February 19, 2013 Avalanche Advisory

The avalanche danger in the west central Montana backcountry is MODERATE. It may be possible to trigger an avalanche on exposed leeward slopes above 7000 feet and steeper than 35 degrees.  All indicators point to LOW avalanche danger; we just cannot discount the winds that have been moving snow around at the higher elevations. MODERATE avalanche danger indicates heightened avalanche conditions in specific terrain features and the possibility of small avalanches in those specific areas. Those specific areas would be recently wind-loaded pockets on steep, exposed terrain above 7000 feet.

Good Morning! This is Dudley Improta with the West Central Montana Avalanche Center’s avalanche advisory for Tuesday, February 19, 2013.

Weather and Snowpack Analysis

Mountain temperatures are in the high teens to low twenties this morning. Above 7000 feet, winds are out of the southeast to southwest at 15mph, with higher gusts.  Over the weekend the area received some snow, accompanied by steady winds with gusts into the 30mph range. Lookout and Hoodoo Pass accumulated around 5 inches and the Rattlesnakes and the southern Missions received 6 to 8 inches. Remote weather telemetry recorded 4 to 5 inches at Lolo Pass, up to 9 inches in the central Bitterroots and 3 inches near Lost Trail Pass.

The snow that came in had a bit of moisture (snow water equivalent) to it and settled rapidly. Quick settlement is a good sign for stability. Wind is the name of the game as far as any avalanche conditions are concerned.

I was in the backcountry near Lost Trail Pass on Saturday and noted lots of wind. Near LT there was plenty of surface hoar before Sunday’s snow, but it looked like the wind had destroyed it as the snow came in. I was in the Rattlesnakes yesterday and we recorded steady 20mph winds with gusts up to 26mph. This wind, primarily out the south and east, was moving the snow onto leeward slopes. We tested some steep pockets with no reaction and steep terrain was getting skied; but we could not ignore the wind-loading that was going on.

Rattlesnakes wind 2/18/13 7900 feet

Rattlesnakes wind 2/18/13
7900 feet

The Bottom Line

I know, I know – we’ve been at MODERATE for a few advisories.  Again, the specific concern is for steep, recently wind-loaded pockets on, or near, exposed ridgetops at higher elevations (above 7000 feet).  Also treat steep couloirs or gullies at these high elevations as if they are wind-loaded. Those specific terrain features might harbor some awesome powder or a wind-slab.

I found a great sentence in a book  I’m reading that aptly describes dealing with snow on steep, avalanche prone terrain: “When interacting with nature, humans are denied certainty.”  Michael Crichton Micro

Weather Forecast and Avalanche Outlook

Mountain snows are expected for the next few days. Tonight and Wednesday appear to be the best bet for snowfall. The mountains along the Idaho  border should see the the most amount of snow. As of now, significant winds are not expected. The avalanche danger should remain the same for the next couple  of days.

If you would like to report on avalanche or  snow conditions use our public observations form or send us a note at  [email protected]  .

I will issue the next advisory Friday, February 22.

Education

There is a Level 1 class in the Bitterroot that begins March 1 and an avalanche awareness class in Victor that begins March 6.