Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Thursday, March 5, at 7:30 a.m. This advisory is sponsored by a Montana FWP Recreation Trails Grant. This advisory does not apply to operating ski areas.
The only notable change in the weather is that winds increased overnight mostly near Bozeman and Big Sky blowing 20-40 mph from the W with temperatures in the teens F. Further south temperatures were in the single digits F, and winds were blowing 5-15 mph from the W. A ridge of high pressure over the area today will bring sunny skies and temperatures warming into the upper 20s and low 30s F with strong winds continuing from the W.
Bridger Range Madison Range Gallatin Range
Lionhead Area near West Yellowstone Cooke City
Winds increased overnight and today the main problem to watch for will be recently formed wind slabs. In some places these wind slabs may be resting on a layer of small, weak snow crystals (near-surface facets). A snowboarder triggered a sizable wind slab yesterday near Big Sky (photo) but was not caught. It was reported to be 8-10 inches deep and about 200 yards wide. Breaking over such a wide area indicates that it may have fractured on a weak layer of facets.
Doug found this weak layer near West Yellowstone on Tuesday (video), Karl found it in the southern Madison Range, and USFS and USGS personnel found it near Cooke City in between several ice crusts (photo). An avalanche forecaster from Colorado found some thin wind slabs on NE aspects south of Cooke City resting on this weak layer. Doug skied on the west and east sides of the Bridger Range near Bridger Bowl and did not find these small facets near the snow surface but he did spot a few very small wind slabs that released naturally.
There are no weak layers lurking deeper in the snowpack, and you can avoid avalanches by simply avoiding fresh wind slabs. Because these wind slabs may be sitting on facets, they may remain easy trigger through the weekend. For today, the avalanche danger is MODERATE on wind loaded slopes steeper than 35 degrees. All other slopes have a LOW danger.
The Snow Science Program at MSU needs your Help!
They are looking for backcountry skiers and sledders to help them with a study on Human Factors. Watch this 2:46 minute video for details.
Forum on Snow Science and the Human Factor on video.
In case you missed it, here's the entire 1:13 hour video from the forum on Snow Science and the Human Factor at MSU. John Stifter, editor of Powder Magazine, talks about his own personal experience with the avalanche that killed three of his friends in 2012 at Tunnel Creek. Doug Chabot gives a presentation about Sidecountry Skiing and Digging Pits starting 44 minutes into the program.
I 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.
1-hour Avalanche Awareness, Bozeman, REI, 6:30 - 8 p.m., Wednesday, March 11.