C208B ACFT ON VFR FLT PLAN ENCOUNTERED DETERIORATING WX AND RPTR PLT HAD TO DIVERT WHILE HAVING DIFFICULTY MAINTAINING VFR CONDITIONS. AN IFR CLRNC WAS OBTAINED THROUGH A TRACON FACILITY AND RPTR CONTINUED IFR.

Narrative

I WAS PROCEEDING FROM VIS TO OAK VFR; WITH VFR SVCS BEING SUPPLIED BY STOCKTON APCH. I WAS HEADING TOWARDS MOUNTAINOUS TERRAIN AND THE CLOUD COVER WAS LOWERED OVER THAT AREA. I COULD SEE STILL 35-40 NM TO THE PASS THAT I USUALLY GO THROUGH WHEN I AM FLYING THIS RTE. STOCKTON APCH HAD ME SQUAWK xxxx. I CONTINUED ON DSNDING AND I WAS EASILY MAINTAINING CLOUD CLRNC AND TERRAIN CLRNC. THE AREA THAT THIS WAS OCCURRING IS VERY SPARSELY POPULATED. AS I APCHED MY PASS CONDITIONS WERE CHANGING DRAMATICALLY TO THE WORSE. THERE WAS A SMALL FRONT THAT WAS APCHING THE AREA AND A LOT OF OTHER PEOPLE WERE GETTING CAUGHT OUT. THE OAK ATIS HAD EARLIER RPTED 20 MI VISIBILITY; FEW CLOUDS AT 2500 FT AND OVCST AT 6500 FT. I WAS MONITORING BAY APCH; WHEN THERE WAS A FLOOD OF REQUESTS FOR IFR CLRNCS AND APCHS GOING INTO OAK AND HWD. MY PASS WAS CLOSING IN FAST; SO I REVERSED COURSE. UPON REVERSAL I NOTED THAT CONDITIONS BEHIND ME HAD DECAYED. I WAS ONLY MARGINALLY ABLE TO MAINTAIN VFR; AND KNEW THAT MY CHANCES OF GETTING A CLRNC EXPEDITIOUSLY WAS NOT VERY LIKELY UNLESS I DECLARED AN EMER. I FLEW OUT OF THE AREA MAINTAINING THIS MARGINAL VFR BY BASICALLY KEEPING THE TERRAIN IN SIGHT AND GLIMPSING AT THE MOVING MAP DISPLAY ON THE GPS. I DID MY BEST TO AVOID ANY CTLED AIRSPACE THOUGH I MAY HAVE INADVERTENTLY STRAYED INTO SOME. I WAS PRETTY SCARED AND TRIED TO MAINTAIN A SAFE ALT ABOVE TERRAIN. AFTER FLYING WBOUND I WAS ABLE TO GET INTO A CLR AREA; AND CIRCUMNAV THE WX TILL I GOT TO TRACY ARPT; WHERE I CONTACTED STOCKTON APCH AND GOT AN IFR CLRNC TO OAK. I WOULD SAY THAT IN THE FUTURE I WILL REQUEST AN IFR CLRNC WHEN THE POTENTIAL OF THESE KINDS OF CONDITIONS EXIST PRIOR TO GETTING INTO CONGESTED AIRSPACE. I PROBABLY SHOULD HAVE ATTEMPTED TO CONTACT BAY APCH ANYWAY TO SEE IF THEY COULD ASSIST ME. IF THINGS WOULD HAVE GOTTEN MUCH WORSE I WOULD HAVE HAD TO FACE MY EMBARRASSMENT FOR NOT HAVING FLOWN IFR; AND DECLARED AN EMER. AT NO TIME WAS I REALLY CLOSE TO TERRAIN; RADAR ALTIMETER WAS SET TO 1000 FT AND IT NEVER ALERTED. THE SIT IS SOMETHING I AM EMBARRASSED ABOUT; I SHOULD HAVE NEVER LET MYSELF GET THERE. I GUESS WE ALL HAVE A LAPSE OF REASON AT TIMES.