Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, March 22, at 7:30 a.m. Montana Import Group, in cooperation with the Friends of the Avalanche Center, sponsors today’s advisory. This advisory does not apply to operating ski areas.
Yesterday, winter officially ended with the Equinox. Saying good-bye to an old, reliable friend is difficult, but spring is full of energy and ready to play. It started snowing early this morning and at 6 a.m five to seven inches has fallen in the mountains. Temperatures are near 20F as winds average 15-25 mph from the west to southwest. Today will remain stormy and snowfall will taper off later this afternoon. Temperatures will reach the high 20s as winds remain moderate out of the southwest. An additional four to six inches should accumulate today.
The Bridger, Madison and Gallatin Ranges, the Lionhead area near West Yellowstone, the mountains around Cooke City and the Washburn Range:
The snow this morning is wet and dense. Even though this type of snow typically bonds well to the old surface, during a storm the snowpack is the most unstable as it adjusts to its new load. This storm is dropping snow fast, up to two inches an hour, which further stresses the snowpack. We do not need layers buried deeply to get avalanches—this new snow may sluff, break near ridgelines on wind drifts or be triggered on steep slopes.
In the last week we’ve seen and heard of a variety of instabilities, but these were all localized and not representative of a wider area. As the avalanche danger settles into a moderate or low danger it’s easy to get lazy and think that avalanches can never happen. But this is wishful thinking. There is always variability in the mountains and here’s a sampling from the last five days:
1. On Thursday, graupel under last week’s snow avalanched a skier in the Bridger Range (video).
2. Friday, Eric investigated a natural avalanche in the Bridger Range that fractured on facets that were born in November (video).
3. Also on Friday, much to our surprise, Mark and I found our stability tests propagating, on a lone southeast facing slope on Buck Ridge (video).
4. Over the weekend a skier found a thin, weak and unstable snowpack in the northern Gallatin Range right around the corner from a stable pack.
5. Another skier on Garnet Mountain found facets a few feet thick on the north face, a problem if this slope ever gets a meaty slab of snow on it.
In first aid classes they always teach us to Look, Listen and Feel to determine the state of a patient, which is pretty good advice for the snow too. Given this morning’s storm it’ll be possible to trigger avalanches today and I’m rating the avalanche danger MODERATE. Since we are in the middle of a storm the danger could rise further with more snow and wind.
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.