February 22, 2013 Avalanche Advisory
The avalanche danger in the west central Montana backcountry is MODERATE. It may be possible to trigger an avalanche on exposed wind-loaded slopes steeper than 35 degrees above 6000 feet. Steep, loaded wind-pockets above 6000 feet are still harboring weaknesses in the snowpack. It has begun snowing in the mountains this morning and a robust winter storm is predicted. Expect the avalanche danger to rise to CONSIDERABLE by this afternoon.
Good Morning! This is Dudley Improta with the West Central Montana Avalanche Center’s avalanche advisory for Friday February 22, 2013.
Weather and Snowpack Analysis
Mountain temperatures are in the teens and low twenties. We are picking up snow in the mountains this morning across the region. The northern part of the advisory area is seeing up to 8 inches of snow with .6 inches of SWE (snow water equivalent) in the last 12 hours. Mountain winds are coming out of the south / southeast at 10-15mph and gusting to 20mph.
We had a report that snowmobilers triggered a couple of slides last Saturday in the Surveyor Lake area (between Hoodoo and Lolo Pass) on a southeast aspect. The avalanches involved new, wind-loaded snow. On Sunday, skiers in the Hoodoo Pass area turned away from an east aspect after getting some weak results in their snow pit. I spoke with one of the skiers; he indicated wind-loading was the issue. There was also a report of a skier remotely triggering an 8-10 inch slab on an east aspect near Lost Trail on Wednesday.
Last Tuesday Steve and I elected not to ski a steep rollover into a small couloir on a north/northeast aspect in the Rattlesnakes because it was obviously wind-loaded and I got a high energy shear with a compression test score of 14. We visited that same spot yesterday to further investigate the failure and recorded this video.
Tim and Dave traveled in the North Fork of the Jocko yesterday and reported generally stable conditions except for the possibility of wind-slabs on the higher exposed terrain. Reports from Lolo pass indicated generally stable conditions as well. Observers near Lookout Pass noted that the higher wind-loaded terrain was the main concern. Reports from Wisherd Ridge and the Southern Swans, the last few days, indicated generally stable conditions with wind-slabs, again, being the main concern.
There is weak surface snow, which is sluffing easily, on steep slopes from the Southern Missions (Southern Missions snow profile) to Lost Trail (Lost Trail snow profile). Not a problem right now, but could provide a weak interface for snow that is predicted for the weekend.
The Bottom Line
We’re hanging at MODERATE danger right now. The main avalanche problem is the exposed wind-loaded slopes at higher elevations. That being said, the Weather Service feels there is a storm approaching. If this storm materializes (read weather forecast below) the danger will ramp up to CONSIDERABLE. Weak surface snow was mentioned all over the region; something to keep in mind this weekend.
Weather Forecast and Avalanche Outlook
The Missoula Weather Service is predicting a significant weather system bringing possibly heavy snows into Western Montana. Strong southwest and west winds are expected to accompany this storm. West Central Montana may see up to a foot or more of new snow above 5000 feet. Snow banding (short periods of intense, local snowfall) are expected to develop Saturday evening. If this storm brings the snow and winds predicted the avalanche danger will elevate.
There is a Level 1 class in the Bitterroot beginning March 1.
There is an avalanche awareness class in Victor beginning March 6.
Tim will issue the next advisory on Tuesday, February 26.
Ski and ride safe and have a great weekend!