January 11, 2010 Avalanche Advisory

Posted 0700 on January 11, 2010.

Good Morning! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Monday, January 11, 2010.

Current Avalanche Danger

Avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible. Sun exposed slopes may warm enough today to see wet slides begin to occur. The avalanche danger will quickly rise to CONSIDERABLE when snow begins melting on these slopes.

Below 5000 feet, the avalanche danger is LOW.

Weather and Snowpack Analysis

Stability testing in the Rattlesnake and in the Bitterroot Mountains near Hoodoo Pass is showing a strengthened condition of both the buried surface hoar and the deep faceted snow near the ground.

The weakest slopes are those that are shallow where it is easy to punch through to the rotten snow at the ground especially near rocks and trees.

Ambient air temperatures Sunday reached into the mid to high 30’s so roller balls and a few wet point release avalanches moved on the sun exposed areas. The best skiing was in the shade but these colder slopes are also holding instabilities longer. The buried surface hoar layers that are about a foot to a foot and a half deep were failing but with more force required than a few days ago. Many people were out safely skiing steeper lines Sunday than we have seen all winter.

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting that warm and dry conditions will be present over high terrain through Monday afternoon. By Monday evening, a moist southwesterly flow and a weak embedded Pacific storm system will increase chances for precipitation. Expect snowfall amounts to be light.

The warmer temperatures will initially weaken our snow surface and I would expect to see wet avalanche activity on steep sunny slopes today. When the snow warms to this point, it is not a good time to be on or under anything steep. Remember, we still have faceted layers that cannot be trusted whenever conditions are changing. A small wet surface slide could easily step down to the weaker layers and cause a large avalanche.

These milder conditions will help to strengthen the overall snow structure but we are not completely free from seeing larger slabs bust out under the right amount of force.

We rely heavily on the many excellent observations people are sending us this winter. They help us produce a more accurate avalanche forecast since our resources are limited.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at [email protected] or call us at 406-530-9766. 530-9SNO.