Good morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Sunday, February 27, at 7:00 a.m. This information is sponsored by Yellowstone Club Community Foundation and Mystery Ranch. This forecast does not apply to operating ski areas.
This morning, there is no new snow, temperatures range from single digits to mid-20s F, and wind has been westerly at 15-25 mph with gusts of 25-40 mph. Today, temperatures will reach high 20s to low 30s F, and wind will be west-southwest at 10-20 mph with gusts of 25-30 mph. There’s a chance a few snowflakes will fall this afternoon near Big Sky and West Yellowstone. Tomorrow night a few inches of snow are possible throughout the forecast area.
Yesterday in the northern Bridgers three separate groups of skiers triggered slabs of wind-drifted snow that broke 8-18" deep and some were hundreds of feet wide. One person was caught, but unharmed (details and photos), and a handful of other slides were remote triggered and nobody was caught (details and photos, details and photos).
On Friday and yesterday, westerly winds increased and drifted recent snow into hard slabs over the sugary, weak snow that formed during previous cold, dry weather. Yesterday’s avalanches are a clear sign that an unstable snowpack exists on wind-loaded slopes. The weak layers that were buried by recently formed drifts are “persistent” which means they are slow to gain strength and can remain unstable for many days or weeks. This weak snow exists from Big Sky to West Yellowstone, and although the bulk of yesterday’s activity was centered on the Bridger Range, recent small slides near Big Sky, Mt. Blackmore and in Teppe Basin are signs that unstable snow can be found, and avalanches are possible where wind has drifted snow into slabs above the weak snow (Mt. Blackmore photo, Blaze Mtn. photo, Tepee Basin photo).
Today avalanches are possible to trigger on wind-loaded slopes. Before riding on steep slopes, carefully assess the potential for wind-loading and buried weak layers. On slopes without recent drifts of snow, avalanches are unlikely. Avalanche danger is MODERATE on wind-loaded slopes and LOW on non-windloaded slopes.
A weak layer of snow buried 2 feet deep makes it possible for a person to trigger a large avalanche. Avalanches breaking on this weak layer become less likely to trigger each day without snow, but the consequences of being caught are potentially deadly. Examples of the type of avalanches you could trigger are two snowmobiler triggered avalanches last weekend, one of which was fatal (Miller Mountain fatality video). Two days ago I found unstable test results adjacent to one of these slides (Mt. Abundance video, details) which shows conditions still exist to trigger a large avalanche. Before you travel on steep slopes, carefully assess the snowpack for potential instabilities and consider the consequences of being caught in a slide. Large avalanches are possible and the avalanche danger is MODERATE.
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).
Upcoming Education Opportunities
See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming events.
March 4, Companion Rescue Clinic with the Bozeman Splitfest. Information and registration HERE.
Every Saturday near Cooke City, 10 a.m.-3 p.m. FREE snowpack update and transceiver/rescue training. Stop by for 20 minutes or more at the Round Lake Warming Hut.
A detailed report on last Saturday’s avalanche that killed a snow biker outside Cooke City is posted online. The video describing the avalanche can be viewed here.