Posted:
Feb 10, 2012 @ 6:05 am

February 10, 2012 Avalanche Advisory

The avalanche danger in the West Central Montana backcountry is LOW.  Low avalanche danger does not mean there is no avalanche danger. No doubt, you could find isolated pockets with Moderate avalanche danger in terrain above 7000 feet that is wind-loaded and very steep (35 degrees +).

Good morning, this is Dudley Improta with the West Central Montana Avalanche Center’s avalanche advisory for February 10, 2012.

Weather and Snowpack Analysis

We’ve had some absolutely gorgeous weather for the last week. Lots of riders and skiers in West Central Montana made the most of the generally stable conditions and unlimited visibility.

Steve talked about surface hoar forming from the dry, high pressure weather in his advisory Monday. We thought perhaps wind and sun might have destroyed some of the surface hoar formation on some slopes. Tim and I went sledding yesterday near Lolo Pass and found the surface hoar alive and well on northerly, protected slopes. Observers near Lookout, Hoodoo and Lost Trail Passes noted very similar conditions. The crystals are impressive, and are now officially, buried surface hoar (bsh) because they are protected in much of the advisory area by the inch or two of snow that fell Wednesday night. Tim shows in this video how a small amount of snow can preserve these fragile crystals.  This photo also shows the surface hoar protected by an inch of snow. Observer, Rich Raines, sent in this photo of the surface hoar near Lost Trail Pass.

Snotels around the region show that the overall snowpack settled  6 to 8  inches over the last week. This is a strong sign of stability. The weak snow on the surface is not a problem now. It is snowing a bit this morning in the mountains; stay tuned as we get a little more snow on the existing weak surface.

Weather Forecast and Avalanche Outlook

The Weather Service is predicting light to moderate accumulating snows in the mountains for the next couple of days. The nature of the precipitation will be scattered showers with local accumulations. There is a winter weather advisory until  11am this morning. I would expect the surface of the snowpack to become less stable with this modest load. An inch or two here, three inches there, and pretty soon you have a small slab sitting on a notoriously persistent weak layer.

I will be at Lost Trail with a Level 1 class this weekend so Steve will issue Monday’s advisory, February 13. Thanks to the Ravalli County Search and Rescue, the Lost Trail Ski Area and the Lost Trail Ski Patrol for assistance with this class.

Have a great weekend. Ski and ride safe!

Snowmobile Education

We have Scott Schmidt with the Friends of the Gallatin Nat’l Forest Avalanche Center, accomplished rider and former avalanche forecaster, coming in to do a Level 1 avalanche class for sledders. We need a couple of more folks for the class to go. Check http://mslaavalanche2.wpengine.com/events/level-1-avalanche-class-for-snowmobilers/ for registration information.

If you get out and see avalanche activity or want to send us quick snow observations please use our public observations form on the home page missoulaavalanche.org or write us at [email protected] with any observations or questions.

READ FULL ADVISORY  

This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but the information can help you make a more informed decision regarding travel in avalanche terrain for the next few days.

Our advisory area includes National Forest System lands in the Bitterroot Mountains from Lost Trail Pass north to Granite Pass, the Rattlesnake Mountains north of Missoula and the Southern Swan and Mission Mountains near Seeley Lake, MT. Avalanche information for the Lookout Pass/St. Regis Basin area is available from the Idaho Panhandle Avalanche Center.