Jan 27, 2012 @ 6:28 am

January 27, 2012 Avalanche Advisory

Above 6000 feet on wind-loaded terrain steeper than 35 degrees there is CONSIDERABLE AVALANCHE DANGER in the west central Montana backcountry. Careful snowpack evaluation, cautious route-finding and conservative decision making essential. On all other terrain above and below 6000 feet steeper than 35 degrees there is MODERATE AVALANCHE DANGER.

Good Morning! This is Tim Laroche at the West Central Montana Avalanche Center with your backcountry avalanche advisory for Friday, January 27th, 2012.

Weather and Snowpack Analysis

Most advisory area locations picked up 6-14 inches of high density snow (1.5-2.4”SWE)over the past couple of days. The winds blew hard in the 30’s gusting to 60 mostly out of the West and Southwest during the past 2 days. Winds have turned to the Northwest and are now only blowing 2-4mph with some lingering snow showers. Mountain temperatures are in the high teens in most advisory area locations.

The strong winds that accompanied our latest storm formed wind slabs on leeward aspects and terrain features that are sitting on a cold snow interface from Monday nights cold temperatures. These wind drifts are up to 2 feet deep in places and are failing easily in stability tests. These drifts should settle out quickly, but in the meantime conservative decision making is the name of the game. Pay particular attention to convex rollovers and steep open slopes where the slab can release above you. The Snowbowl ski patrol got 12” wind slabs to run easily during avalanche control work on Thursday.

The other concern in our snowpack is the buried persistent weak layers now down 60-80cm with a hard slab resting above. Most stability tests are not getting this layer to react, but when it does, it comes off clean and with a lot of energy. It is difficult to rely on stability tests for a deep hard slab instability, which is why conservative decision making is essential. We got a great report from Downing Mountain Lodge in the Bitterroot…John wrote ”No settling, no obvious signs of instability, no naturals observed but obvious high consequence cycle”.

There is a lot of variability in our snowpack throughout our advisory area this season. We have been finding good stability in some areas and weak stability in others with no real consistencies. Take the time to look for stability weaknesses on the slopes you plan to ski and ride on before committing to a steep open slope.


Weather Forecast and Avalanche Outlook

Northwesterly flow will be present over the Northern Rockies for the next couple of days with light snow showers possible over the mountains. The winds will increase again on Saturday night through Sunday ahead of the next Pacific storm system. Mountain daytime temperatures will be in the mid twenties until Sunday when temperatures will warm into the 30’s with the coming of our next good shot at moisture.

I expect the avalanche danger to decrease once the new storm snow settles out over the next couple of days.

I will issue the next advisory on Monday, January 30th.

Thank you to all of you that have taken the time to send us your observations. The information you send is very helpful. If you get out and have the time to send us some information about what you are seeing, please use our “submit observation” link on our website or send us a quick note at [email protected]. This information is invaluable to us and in turn comes back to you in the form of a better forecast.

Make your plans now to enjoy Warren Miller’s latest film “Like There’s No Tomorrow” on Friday February 3rd at the Wilma. Proceeds help to support the Missoula Avalanche Foundation.





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.