Good Morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, March 30, at 7:30 a.m. Moonlight Basin Ski Patrol, in cooperation with the Friends of the Avalanche Center, sponsors today's advisory. This advisory does not apply to operating ski areas.
A strong, wet, unstable Pacific storm has already dropped 10-12 inches of snow in the southern mountains. The Big Sky area to the Bridger Range just started to get hit and has one to two inches of snow at 6 a.m. West to southwest winds ripped across all elevations yesterday with speeds averaging 20-30 with gusts reaching the 60s. Winds will decrease today, but still blow 20-25 mph. By tomorrow morning snowfall will measure 8-12 inches in the north with possibly 16 inches in the south.
The Bridger, northern Gallatin and northern Madison Ranges:
The last few days have been windy. In the northern mountains these winds stripped south facing slopes of any loose snow, creating drifts on more northerly aspects. On Sunday, skiers on Mt. Blackmore up Hyalite abandoned their plans to ski the north face. Natural slides broke 1 to 1.5 feet deep on a layer of small facets that formed a few weeks ago. This layer will be our primary avalanche concern with today's snowfall. It's found throughout southwest Montana will get more unstable as the day progresses.
The faceted snow on the ground underlying the entire winter's snowpack should not be forgotten either. On Friday, a natural avalanche occurred on Cedar Mountain which broke on this deep layer. Like a neglected soul waving their arms wildly for attention, we can't ignore it. With new snow falling today, and wind speeds strong enough to blow this around into drifts, I expect the avalanche potential will rise. With only a couple inches falling by 6 a.m. the avalanche danger remains MODERATE on all slopes. But if the storm continues as planned, I expect the danger will rise to CONSIDERABLE.
The southern Gallatin and southern Madison Ranges, the Lionhead area near West Yellowstone, the mountains around Cooke City and the Washburn Range:
This is the largest storm of the winter in the southern mountains. Carrot Basin, West Yellowstone and Cooke City have already gotten 10-12 inches (1.4 inches of Snow Water Equivalency) with more on the way. Winds have been ripping here too with the anemometer on Lulu Pass showing steady 30-60 mph winds. Today visibility will be nil, snow will be falling sideways and travel in the backcountry will be burly. This new snow will continue to add stress to an already weak snowpack. A layer of small grained facets two feet under the surface will likely avalanche naturally on many slopes today. And near the ground, especially in the southern Madison and Lionhead area, the depth hoar from December will be quivering under this big load. The snowpack in the south has been on spring break for over six weeks: lots of rest and relaxation. Today is game time and the pack will suffer like a pudgy teenager entering boot camp. Given the weak layers becoming more unstable with every inch of snow added, the avalanche danger today is rated HIGH on all wind-loaded slopes. Slopes not affected by the wind will have a CONSIDERABLE danger.
Avalanche Fatality near Missoula
On Saturday March 27, a 29 year snowmobiler from St Maries, Idaho died in an avalanche accident near Missoula Lake on the Superior Ranger District of the Lolo National Forest. This area is on the MT/ID border 10 air miles SW from Superior, MT. For more information, check out the Advisories page on the West Central Montana Avalanche Center website.
I 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.