Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Sunday, March 12th at 6:45 a.m. Today’s advisory is sponsored by Grizzly Outfitters in partnership with The Friends of the Avalanche Center. This advisory does not apply to operating ski areas.
The mountains got 1” of snow overnight with 3” near Cooke City. This morning, wind is westerly at 15-25 mph with gusts of 40-50 mph and temperatures in the 20s F. Today, under mostly cloudy skies wind will be west to northwest at 25-35 mph with temperatures in the high 20s to low 30s F. Light snowfall tonight will accumulate a trace to 2” by morning.
Cooke City Lionhead area near West Yellowstone
Madison Range Southern Gallatin Range
Near Cooke City, West Yellowstone, and Big Sky heavy snowfall and strong wind over the last week create our main avalanche concerns today. The mountains near Cooke City got 4-5 feet of snow, and 2-3 feet of snow fell near West Yellowstone and Big Sky since last Sunday. Good news is there are no widespread weak layers to avoid and soft snow is found on slopes sheltered from sun and wind. On the flipside, overhanging cornices are ready to crumble and west to southwest wind formed thick slabs below ridgelines and on convex terrain.
Eric was in Cooke City on Friday and saw natural avalanches on wind loaded slopes (photo). Other skiers near Cooke City also saw multiple natural avalanches in wind loaded terrain (photo, photo, photo). Over the last week, three groups near West Yellowstone had close calls when they triggered cornices from the ridgelines above (photo). Two riders escaped separate incidents unharmed as their machines were sucked over the edge (video). I toured in Beehive on Friday where we avoided massive, overhanging cornices and triggered a small wind slab (photo, video). Yesterday, a large natural avalanche was observed on Fan Mountain near Big Sky (photo, photo).
Wind took a breather yesterday, but returned in full force last night. Snow from the last week continues to drift into wind slabs and grow cornices that are easy to trigger. Be extra cautious on slopes below cornices and stay far from the edge of ridgelines. When approaching ridgelines from the scoured and non-loaded (windward) side, stay away from the opposite (leeward) edge unless you are absolutely sure it is not overhanging cornice. Avalanche danger today is CONSIDERABLE on wind loaded slopes and MODERATE on non-wind loaded slopes.
Bridger Range Northern Gallatin Range
The mountains near Bozeman got around a foot of snow over the last week. Westerly wind drifted snow into slabs below ridgelines that are possible to trigger today. Cornices are mature and large this time of year and should be avoided or approached with extra caution.
There are no particular widespread weak layers to avoid, but always dig to check below your feet before committing to steep terrain. Last weekend I was surprised by an isolated, and not insignificant, instability on the west side of the Bridger Range (video). Be aware of increased uncertainty in unfamiliar and complex terrain. Practice safe travel and snowpack assessment regardless of lower danger.
Today, avalanche danger is MODERATE on wind loaded slopes and 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).