Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Thursday, March 7 at 7:30 a.m. Montana Ale Works in partnership with the Friends of the Avalanche Center sponsors today’s advisory. This advisory does not apply to operating ski areas.
Since yesterday the mountains near West Yellowstone received 8 inches of dense snow, the mountains near Cooke City and the Southern Madison Range received 5-6 inches, the Bridger Range received 4 inches of very dense snow, the mountains near Big Sky received 2-3 inches, and the Northern Gallatin Range received 1 inch. SW winds increased yesterday and were averaging 10-20 mph this morning with gusts of 35 mph. Temperatures were in the high teen F.
Today the northern half of the advisory area will see more sun than the southern half. Depending on the amount of sunshine high temperatures will climb into mid 20s to low 30s F and steady SW winds will continue. More snow will come tonight and deposit 2 inches of new snow at the southern end of the advisory area.
Bridger Range Southern Madison Range
Southern Gallatin Range Lionhead area near West Yellowstone
Cooke City
In most parts of the advisory area, snowfall since yesterday contained 0.5 – 0.8 inches of water. This snow arrived with strong SW winds which have transported the new snow. New snow + wind = fresh wind slabs. Skiers and riders can certainly trigger these fresh wind slabs today.
There is an additional concern: weak layers of faceted snow buried 2-3 feet deep. In some places like low elevations or steep rocky terrain at high elevations, the snowpack is less than 3 feet deep. In these places the facets are very weak and obvious in snowpits. A recent avalanche spotted yesterday in the Bridger Range on Sacajawea Peak occurred in a steep rocky area near the summit. In other places with a snowpack 4-5 feet deep or more, these facets are less obvious visually but can be found with stability tests (video). These faceted layers will be stressed by yesterday’s snowfall especially near West Yellowstone which got the most snow.
For today, with new snow, wind and lurking weak layers, the avalanche danger is rated CONSIDERABLE.
Northern Madison Range Northern Gallatin Range
The mountains south of Bozeman and near Big Sky only received 1-3 inches of new snow but SW winds have formed wind slabs which will be the main concern today. These areas also have layers of weak facets lurking in the snowpack. Skiers on Mt Blackmore yesterday spotted a recent avalanche on the east face. It broke about 35 feet wide and 2-3 feet deep in rocky terrain. Without much new snow, it will take the load of wind-blown snow to activate these facets today. For today, the avalanche danger is rated CONSIDERABLE on all wind loaded slopes. Non wind loaded slopes have a MODERATE avalanche danger.
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.
Montana Ale Works Fundraiser Dinner
Tickets are on sale now to the 5th Annual Friends of the Avalanche Center Dinner and Wine Pairing on Wednesday, March 13th at 6:00 p.m. Call the host stand at 587-7700 to reserve your space. Tickets are $75 and all proceeds go to the Friends of the Avalanche Center. There are only 40 tickets available and this event sells out every year so get them while you can!