HELI ON A VFR FLT WAS FORCED INTO IFR CONDITIONS BY A LINE OF TSTMS.

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4 PAX AND CREW OF 2 FULLY IFR CAPABLE. NO FUEL OR WX AVAILABLE AT DEP. FLT WAS FORCED S OF COURSE DUE TO A LINE OF UNFORECASTED TSTMS EXTENDING FROM MOBILE; AL; TO 30 NM S OF GULFPORT AND GROWING TO THE SW FROM THERE (GULFPORT ATIS). WE PROCEEDED SW AT 2000 FT TRYING TO GET AROUND THESE STORMS UNTIL WE FOUND A SPACE BTWN 2 CELLS; THE RADAR SHOWED THE OTHER SIDE WAS ONLY 6 MI AWAY; WE DSNDED TO 500 FT AND COULD SEE SOME 4-5 MI THROUGH THIS HOLE. I ELECTED TO TRY GETTING THROUGH THIS HOLE AS WE HAD THE CHANDLER ISLANDS FOR GOOD LANDMARK AND THE VISIBILITY WAS WELL ABOVE VFR. AFTER PROCEEDING INTO THIS HOLE FOR 6 MI THE RAIN STARTED TO INCREASE; AND WE TRIED TO TURN AROUND THE HOLE HAD CLOSED IN BEHIND US; SO WE STARTED A CLBOUT TO MSA 1500 FT FOR THE AREA ON THE ORIGINAL HDG. WE STILL HAD VERT VISIBILITY BUT BELOW VMC; AT 1200 FT WE FLEW OUT OF THE RAIN WITH WX NOW 2000 FT AND 10 MI WE CONTACTED NEW ORLEANS APCH AND CONTINUED ON TO MSY VFR. WE HAD INTENDED TO DECLARE AN EMER/INADVERTENT IFR AT 1500 FT WITH NEW ORLEANS APCH; BUT ONCE WE WERE VFR WE JUST REQUESTED VFR ADVISORY AND CLRNC INTO THE CLASS B AIRSPACE.