Good Morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Thursday, March 20 at 7:30 a.m. The Yellowstone Club Community Foundation, in partnership with the Friends of the Avalanche Center, sponsors today’s advisory. This advisory does not apply to operating ski areas.
This morning temperatures ranged from the high teens to mid 20s F. Winds were averaging 15-25 mph from the SW and gusting to 50 mph. A cold front will move over the area this morning and maintain strong winds. Areas near Bozeman should have the most clouds and may receive a trace of snow. Areas further south should have few clouds and no snow. The combination of cold air and some sun will means temperatures shouldn’t climb past the mid to high 20s F. Winds should stay strong through the day and shift to the W before easing tonight.
Bridger Range Gallatin Range Madison Range
Lionhead area near West Yellowstone Cooke City
Yesterday ski patrols at both Bridger and Big Sky found sensitive wind slabs formed by NW winds. Strong SW winds overnight may have formed new wind slabs in other locations this morning. Fresh wind slabs are not trivial and can easily bury a person. However, they are easy to see and avoid making them a simple avalanche problem.
Avalanches breaking deeper in the snowpack on buried facets are a more difficult problem. Most of these deep avalanches have broken on facets near the ground that formed in early December. Monday night’s storm favored the Hyalite area (almost 2” SWE) and Big Sky (over 1” of SWE) and these areas would be the most likely ones where you could to trigger a large avalanche. However, weak facets near the ground exist everywhere. Any slope with a relatively thin snowpack is suspect because the facets will be weaker. Also, thinner spots near rocks are good trigger points. These deep slab avalanches are a difficult problem in many ways (article and video on deep slabs).
When we consider going into avalanche terrain, the most important question to ask is “Has there been recent avalanche activity?” Unfortunately, we can’t seem to go more than a day or two without avalanches breaking somewhere in the advisory area. Two recent slides were spotted yesterday in the northern Bridger Range (photo1, photo2). On Sunday several slides were seen in Hyalite (photo). Most of the advisory area has the same weak layer near the ground; therefore, avalanches in one range are a good heads up for other mountain ranges. Observers are finding similar problems outside the advisory area as well (photo).
Today with fresh wind slabs near ridgetops, the avalanche danger is rated CONSIDERABLE on wind loaded slopes that are steeper than 35 degrees. A MODERATE danger exists on all other slopes.
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.
ACCIDENT REPORTS
10 March, Altoona Lakes Fatality (by West Central Montana Avalanche Center)
11 March, Crown Butte Fatality
15 March, Mount Abundance Injury
BLOG POSTS
Check out our latest Blog Posts. Mark wrote about the deep slab avalanche problem. Eric wrote an article about what it takes to put out an avalanche forecast and Doug recapped some lessons from the Beehive avalanche incident in February that was published in Carve.