Good Morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Wednesday, March 17, at 7:30 a.m. Our friend Javaman, in cooperation with the Friends of the Avalanche Center, sponsors today's advisory. This advisory does not apply to operating ski areas.
By March standards, yesterday was hot with temperatures reaching the high 40s to 50 in the mountains. Last night they only dropped to the low thirties. Yesterday, westerly winds were light at 5-10 mph, but picked up to 10-20 mph last night. Today clouds will increase from partly cloudy this morning to mostly cloudy tonight. Mountain temperatures will warm into the mid 40s and winds will shift to the northwest. I do not expect any snowfall by tomorrow morning, but hopefully later Thursday we'll see some flurries.
The Bridger, Madison and Gallatin Ranges, the Lionhead area near West Yellowstone, the mountains around Cooke City and the Washburn Range:
Yesterday's high clouds and slight breeze kept the wet avalanche activity in check. A few inches at the snow surface got wet from the warmth, but there were no widespread slides. Since today is shaping up to be cloudy and breezy I do not anticipate any wet avalanches until our next day of hot, sunny weather-possibly this weekend.
Skiers on Mount Wilson in the northern Madison Range found evidence of wet avalanches in a south facing couloir. On cooler north facing shots they limited their turns to slopes less than 30 degrees since weak snow is still easily found 6-10 inches under the snow surface. Off ridgelines and other exposed terrain the new snow from Sunday was blown into slabs that broke under the weight of a skier. A party on the north face of Lone Peak released a slide on this layer which then stepped down to the weak facets on the ground (photo) and ran 1,200 feet. A solo skier in the northern Bridger Range triggered a shallow, four inch slab on these facets too (photo1, photo2, photo 3). We are finding this weak layer throughout our advisory area. It's not going away anytime soon and will likely continue to avalanche when we get more snow.
Deeper in the snowpack are two other layers of concern. The first is surface hoar buried 1½ to 2 feet under. The second are 2-4 mm facets at the ground. Both of these layers are present on many slopes, but their instability is not uniform. This inconsistency makes the decision to hit a particular slope more difficult. The avalanche on Lone Peak was big. There are other slopes with a similar recipe. An observer in Cooke City wrote that he is concerned with the same layering down there. What do you do? The easiest is to avoid steep, exposed lines. The snowpack has been tricky all season which lowers my overall confidence level. This is one of those years when the big lines don't get skied often or at all. But if you have a high risk threshold and are hungry for the goods, then at the very least you should dig to see if these layers are unstable. Just "going for it" is a crap shoot. Professional gamblers know that over time, the house always wins.
For today, throughout our advisory area, the avalanche danger remains MODERATE on all slopes since it's still possible to trigger slides.
New Beacon Park
The Friends of the Avalanche Center used a donation from Yellowstone Adventures to help purchase this avalanche beacon training park in West Yellowstone. You can search for pre-placed beacons switched on/off by a control panel. Look for it by the orange snow fence just south of the old airport (photo).
Mark will issue the next advisory tomorrow morning at 7:30 a.m. If you get out in the backcountry let us know what you find. You can reach us at 587-6984 or email us at mtavalanche@gmail.com.