Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Friday, March 22 at 7:30 a.m. Cooke City Motorsports and Yamaha in partnership with the Friends of the Avalanche Center sponsor today’s advisory. This advisory does not apply to operating ski areas.
Since yesterday morning, Hyalite Canyon received 4 inches of new snow. Most other places received 1-2 inches while the mountains near West Yellowstone got a trace at best. Temperatures this morning dropped into the single digits F and winds were blowing 10 mph gusting to 15 mph from the W. Yesterday winds blew 20 mph gusting to 40 mph from the W.
Weather for the next few days should be perfect for preserving snow quality: cold temperatures, light winds, and not too much strong sunshine. Today temperatures will struggle to reach the teens F and winds will shift to the N and blow 5-10 mph. About an inch of snow should fall this afternoon.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
The primary avalanche concern today will be wind slabs that formed yesterday from strong W winds. Ski patrollers at Bridger, Big Sky and Moonlight triggered many fresh wind slabs yesterday with explosives and ski cuts. Skiers on Saddle Peak triggered a wind slab near the summit 8-10 inches deep, 100 feet wide, and over 500 feet long. Another natural avalanche was seen near Cooke City (photo). The problem with recent avalanches isn’t so much their size but that they can easily sweep you into trees, into a gully, or over rocks and cliffs. Consider the runout zone of the slope were you will ski or ride.
There are always avalanche problems and bad news, but there is good news too:
- Light winds forecasted for the next few days should not drift more snow and allow yesterday’s wind slabs to stabilize.
- Snow over the last seven days has bonded well to the underlying snow and ice crusts.
- Deeper, faceted layers in the snowpack have not produced dry snow avalanches since early this month. Some wet slab avalanches occurred last week on these layers, but recent cold weather refroze the snowpack and eliminated this problem on many slopes.
Now is a great time to get out. Unless winds increase or more than a few inches of snow fall, the danger will be dropping relatively quickly and skiing/riding conditions are great. Today, avoid fresh wind slabs and assess bonding within the new snow. Conduct a few very quick stability tests and watch how the new snow reacts under your skis or your track on small, steep slopes. Deeper faceted layers are unlikely to produce avalanches except at the higher elevations in more “extreme” terrain. Eric was in McAtee Basin south of Big Sky yesterday and describes these problems in this video.
Although wind slabs will be less sensitive compared to yesterday, I’d still be nervous in very steep terrain with wind drifted snow. For this reason today, wind loaded slopes steeper than 35 degrees have a CONSIDERABLE avalanche danger. All other slopes have a MODERATE avalanche danger.
Note about danger ratings: The avalanche danger is an overall rating for entire mountain ranges and serves as a starting point in stability evaluations. As you travel, adjust the rating based on your observations. Today is a time when you might find many individual slopes where the danger is low. A good example was a recent observation sent from a regular observer and very experienced backcountry skier. He described the danger as ranging from low to high where he was skiing, not an uncommon situation.
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.