Good morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Friday, March 18, at 7:00 AM. 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 near Bozeman, Big Sky, and the southern Madison Range got 2-3” of snow yesterday, and the rest of the area got a trace. Temperatures this morning are in the single digits F and wind is northerly at 5-15 mph. Today will be mostly sunny, temperatures will be in the teens to low 20s F, and wind will remain light out of the north-northwest. Expect warm temperatures and clear skies this weekend.
Southern Madison Range Southern Gallatin Range
Lionhead area near West Yellowstone Cooke City
The mountains in the southern half of our advisory area have weak layers of facets or surface hoar buried 2-4 feet deep. Today it will be possible to trigger avalanches on these weak layers. It will also be possible to trigger wind slabs that formed when strong westerly winds transported last week’s 2-3 feet of new snow.
Skiers near Cooke City yesterday observed natural activity from previous days on wind-loaded terrain (photo), and another group experienced large collapses that were failing on buried facets. Two days ago my partner and I found surface hoar buried 2 feet deep at Lionhead (video). Weak facets buried 1-3 feet deep are found near buried crusts on east and southerly aspects, and surface hoar 2-4 feet deep is found on shadier slopes. Dig to look for these weak layers, and avoid steep slopes if you experience collapsing, cracking, or avalanches. Wind-loaded slopes will be the most likely places to trigger an avalanche today. Avalanches are possible today and the avalanche danger is rated MODERATE.
Bridger Range Northern Madison Range Northern Gallatin Range
The mountains near Bozeman and Big Sky received 4-7” of low density snow since Wednesday. You may find small wind slabs on slopes leeward to northerly winds, but light winds last night were not enough to form large wind slabs. Due to rare north to east winds, these slabs will be on slopes that are not commonly wind-loaded.
It will also be possible to trigger wind slabs that formed from strong westerly winds earlier this week. On Tuesday, my partners and I were near Beehive and experienced wind-loading (video), and a skier in that area triggered two small wind slabs that day. These instabilities have had time to stabilize since winds calmed on Wednesday, but are still possible to find near ridgelines. Avalanches on buried weak layers are unlikely, so wind slabs are the main instability to watch out for today. The avalanche danger today is MODERATE on wind loaded slopes, and LOW elsewhere.
WET SNOW AVALANCHE DANGER
Cold temperatures will inhibit wet avalanche activity today, but March sunshine will warm the new snow on sunny slopes and make dry or wet loose avalanches possible. Expect wet snow avalanche danger to increase this weekend.
Eric will issue the next advisory tomorrow morning by 7:30 a.m. If you have any snowpack or avalanche observations to share, drop us a line at mtavalanche@gmail.com or leave a message at 587-6984.
EVENTS and AVALANCHE EDUCATION
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