
The Bridger, Madison and Gallatin Ranges, the mountains around Cooke City and the Lionhead area near West Yellowstone:
Above freezing temperatures and direct sun melted the surface snow on east and south aspects during the last two days. Wet avalanche activity was minimal and last night’s cold temperatures refroze the surface. The ski patrols around Big Sky and an observer in Cooke City reported winds were strong enough to load slopes; no small feat given the high density (ie. creamy powder) of the surface snow. Moonlight Ski Patrol reported these new wind slabs were adhering well to the old snow surface. This is good news, but our real concern is with deeper layers. A thin layer of faceted snow about two to three feet deep is found on most slopes throughout our advisory area. It’s definitely getting stronger and will continue to get more difficult to trigger, but we can’t forget it’s there. Sitting near the ground on some slopes is depth hoar--large chains of sugary facets. On Sunday, these were breaking clean in my stability tests at the top of Truman Gulch on the backside of Bridger Bowl (video, photo). Although prevalent in the Bridger Range, we are also finding these on other slopes with a thin snow cover (Cooke City being the exception).
Snowmobilers triggered two avalanches on Cedar Mountain on Sunday and a few more on Buck Ridge over the weekend (photos). A few natural slides were seen in this area too, one yesterday low down in the trees on an east facing slope. Skiers in the southern Madison Range got a slope to avalanche from a cornice drop on Saturday. This slide released on depth hoar at the ground and had likely avalanched earlier.
Wind loads, especially with today’s new snow, will add stress to these weaker layers. During and immediately after a storm are when the snowpack is the most sensitive to triggering. For today, especially in light of today’s new snow and wind, the avalanche danger is rated CONSIDERABLE on all wind-loaded slopes. All other slopes will have a MODERATE avalanche danger.
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.
Events/Education
Come to Bridger Bowl on Saturday, March 17th (St. Patrick’s Day) with telemark skis, AT skis, alpine skis, snowboards, split boards, or even snow blades. The theme is Snowpocalypse based on the wildly popular Mayan 2012 apocalypse. $30 gets you into the races, a pint glass, t-shirt, a good time, a raffle ticket, and food by Cafe Fresco. Pre-register at Mystery Ranch or Grizzly Ridge March 11-16. Visit http://pinheadclassic.com/ or the Pinhead Facebook page for more info.
1-hour Avalanche Awareness at REI, Bozeman
Tuesday, March 20 at 6:30 pm. Sign up for this FREE class here.