Good morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Forecast on Saturday, March 19th at 7:05 a.m. This information is sponsored by Cooke City Super 8/Bearclaw Bob’s and World Boards. This forecast does not apply to operating ski areas.
Yesterday morning a trace to an inch of snow fell near Big Sky and Cooke City. Temperatures reached 30-39 F yesterday, and this morning they are high 20s to low 30s F. Wind has been southwest to west at 5-20 mph with gusts of 25-35 mph. Today temperatures will reach high 30s to low 40s F under increasing clouds. Southwest wind will increase to 15-30 mph and snow is expected tonight and tomorrow ahead of a cold front. By tomorrow morning the mountains from Bozeman to West Yellowstone could get 2-3” with an inch near Cooke City, and by tomorrow afternoon another 3-5” are possible throughout the forecast area.
Today a person can trigger avalanches that break 1-3 feet deep. Over the last week we have seen that recent new and wind-drifted snow created an unstable slab over weak layers in the upper snowpack (Buck Ridge video). Yesterday near Cooke City, skiers and riders reported a couple recent large natural avalanches (photo and details, details), and a skier triggered avalanche that broke a foot deep (photo). All were large enough to bury or injure a person and examples of the type of slide that is possible today.
Throughout the forecast area weak layers are buried less than a couple feet deep, and you can easily dig down to see if they exist and create an unstable snowpack. Near Cooke City, there are additional weak layers buried around 3 feet deep that could cause larger slides. Avoid steep slopes where a stiff slab rests on top of sugary, weak snow or a hard crust, or worse, both weak snow and a hard crust. Avalanches breaking on these weak layers can be large and deadly, and can be triggered from flatter terrain below or adjacent to steep slopes (Wyoming Bowl video, Mt. Blackmore slide details).
Temperatures will rise above freezing in most areas today and make wet snow avalanches possible. Increasing southwest-west wind could blow snow into small fresh drifts that could break and avalanche under the weight of a person. Both of these types of avalanches will probably be small, but worth watching out for, especially in terrain where a small slide would be deadly if it pushed you over cliffs, rocks or into trees.
If you plan to ride, ski, climb or any sort of travel on steep slopes, carefully assess the snowpack for instabilities and evaluate terrain for the consequences of being caught in an avalanche. Today, large avalanches are possible to trigger, and the avalanche danger is MODERATE.
If you get out, please send us your observations no matter how brief. You can submit them via our website, email (firstname.lastname@example.org), phone (406-587-6984), or Instagram (#gnfacobs).
On Thursday, March 17th, there were two avalanche fatalities in the western United States. A snowboarder was caught, buried and killed near Ophir, Colorado (preliminary report) and two skiers were caught and buried, with one passing away on the west side of the Tetons in Wyoming (preliminary information).