We found this article to be a source of good information on the snow load for roofs. For your convenience, it contains the formula for measuring the weight of the snow on your roof. This will help you determine when to call in the professionals at GSM Roofing to remove or lessen your snow load and prevent serious damage to your building and the valuable contents inside. Here is the link.
http://www.accuweather.com/en/features/winter-break/how_to_keep_your_roof_from_col/45657