Have a read ....
just change the numbers from 17 of 23 to 18 of 24.
http://avalancheinfo.net/Media/2008-09/2009 03 27 snowmobilers and avalanches.pdf
just change the numbers from 17 of 23 to 18 of 24.
http://avalancheinfo.net/Media/2008-09/2009 03 27 snowmobilers and avalanches.pdf