Avalanche Advisory February 14, 2011

There is a MODERATE avalanche hazard in the West Central Montana backcountry on wind-loaded slopes steeper than 30 degrees. Careful evaluation of snow and terrain is recommended during MODERATE conditions.

Good morning. This is Dudley Improta with the West Central Montana Avalanche Center’s advisory for February 14, 2011. Strong winds have loaded steep, exposed slopes in West Central Montana above 5000 feet. Dangerous conditions exist in this terrain. The avalanche hazard is LOW on terrain that is not wind-loaded and less steep than 30 degrees.

Weather and Snowpack Analysis

Saturday and Sunday morning strong winds buffeted the high mountains in our area.  Winds were generally recorded coming from the West and Southwest. Regional Snotel sites recorded 1-2 inches of snowfall from Sunday morning. On our tour in the Rattlesnakes Sunday we could see the wind moving that snow along the ridgetops. On Saturday, Adam Clark, a regular observer, reported hard wind slabs, overlying loose cold snow, were failing easily in stability tests on Wisherd Ridge, just Northeast of Missoula. This video shows our concern with wind-loading on the high, exposed terrain. (You’ll also note my count is a little off on the Extended Column Test – I count 14, not the correct 17)

Many weather stations recorded temperatures above freezing at elevation over the weekend. The warm weather is a bit of a Jekyll and Hyde situation. The warm temperatures will settle the snowpack in the long run, but during the warmest part of the afternoon the snow becomes less stable. It is easier to trigger an avalanche if you are on a steep slope during the heat of the day. Adam went ice climbing yesterday and sent us this photo of fresh avalanche debris from the South face of Kakashe Mountain in the Southern Missions. We suspect this is from a large wet snow slide initiated by the recent warm weather.

Weather Forecast and Avalanche Outlook

High pressure will continue over the region through Monday. A Southwest flow with moisture is predicted to move in Monday night. This flow may bring up to a foot of snow in the mountains Tuesday through Wednesday. The winds accompanying this event may be strong and load the lee slopes. I would expect the avalanche hazard to remain the same through Tuesday, with rising instability in the heat of the day. The overall avalanche hazard will increase if we get the snow and wind that is forecasted.

Ride and ski  safe and I trust you did not forget anyone today – Valentines Day 2011.

The next advisory will be issued Friday, February 18.

If you get out and see avalanche activity or want to send us quick snow observations please use our public observations formon the home page missoulaavalanche.org or write us at [email protected]