The basic minimum roof snow load for Spokane County is 30 pounds per foot. However, areas within Spokane County have snow loads as high as 150 pounds per foot. The Scout mapping system available on the County website has snow load maps available on one of the layers to the public. This number provided is the ground snow load, which must be multiplied by .7 to obtain the roof snow load.
http://cp.spokanecounty.org/scout/SCOUTDashboard/ property addressing.