Good morning. This is Ian Hoyer with a spring weather and snowpack update on Monday, April 25th. The Gallatin National Forest Avalanche Center has stopped issuing daily avalanche forecasts for the season. We will issue our final weather and snowpack update of the season on Friday April 29th.
Between Thursday night and Sunday morning, a large spring storm left 1-2 ft of fresh snow across most of the advisory area (Lionhead only received a few inches). The storm system moved out yesterday, with skies clearing and temperatures rising above freezing. Today will be mostly sunny with mountain temperatures in the 40s and 50s F. Clouds will move in for most of the rest of the week, but there will also be sunny periods mixed in. High temperatures will be in the 40s F. There are chances for light precipitation starting on Wednesday, but it won’t amount to more than a few inches of snow.
All Regions
This weekend’s storm was one of the larger storms of the season. In Hyalite, it was the largest storm of the season (with 2.5” of snow water equivalent). With so much fresh snow, there were many avalanches, both human triggered and natural (see the avalanche log for a surely incomplete list). Avalanches were remotely triggered (details) and caught and carried skiers (details). The new snow has now had some time to stabilize, so it won’t be so wildly unstable today, but you could still trigger a slide. Watch for cracks shooting in front of you as signs that the new snow is unstable. The hazard will linger longest on shady, high elevation slopes where the snowpack stays the coolest. Digging down to test the interface between the new and old snow will let you know if you’ve found a slope where you could still trigger a slab avalanche.
The major hazard has now shifted to wet snow concerns. Strong late spring sun and temperatures well above freezing will quickly destabilize the new snow. With so much new snow, loose avalanches could pick up a lot of volume and be very dangerous. Plan to avoid steep sunny slopes as they warm up. Conditions will change rapidly, so if you see and feel the snow surface getting wet, don’t delay. Quickly move to lower angled terrain.
As it gets cloudier and a little cooler later in the week and further out from the big storm, the avalanche hazard will generally decrease. However, there may be a little bit of new snow, in which case, newly formed wind drifts will be a concern. If it does snow, watch out for those wind drifts, particularly in very steep, high consequence terrain.
This week’s weather will be classic Montana spring weather, with a little bit of everything - sun, clouds, warm temps, and maybe some rain or snow. This means you’ll need to be ready for anything. That means carrying rescue gear (beacon, shovel & probe), traveling with a partner, and watching for signs of instability is essential.
We will issue spring snowpack and weather updates each Monday and Friday through April and we will share relevant avalanche and snowpack information on our website and social media. If you get out, please send us your observations no matter how brief. You can submit them via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).
Announcements, Avalanche Education and Events
Bridger Bowl is closed, and backcountry conditions exist. There is no avalanche mitigation or ski patrol rescue. In case of emergency, call 911. Please stay clear of work areas, snowmobiles, chair lifts and other equipment. Without the daily avalanche mitigation efforts of the ski patrol, backcountry conditions now exist within the boundaries of Bridger Bowl (video). Commonly traveled routes such as the North Bowl Road and any slope steeper than 30 degrees are avalanche terrain (i.e. most of the Ridge and Schlasman’s terrain). Other groups above and below you may complicate principles of safe travel.
See our education calendar for an up-to-date list of all local classes.
Snow will be around the mountains for a month or two and avalanches will continue. When warm temperatures return, wet snow hazards will increase. If there are big spring snowstorms, dangerous conditions may develop for new snow avalanches and wind slabs. With either extended warming or a big storm, there is still a lingering possibility of deep avalanches breaking on weak, sugary snow near the ground. See this article for some general spring travel advice.