Avalanche Warning January 9, 2009

Posted: January 9, 2009 – 06:30

Good morning. This is Dudley Improta with the West Central Montana Avalanche Center’s avalanche advisory for January 9, 2009. Today’s advisory is dedicated to the memory of Ben Richards (photo at the right). 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, although the advisory can give you valuable information for assessing snow conditions for the next 48 hours.

Steve Karkanen issued an avalanche warning on Wednesday; we are continuing that warning through today. An avalanche warning continues to be in effect for the mountains of West Central Montana above 5000′. The most recent storm has deposited warm dense snow on top of colder snow. This snow came in with high winds from the Southwest. The avalanche danger is HIGH. Natural and human triggered avalanches are likely. Unstable slabs exist on all aspects and slopes steeper than 30°. This warning includes the Bitterroot Range from Lost Trail Pass to Lookout Pass, the Rattlesnake Mountains (including Sheep Mountain in the Lower Blackfoot) and the Southern Mission and Swan Ranges near Seeley Lake. Extensive skill, experience and knowledge are necessary for safe travel in the backcountry during HIGH avalanche conditions.

Weather and Snowpack Analysis
Snow stability testing is showing very easy failures in the top layers of the snowpack. At 8000′ in the Rattlesnake Mountains this surface slab is 2 feet thick! This photo shows the bed surface and depth of this slab.
.Rutschblock Test Photo
This condition is widespread in West Central Montana and is on all aspects. We didn’t get rain at high elevation as predicted, we got dense heavy snow. This snow was deposited on colder snow on the surface. Reports from the Bitterroot noted 31” of new snow for the week. Along with this storm came the wind. The winds at elevation were 30mph with gusts up to 50mph. The deep instability that has been pestering us is still present but the main concern is the surface slab that could be triggered easily. This slab is present on all aspects plus Northwest, North and Northeast slopes are wind-loaded above 5000′.

Current Avalanche Danger
Throughout the advisory area and on all aspects above 5000′ the avalanche danger is HIGH on all open slopes steeper than 30°. Natural and human triggered avalanches are likely.
Below 5000′, the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. There is still some very weak snow near the ground at lower elevations. Any open, steep slopes are suspect. Reports from Lolo Pass (at 5600′ elevation) showed stronger snow but the worrisome weak snow near the ground continues to be a concern. Observations from around the region pegged the snow/rain line at 5600′.

Weather Forecast and Avalanche Outlook
A weak high pressure with colder air is expected to move into the region and extend into the weekend. A Northwest flow aloft should produce light snow. The best chance for snow looks like Saturday afternoon and Saturday evening.
This surface instability should begin to settle out within 48 hours. The deep weak snow from the cold weather in December is still with us, but beginning to strengthen.

The next advisory will be issued January 12, 2009.
If you have any snow observations or questions please e-mail us at [email protected]

For specific Lookout Pass / St. Regis Basin avalanche information visit the Idaho Panhandle National Forest at Idaho Panhandle National Forest Avalanche .