Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Sunday, March 29th, at 7:30 a.m. Island Park Adventures and Yamaha in cooperation with the Friends of the Avalanche Center sponsor today’s advisory. This advisory does not apply to operating ski areas.
Though raining in Bozeman this morning, snow was rapidly piling up in the mountains. Overnight 4-6 inches fell in mountains near Bozeman, 8-10 inches near Big Sky, and 12 inches near Cooke City and West Yellowstone. Temperatures were in the mid 20s F with winds blowing 10-25 mph from the southwest. This storm will bring cold air today and temperatures will slowly drop reaching the mid teens F by later this afternoon. Winds will stay strong at ridgetops and blow 20-30 mph from the west slowly shifting to the north. Make plans to call in sick to work because snowfall will continue with another 10-15 inches accumulating by tomorrow morning.
The Bridger, Gallatin and Madison Ranges, and the Lionhead area near West Yellowstone:
The forecast today is simple. Avalanche activity occurred throughout the advisory area before this storm. With heavy snow and strong winds, more avalanches will occur today. Winds blew from the southwest yesterday, and they will blow from the west today slowly shifting to the north, thus loading many aspects. This wind drifted snow will add significant stress to a layer of very weak, faceted snow found about 2 ft above the ground. Avalanches sliding on this layer will be large and destructive. Not all slopes have this weak layer, but many have an ice crust formed last weekend with a thin layer of small facets above and below it. Avalanches fracturing on this layer will be 2-3 ft deep. Lastly, slopes lacking any notable weak layer but containing recently formed wind slabs will also produce slides fracturing within the storm snow.
The avalanche danger is rising as snow falls and the wind blows. Today natural and human triggered avalanches are likely on wind loaded slopes where the avalanche danger is HIGH. Slopes without wind drifted snow have a CONSIDERABLE danger.
The mountains around Cooke City and the Washburn Range:
The mountains near Cooke City mostly lack the deeply buried weak layers found in the rest of the advisory area, but isolated pockets containing these layers do exist. Heavy snowfall combined with strong winds will stress the weak layer in these areas and a few deep slab avalanches are possible. On most slopes avalanches will occur within the storm snow especially on slopes with a wind load. Today natural and human triggered avalanches are likely on wind loaded slopes steeper than 35 degrees where the avalanche danger is HIGH. All other slopes have a CONSIDERABLE danger.
HYALITE CANYON REMINDER
If you were hoping to venture into Hyalite Canyon, this weekend is your last chance as the road will be closed from Wednesday, April 1st until May 15th for spring break up. For more information:
Doug will issue the next advisory tomorrow morning at 7:30 a.m. If you get out in the backcountry give us a call or send us an email with your observations. You can reach us at 587-6984 or at mtavalanche@gmail.com.