Dec 31, 2010 @ 6:15 am

New Year’s Eve Avalanche Advisory, 2010

Good morning, this is Dudley Improta with the West Central Montana Avalanche Center’s avalanche advisory for New Year’s Eve, 2010.
Current Avalanche Danger
On all slopes above 5000 feet and steeper than 30 degrees there is a HIGH avalanche hazard. We are continuing the avalanche warning Steve issued on Dec. 30, 2010. On wind-loaded pockets and slopes below 5000 feet and steeper than 30 degrees there is a MODERATE avalanche hazard. Although rare, we have had avalanche accidents when gullies and pockets were filled with wind slabs on steep, low elevation terrain.

Weather and Snowpack Analysis

The area has received a lot of snow in the last 48 hours. Up to 2 feet of new snow fell in the Rattlesnakes with over a foot or more across the region. The storm came in with strong winds from the Southwest and then transitioned to more Northeast gusts Wednesday night. These variable winds loaded many aspects. Yesterday we traveled in the Rattlesnakes to an avalanche site that two skiers had triggered on Wednesday. The skiers lost some equipment but were able to return under their own power to the Snow Bowl Ski Area late Wednesday evening . On our tour we felt and heard collapse noises, observed cornice fall and natural releases on Northeast, Southwest and East aspects. The skier-triggered avalanche (and the video) was on a Northeast slope at 7500’ in elevation. The avalanche released on a 38 degree rollover. The recorded temperature at the time of the video was -6 F with 12mph winds. Observers from Lookout Pass, the Northern Bitterroots and the Lolo Pass area noted collapse noises, wind loading and unstable stability test results. The Snow Bowl ski patrol had the new load of snow move readily on West/Southwest facing couloirs with their Thursday morning bomb run. Observers from the Stateline near Lost Trail Pass reported a more stable snowpack with lighter density new snow. However, they cautioned about this new snow moving easily with the wind. A significant new snow load, high winds, collapse noises, natural and human – triggered avalanching; all the signs of avalanche hazard are present. One of our observers, Adam Clark (an experienced mountaineer) who was in Crystal Theatre near Lolo Pass, put it this way: “…all the new snow, whoomphing and a few shooting cracks kept me on low-angled and treed terrain…”.


Weather Forecast and Avalanche Outlook

Arctic air will become established across the region. Subzero temperatures will be commonplace across the Western Montana Ranges. The cold air will remain in place through Sunday. Westerly flow with light snows should follow. I would expect the avalanche conditions to remain the same with the bitterly cold temperatures expected for the next couple of days. Yesterday we experienced a -23F wind chill; today is colder. Happy brrrr New  brrrr Year. Stay safe. If you didn’t fill your loved one’s stockings with hand warmers – you blew it.

The next advisory will be posted January 3, 2011.

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.

For education opportunities including workshops, Level 1 and Level 2 classes please check our education and events page.

The Kettlehouse Brewery is hosting community night benefiting on Jan. 12, 2011.


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.