Welcome to the forums. I concur with everyone else that it's a T. s. parietalis. A very handsome one at that, thank you for sharing. I find it interesting to see how snakes vary throughout their range. Your snake has an olive coloured head, while all the ones I have come across here in Alberta have the same black on their head that is on the rest of the dorsum.
Also in comparison to Tommy's T. radix pictures, the ones around here are more solid black as opposed to the checkerboard background.

Ian