Jan 1, 2013 @ 6:10 am

New Year’s Day 2013 Avalanche Advisory

Avalanche Danger in the west central Montana backcountry is rated as MODERATE. On slopes that are 35 degrees and steeper, and are  7000 feet in elevation and above, it is possible to trigger avalanches. On other terrain in west central Montana the avalanche danger is rated as LOW. LOW avalanche danger does not mean “no avalanche danger”; isolated pockets of instability may exist on steep terrain.

Happy New Year! This Dudley Improta with the West Central Montana Avalanche Center’s advisory for January 1, 2013.

Weather and Snowpack Analysis

We experienced the “arctic fluff” we hear about in Utah. But, we got a few inches; not a couple of feet. The last few days it turned cold and the forecast area received an inch or two here, and an inch or two there, of very cold, light snow. That snowfall coupled with some surface faceting has led to some light fluffy stuff on top; 6 to 14 inches, depending on where you’re riding.

The cold temperatures, however, have allowed our wind-slab problem to persist. Friday, skiers triggered a wind-slab with a 12 to 14 inch crown on a steep north slope in the Rattlesnakes. While touring near Lost Trail Pass on Sunday one of our observers, Rich Raines, had some collapsing on a wind-slab and noted a recent localized slide on a very steep southeast slope. Yesterday, an observation from Wisherd Ridge near Missoula reported a very weak Rutschblock score (the block slid while being cut) involving the top 18 inches of the snowpack on an eastern aspect.

This tells you, while things are generally stable and folks are riding and skiing steep lines, we have potential avalanche problems in specific terrain features. The way to figure out if there is a problem is to take a bit of time, dig a snowpit and check things out. You may not be seeing or hearing the obvious clues (i.e. whoomphing, collapsing, recent activity) and a simple snow test might reveal a weakness in the snow.

A secondary problem is the cold surface snow is readily sluffing on steep slopes (35 degrees and steeper). Not a big problem if you have some sluff management skills; but if you are in terrain where a sizeable sluff could carry you into trees, rocks, or over a cliff it could be a bad situation. There are areas in the Rattlesnakes where the light snow is sitting on top of stiff, wind-hardened snow. In these places the new snow sluffs easily.

Weather Forecast and Avalanche Outlook

Drier air is expected to move in this evening as high pressure builds into the region. This will set the stage for surface hoar formation. This is not a problem now; but possibly could be a weakness in the snowpack when we get more snow. For now, milder air temperatures are predicted for the upper elevations. If these temperatures occur, it should settle the existing snowpack.

Video and Other Info

We posted this youtube yesterday:  My New Year’s resolution is to count correctly, my first failure is a CTM 18 (not 8) and my second failure is a CTH 22 (not 23). The point is, as I mentioned in the advisory, even though things look awesome, go through your protocols and have a look at the snow if you’re in steep terrain. You can see this area is wind-scoured with a shallow snowpack. New Year’s Eve 2012.

You can view current season snowpit profles here: 2012/2013 season snowpit profiles

If you’re out and see avalanche activity or have other observations, you can use our public observations form . If you would like to send us a note or  have an avalanche question you can use [email protected].

Have a fun & safe holiday!

I will issue the next advisory Friday, January 4, 2013.


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.