March 26, 2013 Avalanche Advisory

The avalanche danger is now LOW (Level 1) in the west central Montana backcountry.  Although we’re dropping the danger level to LOW, small avalanches are still possible in isolated areas or on extreme terrain.

On sunny days or whenever the surface temperature warms to 32 degrees F on slopes steeper than 35 degrees, the avalanche danger will increase to MODERATE (Level 2). Expect to see point release wet snow avalanches involving the new snow we received this past week.  Some of these can get quite large on the longer paths as more snow is entrained as they move down slope.

Good morning, this is Steve Karkanen with the Tuesday, March 26, 2013 avalanche advisory from the West Central Montana Avalanche Center.  This will be the final Tuesday avalanche advisory for the season.

 

Weather and Snowpack

In the past week our mountains picked up anywhere from 8 to nearly 16 inches of new snow through Saturday. Mountain temperatures have stayed below normal for this time of year which made for exceptional skiing and riding this past weekend. The clouds cleared Sunday and although air temperatures remained cool, the sun rapidly warmed things up especially on any slope with a steep sun angle.

With the cooler and clear conditions all aspects on the north half of the compass remain powdery while aspects on the south half get baked.  This snow bonded well to the crust that formed more than 10 days ago and no major sloughs or loose snow avalanches were seen or reported on the steep lines people were skiing this weekend.  Many skiers and riders reported wet snow conditions on the southerly aspects by early afternoon Sunday.

Temperatures dropped back into the teens again early Monday then warmed into the thirties by afternoon.  This morning, temperatures are in the twenties and are expected to ramp back up into the forties this afternoon.  Ridge top winds are light this morning.

 

What’s Important Now

This diurnal temperature variation puts all but the most shaded snow into a melt/freeze cycle, which is good for stability, maybe not so good for skiing. For a sled however, this is go-anywhere snow. You just have to pay attention to the steep, sunny aspects and avoid them when things warm to the melting point.

Seeing pin wheels, point release wet slides or sinking up to your knees in wet snow are good indicators of changing and possibly more dangerous conditions.  Move to the more shaded and cooler terrain.

Cornices grew even bigger during the 40-70mph winds we experienced last week and they will be touchy as it warms up.  Give them a wide berth. Don’t tempt fate by hucking off of or high-marking a slope directly underneath one of these monsters.

 

Weather Forecast and Avalanche Outlook

Missoula Weather is forecasting a ridge of high pressure to linger over the Northern Rockies for much of the week. The atmosphere will continue to warm and there’s a chance for minor showers. Temperatures above 6000 feet will continue dropping well below freezing at night and warm into the forties in the afternoon.

Avalanche danger will remain similar under these conditions with LOW danger on most slopes bumping up to MODERATE on steep terrain exposed to the sun.

I will issue the next advisory this Friday, March 29, 2013.

Friday, April 5, 2013 will be the last advisory of the season.