I think you would be fine. We had 60F today on the plane and ski boat. I would think that temps would be around the mid 60's by then on the plane. Keep in mind that the thermocline is usually right around the depth of the plane. It would be warmer just above the plane and on the rocks by several degrees. Some of our "regulars" are in 5mm with hood by then (you would want at least 3mm gloves though). Our river dives are good choices too - less depth, less wetsuit compression (more warmth), and temps in mid 60's by May.
---------- Post added April 12th, 2014 at 08:45 PM ----------
You can also join the Facebook group "Divers of Augusta" to see information re current temps, vis, and weekly dive plans. We have had way too much rain this winter and spring thus far, but it seems like that trend may be slowing down. Vis will pick up when it does.