Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Wednesday, February 18, at 7:30 a.m. Bozeman Audi in partnership with the Friends of the Avalanche Center sponsor today’s advisory. This advisory does not apply to operating ski areas.
Under partly cloudy skies temperatures are 10-15F in the south and 20F in the northern ranges. Winds are currently west at 20-30 mph with gusts of 40 last night in Hyalite. Today will be mostly sunny and warm with temperatures rising into the high 30s. Winds will increase later this afternoon and high clouds will filter in. Today and tomorrow will be spring-like, but “Winter” is scheduled to return from her vacation in Boston and show up to work first thing Friday morning.
Bridger Range Northern Madison Range Northern Gallatin Range Cooke City
Air temperatures will be warm today, but high clouds and wind will keep the wet snow avalanche danger at bay. Winds picked up out of the west with 40 mph gusts blowing last night. Wind-loaded slopes, mostly confined to higher elevation ridgelines, are the primary avalanche concern. These zones can be avoided since the smooth, chalky wind drifts are easy to spot. Under the wind-loads the snowpack is generally safe and stable (video, photo). A few isolated slopes harbor a thin weak layer of small facets making it worthwhile to do a quick stability test before committing to a line. On Monday, Eric found powder snow on Mt Blackmore and his video showed the potential for wind-loading. The mountains around Cooke City also have the same winds and snow available to transport. For today, the avalanche danger is rated MODERATE on wind-loaded slopes steeper than 35 degrees and LOW elsewhere.
Southern Madison Range Southern Gallatin Range Lionhead Area near West Yellowstone
West winds are blowing in the southern mountains and the few inches of new snow Monday morning is likely blown into drifts above tree line at the ridges. It will be possible to trigger these newly formed wind slabs today. Furthermore, the snowpack is tightly holding onto a weak layer of surface hoar 1-2 feet under the surface. This layer was laid down in January yet it’s still showing instability in our snowpits. It is not on every slope which means you have to dig down and search for it; not too onerous of a burden given how shallow it is. We have found the surface hoar in Taylor Fork, Teepee Basin and also Lionhead, where Mark made a video of this layer breaking in his stability test. For today, the avalanche danger is rated MODERATE on any slope steeper than 35 degrees, wind-loaded or not, and LOW elsewhere. My sense is that areas with a wind-load are not the same areas with surface hoar.
Mark 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 EDUCATION and EVENTS
Take a look at our Education Calendar for all classes being offered.
Companion Rescue Clinic, Bozeman, REI, 6-8 p.m., Friday, February 20 and 10 a.m.-2 p.m. on Saturday, February 21 (field location TBD). Pre-registration is required: www.rei.com/stores/bozeman.html
1-hour Avalanche Awareness, West Yellowstone, Holiday Inn, 7 p.m., Saturday, February 21.
Companion Rescue Course for Snowmobilers, Cottonwood Drainage, Crazy Mountains, Saturday, February 21, 9:30 a.m. – 2 p.m. Please RSVP to your club officers or to kathrynjbarker@fs.fed.us if you are interested in participating.
Snow Science and the Human Factor, Big Sky, location TBD, 6-8:00 p.m., Tuesday, February 24. The free event will feature a talk by Powder editor and MSU graduate John Stifter, multimedia presentations on the human factor in avalanche risk, a panel of experts from MSU’s Snow & Avalanche Lab and Gallatin National Forest Avalanche Center, as well as a Q & A session.