i think it is always good to go with native plants, and the best native choice for a snow fence in PA is Red Cedar - Juniperus virginiana. Problably you can find a pasture near you with tons of small Red Cedars to be had for the asking. They are quite easy to transplant, tolerant of hot and dry conditions, and make good wildlife habitat. I'd plant a double row with plants at about 4 foot centers in each row, rows about 4 feet apart, and stagger the plants in the two rows. Water them this first summer to make sure they become well established. The best non-native alternative is probably a spruce. Norway sprcue and blue Spruce both grow well throughout PA. Both are probably a little less tolerant of dry soils than Red Cedar, but still reasonably tough.