Dec 21, 2009 @ 12:00 am

December 21 Avalanche Advisory

West Central Montana Avalanche Center
Avalanche Advisory
Posted Monday December 21, 2009 at 0600

Good morning backcountry riders and sliders! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for the 2009 Winter Solstice on Monday December 21, 2009.

Current Avalanche Danger

The avalanche danger is HIGH above 7000′ on any terrain steeper than 35 degrees that has enough snow to cover anchors. The heavy, dense snow accumulating at the higher elevations is stressing extremely weak basal snow to the point of failure in many locations and on all aspects.

At lower elevations, 5000 to 7000 feet, and in areas where the snow has not yet buried anchors the avalanche danger is MODERATE.

It rained to 6500 feet Sunday with very little snow accumulation during the warm temperatures the past several days. At this mid-range elevation, the snow has either settled out or slid out where deep enough and will set up like concrete once cooler temperatures arrive later this week.

Below 5000 feet, the avalanche danger is LOW.

Weather and Snowpack Analysis

We still have a complex situation mostly at the higher elevations. Many high elevation locations throughout the advisory area do not yet have the depth required to cover anchors and in many cases, the travel getting there is difficult. Anyone that has been out on a sled or skis touring the past few days will verify how tough the off trail travel is under these conditions.

Mountain temperatures have been warm, into the 30’s since Thursday, and SNOTEL sites have only picked up .4 to about an inch of snow water equivalent since our last report. Most of the wet weather has been in the northern areas but temperatures have been consistent from SNOTEL to SNOTEL.

At the high elevations, there is 50cm of faceted snow at the ground now protected from these moderate temperatures so this weak snow is going to be with us for several weeks. We were experiencing collapse noises and fracture propagations and getting very low stability test scores while on a tour in the Rattlesnake Sunday.

This YouTube video shows why we are concerned about the future of our snowpack in the higher, steeper ground in the Bitterroots, Rattlesnake, Swan and Mission Mountain ranges.

It is all about timing, elevation, how much snow a particular location received and if a slab has formed above the faceted snow that formed in early December. Many places did not yet have a slab above these facets last week. Now there is.

Take a little extra time to gather as much information as possible and do not rely on one set of data that proves what you set out to do. I would not want to find myself on any steep open terrain these days. Pay attention to what you see and hear. The steep and deep is dangerous right now.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting a warm moist southwesterly flow with high snow levels. A cold front will push through the area Monday night causing a burst of heavier precipitation. A moist and unsettled pattern will persist through Wednesday.

Expect avalanche conditions to deteriorate if we receive heavy new snowfall. It’s going to take several weeks for the weakness at the base of the upper elevation snowpack to gain strength.

We will post the next avalanche advisory on Christmas day.

Transceiver Park Information

There are now 3 Beacon Basin avalanche transceiver parks in operation in western Montana. They are located at Lost Trail Powder Mountain, Lolo Pass Visitor Center and Montana Snowbowl. All three will be available for use for the entire season during operating hours at the ski areas and Lolo Pass Visitor Center.

The Beacon Basin at Montana Snowbowl requires purchase of a lift ticket to access the site located at the backcountry access point to Point Six and is available everyday. If the unit is not there, check in with the ski patrol in the Warming Hut at the top of the Lavelle lift and they will give you the control unit with directions to the site.

Easy, free and a fun way to practice using that fancy transceiver you have that will freak you out when you are in a real avalanche situation where your best friend is buried.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at [email protected] or call us at 406-530-9766. 406-530-9SNO.


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.