Avalanche Advisory February 11, 2011

Good morning. This is Dudley Improta with the West Central Montana Avalanche Center’s avalanche advisory for February 11, 2011.

On slopes above 6000 feet that are wind-loaded and steeper than 35 degrees there is a CONSIDERABLE avalanche hazard. During CONSIDERABLE avalanche hazard careful snowpack evaluation, cautious route-finding and conservative decision making are highly recommended. On other slopes above 5000 feet and steeper than 35 degrees there is a MODERATE avalanche hazard.

Weather and Snowpack Analysis

On Monday, February 7 we had quite the snow event in the central and northern part of the forecast area. Some areas received up to 16 inches of snow in 48 hours accompanied by very strong winds. On Monday Steve issued an avalanche warning.

Although most areas have received a few more inches of snow since Monday; the winds have not abated.  Since Tuesday high mountain wind directions have been recorded from the Southwest, West, Northwest, North and Northeast. There is a good possibility of a wind slab or wind-loaded slopes on just about every aspect at elevation.

The Snow Bowl Patrol had significant wind slabs release on West and Southwest couloirs with their control work Tuesday morning. Skiers on Downing Mountain in the Bitterroots reported numerous human-triggered slabs on Wednesday. These photos, sent in by Colin Chisholm, show the localized slabs near Downing Mountain. Yesterday we noted lots of snow being moved by the wind along with impressive cornice buildup on East aspects in the Rattlesnakes.

The current conditions bring home the point of taking in the whole picture in your avalanche assessment. Almost all of our observers, including those of us in the Rattlesnakes were getting moderate to stable results with stability tests in our snow pits. Yet, all you had to do was look around at the how much the strong winds had moved, and were moving snow; to know that wind slabs were lurking on the lee terrain. Don’t be lulled into looking at one piece of information. New snow loads and high winds are your biggest clues right now.

Weather Forecast and Avalanche Outlook

On Friday high pressure is predicted to collapse and allow increased moisture to move into Western Montana. Temperatures may rise above freezing up to 8000 feet through the weekend. RISING TEMPERATURES IN THE AFTERNOON WILL INCREASE THE CHANCES OF NATURAL AND HUMAN-TRIGGERED AVALANCHES.

Saturday may see increased winds with the potential for possibly heavy snow in the Northern Bitterroot, Rattlesnakes and Southern Missions and Swans. More winds and more snow equals continuing avalanche hazard. Perhaps some nice fresh powder on some low angled treed slopes is the place to be for the next few days.
I will issue the next advisory on Valentine’s Day, 2011. Ride and ski safe, have a great weekend and don’t forget your special friend.

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 missoulaavalanche.org or write us at [email protected]