Jan 14, 2011 @ 6:36 am

Avalanche Warning January 14, 2011

Good morning! This is Dudley Improta with the West Central Montana Avalanche Center’s avalanche advisory for January 14, 2011.

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 yesterday.  On steep slopes below 5000 feet that are wind-loaded, loaded with heavy wet snow or rain-saturated there is a MODERATE avalanche hazard.

Weather and Snowpack Analysis

The last couple of days is all the reminder you need that the thirteen western counties in Montana are geographically part of the Pacific Northwest and our weather and snowpack can have a significant maritime influence.

Heavy, wet snow fell in the forecast area; from 9 inches around Lookout, Lost Trail and the Rattlesnakes to over a foot in the Lolo Pass area. The new snow contained up 1.5 to 2 inches of snow water equivalent. We are always concerned when the snow contains so much water (in this case up to 22% water) because it adds a tremendous amount of weight to the snowpack in a very short time.

The snow fell on very cold snow from the beginning of the week and has not had time to bond on that cold layer. Pit tests and observations from Lolo, Lost Trail and Lookout indicate an unstable situation. 

In addition we have significant wind-loading from the South / Southwest prior to and during the storm; so the North / Northwest aspects are particularly suspect. That being said, Steve and I were traveling from a snowpit on a South aspect to a Northeast aspect yesterday near Lolo Pass and we initiated a heart-stopping collapse on a shallow Southeast aspect. This video shows our East/Northeast pit near Lolo Pass.

Although weather stations indicate the loading in the Rattlesnakes; Tim’s field observations indicate the situation may be more stable. Reports and remote weather stations indicate the situation may be more stable in the Seeley Lake area as well;  but we encourage elevated caution where any wind-loading has occurred or new wet snow has accumulated.

On the bright side this is the kind of snow that settles quickly in a day or two.

Weather Forecast and Avalanche Outlook

Another surge of moisture will make its way into the region this afternoon with moderate snowfall in the mountains. This will be another maritime influenced event.  Any significant amounts of dense, wet snow (more than 3 or 4 inches) and/or rain will continue to make the snowpack unstable. 

Eventually the warmer temperatures will help stabilize things in the long run. 

Steve will issue the next advisory on Martin Luther King Day, 2011.

I will be giving an avalanche awareness talk for the Bitterroot Ridge Runners meeting on January 19.

Thanks to those who attended the Community Unite at the Kettlehouse that benefited Missoulaavalanche. Word on the street is you broke a “pints sold” record.


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.