Good morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Saturday, December 15 at 7:30 a.m. Today’s advisory is sponsored by Grizzly Outfitters and 406 Brewery in partnership with the Friends of the Avalanche Center.
Over the past 24 hours 1-3 inches of low density fell in most mountain locations with the exception of the northern Madison Range which picked up 4 inches. Currently, temperatures are in the mid to high teens F and winds are light, blowing 5-10 mph out of the WSW. Today, temperatures will warm into the low 20s F under partly cloudy skies and winds will continue to blow 5-10 mph out of the WSW. There is a slight chance of snow showers in the southern Mountains, but today should remain mostly dry. Another storm is forecasted to impact our area Sunday night into Monday.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
It's not even officially winter, yet - but it sure feels like it. After two weeks of near continuous snowfall, the snowpack in southwest Montana is well above average (NRCS Snow Update). In terms of snowpack stability, a deeper pack typically means a stronger pack. This has proven generally true so far.
Although our snowpack is looking good, it's not perfect. Today, the primary avalanche concern will be new snow instabilities. Avalanches failing on storm interfaces in the top 1-2 feet of the snowpack remain possible. On Thursday, a skier in the Bridger Range triggered a slab avalanche on Saddle Peak that failed within the storm snow. Fortunately, the skier was not caught. Also, Doug got unstable results on a storm interface at Bacon Rind on Wednesday (video) and Snowmobilers got similar results during stability tests in Teepee Basin in the southern Madison Range Yesterday (video, photo). Although our snowpack data is limited from Cooke City, I expect these types of instabilities to exist in that area as well.
This type of avalanche problem typically doesn’t live long but remains a concern as long as there’s new snow. Avoiding slopes steeper than 35 degrees, especially slopes that have been wind affected is the best way to mitigate this problem. Fortunately, winds have been relatively calm the past few days keeping transport to a minimum.
A less likely, but potentially more dangerous situation are avalanches failing on deeper layers in the snowpack. Large, natural avalanches in the northern Bridger Range earlier in the week are a prime example of this problem. Yesterday, Mark and I investigated one of these slides in Hollywood Bowl south of Frazier Basin. This avalanche failed on a thin layer of facets 1-2 feet above the ground and likely occurred during a rapid loading event this past Wednesday (video).
Buried facets are not widespread throughout our forecast area, but continue to make their presence known (see Doug’s video of Bacon Rind). Triggering a slide on a deeper layer will be most likely in steep, rocky terrain where the snowpack is thinner (photo). Carefully evaluating snow stability and terrain is a wise idea before committing to steep slopes.
Today, heightened avalanche conditions exist and human triggered avalanches are possible. For this reason the avalanche danger is rated MODERATE
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.
NEW TO THE AREA?
Check out our Place Names Map which shows common names of popular backcountry areas.
Snowmobiler Introduction to Avalanches with Field Course in West Yellowstone on December 20 and 21. Sign up for this class HERE.
Free 1-hour Avalanche Awareness lecture at Bridger Bowl at 1 p.m. in the Jim Bridger Lodge on Sunday December 23.