Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Saturday, February 16 at 7:30 a.m. A Montana FWP Recreation Trails Grant sponsors today’s advisory. This advisory does not apply to operating ski areas.
No snow fell since yesterday. This morning temperatures were mostly in the low 20s F. Winds were blowing 15 mph from the W with gusts of 25 mph. A short lived ridge of high pressure will bring another day of mostly sunny skies and warm temperatures. Temperatures will rise into the 30s F with no change in the winds. Clouds will return tonight. Snow will start falling early tomorrow morning and continue through the day.
Northern Gallatin Range
Since last Saturday, the northern Gallatin Range received more snow than most other areas. It also has widespread weak layers of facets buried 2-3 feet deep either near the ground or in the middle of the snowpack. I wouldn’t trust steep slopes in this area until at least a week passes without new snow or major wind events, even then I would be hesitant to venture into avalanche terrain without very careful snowpack evaluations. For today the avalanche danger is CONSIDERABLE.
Cooke City
The mountains around Cooke City simply have a lot of new snow which is the main avalanche problem. Fortunately this area mostly lacks persistent weak layers in the snowpack. The exception is areas with a thinner snowpack mostly at lower elevations or isolated slopes at higher elevations (video). Also watch for recently formed wind slabs or drifts. They will be less sensitive than they were yesterday but can still produce an avalanche. For today the avalanche danger is rated MODERATE.
Bridger Range Madison Range Southern Gallatin Range
Lionhead area near West Yellowstone
The situation is more complex in the Bridger Range and the mountains near Big Sky and West Yellowstone. In general facets can be found roughly 1.5-2 feet deep. Yesterday near West Yellowstone, Eric and his partner skied on mostly S facing terrain. They found unstable conditions (collapsing and cracking) below 8500 feet while at higher elevations the snowpack was generally deeper, stronger, and stable. In the northern Bridger Range yesterday, I found areas of concern to be dependent on where snowpack was thin in January (photo) based on wind patterns and terrain like steep rocky areas that takes longer to build a deep snowpack. Also, downhill winds were loading specific terrain features but not loading many others.
These faceted layers formed during cold weather in January in places that had a thin snowpack due to low elevation or wind scour. Higher elevation, but wind sheltered slopes may have also these facets. Many other high elevation areas did not form these faceted layers due to a deeper snowpack and/or a wind hardened snow surface. Finding stable slopes requires a keen eye and a few snowpits. Today, rating the avalanche danger is tough because it will be higher on some slopes and lower on others. Overall however, the avalanche danger today is MODERATE.
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.
Avalanche on Alex Lowe Peak in Hyalite – Read the accident report with a video, photos, and a snowpit; all posted here.