Good morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Sunday, March 17th at 7:15 a.m. Today’s forecast is sponsored by Basecamp Gallatin and Yamaha and Alpine Yamaha in Livingston. This forecast does not apply to operating ski areas.
There is no new snow. Temperatures are 20s to low 30s F. Wind has been out of the east to north at 5-10 mph with gusts of 15-35 mph. Today will be mostly sunny with temperatures reaching high 30s to mid-40s F and wind out of the northeast-northwest at 5-10 mph. The next couple days look similar, possibly warmer, before a chance for snowier weather after Wednesday.
Over the last couple days large avalanches were triggered, breaking deep on persistent weak layers. Yesterday in Taylor Fork a rider triggered a 2-4 foot deep slide on a short slope, he was able to grab a tree and escape the slide while it carried his snowmobile (photo and details). On Friday, outside but near our forecast area, a skier triggered a big avalanche from far away as they ascended a ridgeline (details and photos). This weekend we have seen less frequent avalanches than the previous couple weeks and months (avalanche/weather log), but the high consequences of these slides and difficulty assessing their potential on any given slope creates dangerous avalanche conditions (some notable recent activity: Blackmore video, Beehive video, Beehive photos, Cooke City activity list).
Above freezing temperatures during the day will increase the likelihood for wet snow avalanches. Smaller loose wet avalanches are likely and could trigger larger slides breaking deeper and wider. As the snow surface melts the addition of water and changes to the slab may make it easier to trigger larger avalanches. Plan to avoid steep slopes, and be extra cautious traveling below sunny slopes as they warm up through the day. Avalanche danger is CONSIDERABLE.
In the Bridger Range, and near West Yellowstone and Island Park, the likelihood is lower for triggering a large slide, but it is possible. A deeper snowpack in the southwest part of our forecast area is making it more difficult to trigger deep slides, and in the Bridger Range there has been less snow overall. Yesterday I was in the Bridger Range and saw weak snow near the ground in a four foot deep snowpit (observation), similar to what another group of skiers found (observation). We also saw natural wet loose avalanches on sunny, steep rocky slopes (photo).
It is reasonable to travel in some avalanche terrain, but it requires careful snowpack and terrain evaluation. Choose slopes that have clean runouts, with minimal consequences like trees or cliffs, in case you get surprised. Anticipate snow stability to decrease on sunny slopes as the snow heats up and gets wet through the day (video). Plan to be off of and out from underneath steep sunny slopes before the snow surface gets wet more than a few inches deep. Natural rollerballs or wet loose slides are your last warning sign to be off sunny slopes. Also, be on the lookout for small wind slabs formed by recent winds drifting the snow that fell earlier in the week. Human-triggered avalanches are possible and the avalanche danger is rated MODERATE.
If you venture out, please fill an observation form. It does not need to be technical. Did you see any avalanches? How much snow is on the ground? Was the wind moving snow? Simple observations are incredibly valuable. You can also contact us via email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).
Upcoming Avalanche Education and Events
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.
Loss in the Outdoors is a support group for those affected by loss and grief related to outdoor pursuits. Check out the link for more information.
On Tuesday, a backcountry skier was caught and killed by an avalanche near Lost Trail Pass. Preliminary information is available here.