PA34 PLT ENCOUNTERED UNFORECAST HVY PRECIP AND ON RETURN TO DEP ARPT EXPERIENCED ALTDEVS DUE TO TURB.

Narrative

I DEPARTED AFTER GETTING A WX BRIEFING VIA FSS ON THE PHONE AND WSI. I WAS HANDED OFF TO ZTL WHO ADVISED THERE WAS MODERATE TO EXTREME PRECIP 30 MI AHEAD AND ASKED IF I HAD WX RADAR. I DIDN'T HAVE WX RADAR AND ADVISED THEM; ATC REPLIED THEY WOULDN'T RECOMMEND TRYING TO GO THROUGH IT AND ASKED IF I GOT A WX BRIEF PRIOR TO MY DEP. I WAS SURPRISED THEY ASKED THAT DUE TO PRIOR TO MY DEP THERE WAS NO WX IN THE AREA THEY DESCRIBED. I ASKED IF THE WX WAS NEAR ATHENS AND IF NOT COULD I DIVERT THERE. ATC SAID ATHENS WASN'T GOOD EITHER. I ELECTED TO RETURN TO MY DEP ARPT 40 MI AWAY. I WAS CLRED DIRECT AS I TURNED N I ENCOUNTERED MODERATE/SEVERE TURB CAUSING AN IMMEDIATE 400 FT DROP IN ALT FOLLOWED BY AN IMMEDIATE GAIN OF 600 FT. ATC NEVER ASKED ABOUT MY ALT CHANGES. I GAVE A PIREP TO FSS REGARDING THE TURB. ONCE ON THE GND I RECHKED WX VIA FSS WHO ADVISED THEY SAW NO PROBS/PRECIP FOR MY RTE EXCEPT AT MY DEST BUT IT WOULD BE GONE BY THE TIME OF MY ARR. I ALSO SPOKE WITH MY DISPATCH AND ADVISED THEM OF A DELAY AND WHAT ATC SAID. DISPATCH LOOKED AT THEIR WX RADAR AND ALSO SAID THERE WAS NOTHING THERE. WSI ALSO SHOWED NO WX IN THE AREA DESCRIBED BY ATC. I DEPARTED AND HAD NO PRECIP DURING THE FLT. I WAS SURPRISED BY THE DIFFERENCE IN WHAT ATC SAW AND WHAT WAS ACTUALLY OUT THERE. THE FACT THAT ATC QUESTIONED ME ABOUT THE WX HAD ME SECOND GUESS MYSELF AND THAT I POSSIBLY MISSED SOMETHING. I DECIDED I MADE THE RIGHT DECISION TO RETURN AND BE ON THE SAFE SIDE. THE WHOLE THING COULD HAVE BEEN AVOIDED HAD I BEEN FLYING AN ACFT WITH WX RADAR.