Eastern Gray squirrel

Wow! We have all the possibilities for your area here. I do not think it is the fox squirrel, which would have an orange underside, not a white underside. Fyn's suggestion of the red squirrel could be a possibility but they are much smaller and less apt to climb right on to a porch railing. This is Sciurus carolinensis, which can sometimes have the brownish band around the body yours has, making it confusing to separate from the other species.