Keystone opened the bottom of the mountain on Friday and Arapahoe Basin opened its upper slopes, meaning both areas will be offering top-to-bottom skiing this weekend for the first time this season. Loveland, meanwhile, will open a second lift on Saturday, bringing the number of open trails to three. Keystone now has eight of its 128 trails in operation, according to its official terrain report, and Arapahoe Basin will have five runs in operation this weekend.