Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Saturday, March 11th at 7:00 a.m. Today’s advisory is sponsored by Gallatin Valley Snowmobile Association and Montana Ale Works. This advisory does not apply to operating ski areas.
As snow tapered off yesterday morning the mountains near Big Sky and Cooke City got another 2-4” of dense snow. Yesterday, wind out of the west to southwest reached gusts of 40-50 mph. This morning, wind is west at 10-20 mph and temperatures are 20s to low 30s F. Under partly sunny skies today, wind will be westerly at 5-15 mph with temperatures reaching the mid-30s F. A round of snow showers tonight will drop 2-4” by tomorrow morning.
Wet Snow: Warm temperatures and sunshine today will moisten the snow surface and make wet loose avalanches likely on steep slopes. Avalanche danger could rise to CONSIDERABLE on all slopes by late morning. Avoid steep slopes if you see roller balls or can make snowballs with damp snow on the surface.
Cooke City
The mountains near Cooke City got 4-5 feet of snow totaling over 5” of snow water equivalent (SWE) in the last week. Eric rode north of town yesterday and found new snow bonded well on non-wind loaded slopes. He noticed natural avalanches on wind loaded slopes that were triggered by cornice falls (photo). Skiers in Sheep Creek saw a large natural avalanche that broke hundreds of feet wide, stepped down into older snow, and piled debris in flat terrain at the bottom (photo).
Strong to very strong wind over the last week grew cornices to massive sizes and formed thick drifts near ridgelines. These drifts are easy for a rider to trigger today, or could break naturally from a cornice fall. Avoid recently wind loaded slopes and give cornices space from above and below. Today, wind loaded slopes have a CONSIDERABLE avalanche danger and non-wind loaded slopes have a MODERATE danger.
Lionhead area near West Yellowstone
Madison Range Gallatin Range
The mountains south of Bozeman, near Big Sky and West Yellowstone got 2-3 feet of snow over the last week, and will get a reprieve from strong west to southwest wind today. Recent strong winds transported snow into fresh slabs and formed enormous, overhanging cornices along ridgelines. Yesterday I was in Beehive Basin and saw massive cornices that are ready to crumble (photo, video). Over the last week, three motorized groups near West Yellowstone had close calls when they triggered cornices from the ridgelines above. Two riders escaped separate incidents unharmed as their machines were sucked over the edge (video), and another group was happy to be far away when a large cornice collapsed nearby (photo).
Be extra cautious on slopes below cornices and stay far from the edge of ridgelines. When approaching ridgelines from the windward, scoured and non-loaded side, stay away from the opposite, leeward edge unless you are absolutely positive it is not overhanging cornice. Today, avalanche danger is CONSIDERABLE on wind loaded slopes and MODERATE on non-wind loaded slopes.
Bridger Range
The Bridger Range got 6-8” of snow Wednesday night, and avalanches are possible to trigger where moderate west winds drifted this snow into slabs. These slabs are most likely near ridgelines and possible on mid-slope convex terrain. Approach wind loaded slopes with caution and evaluate terrain for consequences of even a small slide.
Today, avalanches are possible on wind loaded slopes which have a MODERATE danger. Avalanche danger is LOW on non-wind loaded slopes.
I will issue the next advisory tomorrow morning by 7:30 a.m.
We rely on your field observations. Send us an email with simple weather and snowpack information along the lines of what you might share with your friends: How much new snow? Was the skiing/riding any good? Did you see any avalanches or signs of instability? Was snow blowing at the ridgelines? If you have snowpit or test data we'll take that too, but this core info is super helpful! Email us at mtavalanche@gmail.com or leave a message at 406-587-6984.
Beacon Training Park at Beall: Open and free to the public for avalanche beacon practice seven days a week from 9 a.m. to 8 p.m., southeast corner of Beall Park in Bozeman (photo).
COOKE CITY
Today! UYSC 21st Annual Hog Roast. More info here. Free avalanche rescue practice.