Jan 30, 2012 @ 6:02 am

January 30, 2012 Avalanche Advisory

Above 6000 feet on wind-loaded terrain steeper than 35 degrees there is MODERATE AVALANCHE DANGER in the west central Montana backcountry. Natural avalanches are unlikely, human-triggered avalanches are possible. On all other terrain above and below 6000 feet, there is LOW AVALANCHE DANGER. Natural and human-triggered avalanches are unlikely.

Good Morning! This is Tim Laroche at the West Central Montana Avalanche Center with your backcountry avalanche advisory for Monday, January 30th, 2012.

Weather and Snowpack Analysis

The next storm system is upon us and is favoring the Montana/Idaho border where 3-4 inches of high density snow has fallen overnight in the Hoodoo Pass and Lolo Pass areas. Other locations have picked up an inch so far at 4 am. Winds blew hard yesterday gusting into the mid 30’s at higher elevations out of the west and southwest. Currently, winds are blowing 8-10mph and gusting in the 20’s out of the south. Mountain temperatures are in the low 30’s and it’s snowing.

The high density snow we have received the past week and warming temperatures have helped to consolidate, settle, and strengthen our snowpack. Steve and I toured the Hoodoo Basin area yesterday and found a deep and mostly stable snowpack. Dudley and Elizabeth were in the Rattlesnake Mountains all weekend instructing a level 1 avalanche course and they reported moderate stability scores with no propagations in multiple locations on all aspects. Check out our latest pit profiles here. The persistent weak layers that have been concerning us have gained strength and are starting to break down.

The storm that arrived yesterday is bringing another round of high density snow and wind. The new snow should bond well with the old snow surface, but you will want to pay attention to fresh wind slabs that form near ridgelines on leeward aspects and where gullies and sub-ridges have been cross-loaded. These fresh drifts should be manageable for the most part and will settle out over the next couple of days with the warm temperatures we are experiencing.

We have not been able to get the old, now deeply buried, weak layers to fail consistently recently. Given the variability in our snowpack this season, you will want to dig down and see if these layers exist and how they may react on the slopes that you intend to ride.  You will want to pay particular attention to shallow, steep areas where these weak layers are still present and potentially still reactive.

Weather Forecast and Avalanche Outlook

The current mild and moist weather system will continue through today with falling temperatures this afternoon. Winds will turn to the west and blow in the 20-30mph range. Daytime temperatures will remain in the low to mid 30’s and we should see additional snow accumulations of 3-5 inches. We will see some weaker storms through the course of the week bring a couple of inches of snow at a time until Thursday, when we begin to transition to a high pressure scenario.

I expect the avalanche danger to remain the same this week as we keep getting small bursts of precipitation.

Steve will issue the next advisory on Friday, February 3rd.

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.