March 26, 2012 Avalanche Advisory

Expect LOW to MODERATE avalanche danger in the mornings, CONSIDERABLE avalanche danger in the afternoon.

Hello, this is Steve Karkanen with the West Central Montana Avalanche Center’s avalanche advisory for Monday March 26, 2012.

Weather and Snowpack Analysis

Since Friday, mountain weather has moderated with temperatures climbing into the 40’s and 50’s  in the afternoons then dropping back to near freezing at night.  The sun was out in full force Sunday so many slopes with direct exposure to the sun were active with natural point release wet snow avalanches involving last weeks new snow.  SNOTEL sites this morning are reporting that overnight temperatures remained above freezing.

Continued warm temperatures are bringing the overall snowpack to an isothermal condition which means that the temperature of the snow is the same from the surface to the ground. In this case 0 degrees c or 32 degrees F.  When a snowpack becomes isothermal it becomes unstable. At least until it goes through several melt-freeze cycles giving melt water a chance to form channels and adjust to the change in condition.

Weather Forecast and Avalanche Outlook

An approaching weather system will bring a good chance for showers and cooler temperatures in the next 48 hours. Initially this storm comes in warm with rain possible at elevations above 6000 feet.  Any rain introduced onto the snow will immediately add weight and weaken the snow structure.  During periods of rain the avalanche danger on any slope steeper than 30 degrees will quickly escalate to CONSIDERABLE where human triggered avalanches are likely and natural avalanches are possible.

As the storm front passes and cools, the avalanche danger will drop back to a MODERATE condition where human triggered avalanches are still possible but natural avalanches unlikely. A solid freeze will lock things up tight.

This will be the last Monday avalanche advisory of the season.  We will continue to post regular Friday morning advisories until April 6 which will be the last planned avalanche advisory of the season.

Tim Laroche will issue the next advisory on Friday, March 30, 2012.