Good Morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Saturday, March 27, at 7:30 a.m. Northern Lights Trading Company, in cooperation with the Friends of the Avalanche Center, sponsors today's advisory. This advisory does not apply to operating ski areas.
Since yesterday morning most areas received an additional trace of snow, and skies began clearing overnight. This morning temperatures dropped into the mid teens F with winds blowing 10-25 mph from the NW. Today will be mostly sunny with high temperatures in the low to mid 30s F. Winds will decrease to 10-15 mph and slowly shift to the W. No more snow will fall this weekend, but it should return by Monday evening and the rest of next week looks promising.
Wet Snow Avalanche Danger
Today's weather will start quite cold but warm rapidly under mostly sunny skies and calm winds. Wet snow avalanches will be limited, but south facing slopes with new snow sitting on a hard ice crust may heat enough for a few loose, wet snow slides (photo). By afternoon the wet snow avalanche danger should rise to MODERATE on all sun exposed slopes.
The Bridger Range:
With 8-9 inches of heavy snow (about 1 inch of snow water equivalent) and strong winds in the Bridger Range, yesterday was a good one for avalanches including two on Saddle Peak. While these slides were confined to fresh wind slabs and did not break deeper, they contained a surprising amount of snow and ran far. Despite this activity some skiers traversed through these obvious signs of instability to reach fresh powder, a poor decision. Luckily no one was caught or injured. Ski patrollers at Bridger triggered many avalanches about 12-18 inches deep, and Eric and I observed several natural avalanches near Sacajawea Peak. We also found a layer of facets 1.5 feet deep that was reactive in our stability tests (video) and produced a few subtle collapses.
Last night strong winds continued to blow, making wind loaded slopes the primary avalanche concern. Today slopes steeper than 35 degrees with wind-blown snow have a CONSIDERABLE avalanche danger. All other slopes have a MODERATE avalanche danger.
The Gallatin and Madison Ranges, the Lionhead area near West Yellowstone, the mountains around Cooke City and the Washburn Range:
Similar conditions exist in the rest of the advisory area: new snow, strong winds, and avalanches. Ski patrollers on Lone Mountain triggered many soft slab avalanches with some running over 1000 ft. A few avalanches on N aspects were remotely triggered, meaning the slope fractured and slid without a ski cut or explosive but as a patroller simply approached the starting zone. Also in the northern Madison Range, a snowboarder observed several natural avalanches breaking in the new snow/old snow interface 1-2 feet deep on steep, wind loaded slopes with a SE aspect. On similar slopes he easily triggered wind slabs with ski cuts and noted continued wind loading by generally west winds.
In the northern Gallatin Range on Mt. Ellis, Karl experienced minor collapsing. In stability tests he was surprised by the reactivity of facets about 8 inches deep despite minimal new snow in that area. Further south near Cooke City, a regular observer found a similar layer that was sensitive on some slopes and less on others. Today, with this layer present and strong winds overnight, human triggered avalanches are probable on slopes steeper than 35 degrees with wind-blown snow where the avalanche danger is CONSIDERABLE. All other slopes have a MODERATE avalanche danger.
YouTube: Saddle Peak Avalanche Q&A
The Saddle Peak Avalanche Q&A held March 4th at the Bozeman Public Library is now online thanks to the Randy and Kristin Wimberg. The entire 75 minute session can be viewed in two parts. Find it on our Videos Page or here: Part 1, Part 2.
Eric will issue the next advisory tomorrow morning at 7:30 a.m. If you get out in the backcountry let us know what you find. You can reach us at 587-6984 or email us at mtavalanche@gmail.com.