January 15, 2013 Avalanche Advisory

The avalanche danger in the west central Montana backcountry is MODERATE.  It’s possible to trigger avalanches on exposed wind-loaded slopes steeper than 35 degrees. Also, there are weaknesses where the snowpack is shallow and around rocks and rock outcroppings.

Good Morning! This is Dudley Improta with the West Central Montana Avalanche Center’s avalanche advisory for Tuesday, January 15, 2013.

 Weather and Snowpack Analysis

Mountain locations have warmed into the double digits this morning and the area received 2 to 4 inches of snow yesterday afternoon and evening. Winds were intermittent but strong in the mountains Sunday night and Monday.

The snow from the storm that rolled through last Wednesday and Thursday seemed to settle quickly. Temperatures were very cold over the weekend. The cold temperatures made for good skiing and riding conditions; even on the sun-exposed slopes (we did have some nice sun on Sunday).  But, these temperatures have weakened the snow in areas where it is shallow and around rocks and rock outcroppings.

I was in the southern Swans with the Yurtski folks through Monday and we found overall stable snow. That being said, I wouldn’t totally discount the layer underneath last week’s storm snow. This layer was failing on multiple aspects with moderate strength and low energy in my pits. The cold temperatures can allow weaknesses to persist. I would continue to look for a weak layer in the top 15 to 24 inches of snow when considering steep slopes.

An observation from Downing Mountain Lodge in the Bitterroots was reporting close to the same conditions; last week’s storm snow failing with moderate strength in tests. Wind slabs exist on the lee slopes in the area but no recent activity was noted. An observation from Anderson Mountain in the southern Bitterroots indicated stable conditions with lingering caution about last week’s storm snow.

Tim and Dave were in the Rattlesnakes yesterday. Their observations also indicated MODERATE danger. And, if you look at Dave’s pit profile, you do see weaknesses to be wary of.

As if to prove a point about keeping an eye on weak snow with the cold temperatures – we did receive a report of a skier-triggered avalanche in the Rattlesnakes near Snowbowl that occurred yesterday. Details are not complete, we do know all parties made it out. We will relate more info as it becomes available.

The cold temperatures are keeping the surface snow weak and are creating weaknesses where the snow is shallow and around rocks or rock outcroppings (trigger points).  Don’t be led astray by the absence of obvious clues (recent avalanches, collapsing, whoomphing).  I said it above – check for weak snow when considering steep slopes.

Weather Forecast and Avalanche Outlook

Decreased precipitation is expected with a dry Wednesday. Inversions should cause a warming at high elevations. This warming may further stabilize the snowpack. For now, look for weakness in the snow in the top 15 to 24 inches of the snowpack and for weakness in shallow snow or near rocks  if considering riding steep terrain.

More Info

Kettlehouse – this Wednesday benefits missoulaavalanche (these guys are keeping this thing going). 5-8pm. Sledders welcome!

Keep those cards and letters coming folks! Public Observations.

I will issue the next advisory Friday January 18th.