Avalanche Advisory March 25, 2014
There is MODERATE avalanche danger in the West Central Montana backcountry above 5000 feet, on slopes 35 degrees and steeper. MODERATE means heightened avalanche conditions in specific terrain. Steep slopes at higher elevations (>5000 feet) may produce avalanches, particularly during the warmest parts of the day.
Good Morning, this is Dudley Improta with the West Central Montana avalanche advisory for March 25, 2014. This danger rating does not apply to operating ski areas and expires at midnight tonight (March 25).
Our last scheduled avalanche advisory for the season will be this Friday, March 28.
Weather and Snowpack
This morning west and southwest mountain winds are blowing 12 to 20 mph and gusting into the upper 20’s. Mountain temperatures are ranging between 19 (F) in the southern Missions to 32 (F) at Saddle Mountain near Lost Trail Pass. Today may be the end of the nice weather for awhile.
I hiked into the Rattlesnakes yesterday and observed a lot of point releases on steep slopes during the heat of the day. These types of slides usually aren’t a problem, unless you get caught in a big one and it carries you into rocks or trees. We got a public observation from the Bitterroot yesterday that mentioned ice crusts. I found this “double crust” in the Rattlesnakes yesterday (Rattlesnakes Pit Profile); and though my pit tests were showing good strength and moderate energy, I wasn’t comfortable with the layering. I would look for this weakness if considering steep terrain.
The guides at Yurtski (southern Swans) found the “double crust” in their snowpits as well. They saw and triggered some small wet slides during the afternoon on southerly exposures.
Tim and Travis took the sleds into the Spruce Creek area near Lolo Pass. They saw the same “double crust”, albeit with more snow sandwiched in between (Spruce Creek Pit Profile). They noted loose, cold snow sluffing on steep northerly slopes, evidence of cornice releases and point releases near rocks (most likely during warm periods). As Travis put it “specific terrain has problems; everything else looks low”.
These crust formations in the snow (from the intermittent sun, then snow, then sun) are widespread. Folks are getting failures in pits throughout the advisory area. You wouldn’t have to dig too deep to look for an instability, and it may pay off.
Cornices are large and will continue to be a concern through Spring. Warmer temperatures can make them more likely to fail. Cornices are unpredictable in the Spring; best to avoid them during the warm part of the day.
Weather Forecast and Avalanche Outlook
The sun was out in the morning yesterday and then a bit of cloud cover came over. This kept things from heating up too radically. The warm temperatures offset with some clouds should help the snow continue to settle.
Scattered mountain snow showers are predicted to return tonight and persist into the weekend. Snow levels will begin around 5000 feet and lower to 4000 feet by Thursday. With new snow, I would expect the avalanche danger to remain MODERATE on steep slopes.
Generally, the first rain-on-snow event in the Spring causes us the most concern. That being said, anytime it rains on steep slopes the immediate effect adds weight and loosens the snow. You should avoid steep slopes during and immediately after rain events.
Ski and ride safe; have a good week.
I will issue our last regular advisory on Friday, March 28, 2014.