Jan 7, 2011 @ 7:01 am

January 7, 2011 Avalanche Advisory

Good Morning! This is Tim Laroche at the West Central Montana Avalanche Center with the backcountry avalanche advisory for Friday January 7th, 2011.

Current Avalanche Danger

On slopes steeper than 35 degrees on all aspects above 5000 feet the avalanche hazard is MODERATE. Natural avalanches are unlikely, human-triggered avalanches are possible. On all other terrain above and below 5000 feet, the avalanche hazard is LOW. Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Weather and Snowpack Analysis

We have received anywhere from 3-8 inches of new storm snow throughout our advisory area over the past few days. The Rattlesnakes, Northern Bitterrroots, and Swans have once again received the most precipitation. This snow came in wet and dense with a fair bit of wind out of the Southwest. Temperatures have been on the rise and the snow level was at ~5500 feet yesterday. Current temperatures are in the low 30’s at most SNOTEL locations.

The warmer weather we have been experiencing the last few days has allowed the snowpack to consolidate and strengthen in most areas. The new snow we have received has come in warm and has bonded well to the old snow surface. The added weight with warmer temperatures has helped to breakdown the buried surface hoar layers that we have been concerned with the past couple of weeks. Though these weak layers still exist, mostly on North through East aspects, it is getting more difficult to get them to fail in our stability tests(video).

While touring in the Central Bitterroots on Wednesday, we noticed that there is considerably less snow in the Southern and Central Bitterroots(South of the town of Lolo) than there is elsewhere in our advisory area. We found the snow to be well consolidated and very stable on all aspects. We tried to ski cut a 38 degree slope with no results. These conditions were different than one of our observers reported just North in the Bass Creek drainage. He reported small wet sloughs falling from areas of thin snowpack on steep slopes for most of the day on Thursday. He also captured a glimpse of a small natural slab that released from the rocks above the Bass Creek Falls(photo). These conditions were similar to the conditions that observers reported in the Lolo Pass, Lost Trail Pass, and Lookout Pass areas. Most of the stability test scores were in the upper moderate range.

In the Rattlesnakes on Thursday above 6000 feet, we found mostly stable conditions. Though we were able to get the buried surface hoar layer to react, it took a lot of force(ECTP24 and CT22) but did come off on a clean and planar shear(SQ1). So, the opportunity does exist to hit a sweet spot that could produce a sizable slide. Below 6000 feet the warm temperatures and liquid state of the precipitation was causing widespread wet point-release sluffs on all aspects. If we continue to get rain, expect this condition to continue on all slopes and aspects below the snow line.  This was similar to the observations we received from the Seeley Lake area.

Weather Forecast and Avalanche Outlook

Warming of the lower atmosphere will continue through the day today. This will keep snow levels fairly high through most of today. Cooler air will begin to move into the area this evening, starting from the North and moving Southward through the region Saturday morning. Once this cold front passes, the forecasts are calling for a light to moderate amount of snowfall to be accompanied by wind with the bulk of the precipitation falling on Saturday with snow levels back down to 1500 feet. By Sunday, we will see much colder temperatures and East winds as we are influenced by yet another arctic cold front.

I expect avalanche conditions to remain the same or deteriorate if we get more snow or rain, as it may be, than currently forecasted.

The next advisory will be issued Monday Janurary 10th, unless conditions change dramatically, then we will issue an update to this advisory.

The Kettlehouse Brewery is sponsoring Community Unite to benefit on January 12, 2011. This will be at their Northside location.

If you are out and about tonight for First Friday, La Parilla will be displaying  footage and still photography of Matt Kerns and Ian Magruder’s 2010 traverse of the Beartooth Mountains from Red Lodge to Livingston. ~5-10pm.


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.