Good Morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Friday, March 21 at 7:30 a.m. Montana Import Group, in partnership with the Friends of the Avalanche Center, sponsors today’s advisory. This advisory does not apply to operating ski areas.
Snowfall started early this morning at Bridger Bowl. By 7 a.m. 6 inches of very low density snow had fallen at the top of the Bridger lift, and Big Sky got a dusting. All other areas were dry. Temperatures this morning had dropped into the single digits and low teens F with light winds blowing 10-15 mph from the WNW at ridgetops. Today will be similar to yesterday but winds will be light. High temperatures will be near 20 F and winds should only blow 5-10 mph. Snowfall in the Bridger Range should end soon with another few inches falling.
Bridger Range Gallatin Range Madison Range
Lionhead area near West Yellowstone Cooke City
Watch for wind slabs near ridgetops following strong SW winds yesterday. This problem is simple because we can see and avoid it. A more difficult problem is facets buried deep in the snowpack that have produced large avalanches (article and video on deep slabs). Yesterday the Big Sky Ski Patrol spotted a recent large slide on a NE aspect of Fan Mountain. It was likely triggered by a falling piece of cornice and occurred on part of the mountain that avalanched previously.
Yesterday riding near Carrot Basin and Skyline Ridge in the southern Madison Range, Doug and I spotted an avalanche (photo) that occurred early this week. It is a good example of where avalanches can be triggered: slopes steeper than 35 degrees in areas with a relatively thin snowpack. Exposed rocks provide good clues for areas with thin snow. Recent large slides near Cooke City have occurred where slope angles are greater than 35 degrees near rocks and thin snow.
The odds of triggering a large avalanche on facets near the ground are low but the consequences are high. There are two ways to lower the odds. 1) Give the snowpack time. It has only 3 days since the last load of new snow. Each day without snow the odds go down. Tuesday morning near Big Sky and Hyalite 1.5-2 feet of snow fell. Other areas received much less snow. 2) Choose terrain less than 35 degrees in steepness with an even and consistently deep snowpack.
Today the avalanche danger is rated MODERATE. Triggering a slide isn’t guaranteed but continued avalanche activity tells us that it is definitely possible.
Eric 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.
UPPER HYALITE ROAD CLOSURE
Beginning today, the Hyalite road beyond the dam will be closed to motorized use. The Hyalite Road from the mouth of the canyon to the Blackmore Day Use site remains open. Read more in this press release.
ACCIDENT REPORTS
10 March, Altoona Lakes Fatality (by West Central Montana Avalanche Center)
11 March, Crown Butte Fatality
15 March, Mount Abundance Injury
BLOG POSTS
Check out our latest Blog Posts. Mark wrote about the deep slab avalanche problem. Eric wrote an article about what it takes to put out an avalanche forecast and Doug recapped some lessons from the Beehive avalanche incident in February that was published in Carve.