West Central Montana Avalanche Center
March 26 Avalanche Advisory
posted: March 26, 2010

Hello! This is Steve Karkanen with backcountry avalanche information from the 
West Central Montana Avalanche Center for Friday, March 26, 2010.

Current Avalanche Danger

On any terrain steeper than 35 degrees above 6000 feet within the advisory area, the avalanche 
danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. 
On all other terrain above 6000 feet and at lower elevations, the avalanche danger is LOW. 
Natural and human triggered avalanches are unlikely.

During warm afternoons, or whenever it starts raining, the avalanche danger will quickly rise to 
CONSIDERABLE, when the probability increases dramatically that you will trigger an avalanche and 
that natural avalanches are a real possibility.

Weather and Snowpack Analysis

We received several inches of snow in the mountains earlier this week during the quick moving storm 
that came through the area Monday night and Tuesday. Stuart Peak and Twin Lakes SNOTEL received the 
most moisture with 1.3 and 1.5 inches of SWE respectively. The Northern Bitterroot picked up 1 inch 
at Hoodoo while the lower elevation passes received about .5 inches of SWE. The snow came in fairly 
warm and settled rapidly during the warm temperatures Wednesday and Thursday leaving most sites with 
modest new snow depths. The passes didn't gain any depth with the new snow.

Stability tests were showing the new snow to be bonding well and continued strengthening of the 
buried surface hoar layer about 16 inches deep. North aspects are the most suspect as we are still 
seeing clean failures when enough force is applied. We are seeing moderate range compression test 
scores with high quality shear planes on the old surface hoar layer. This is on the more shaded 
northerly aspects. Rutschblock scores were high (RB6, Q3) at both Lookout and Rattlesnake sites. 
Above 6000 feet near Lookout observers were seeing failures propagate but it was taking a lot of 
force to get these results.

We still see a lot of variability of the snowpack structure in Western Montana and the surface hoar 
layer we've been concerned about just keeps hanging in there. It remains important to look for this 
weakness especially after any new snowfall.

Weather Forecast and Avalanche Outlook

The National Weather Service Office in Missoula is forecasting that a Pacific storm system will 
bring a long duration light snow event into the Northern Rockies this evening through Saturday. 
Mountain passes are expected to receive as much as 6 inches during this period. By Saturday, these 
showers will cease and warmer temperatures will return as high pressure builds back into the area.

Expect moderate avalanche danger conditions to continue on the steeper terrain. As temperatures 
warm, expect to see many point release avalanches on steeper slopes in areas that receive 
significant snowfall amounts.