C172 ENCOUNTERED ICING ON A NIGHT VFR FLT. PLT WAS ABLE TO OBTAIN IFR CLRNC AND EVENTUALLY EXIT ICING CONDITIONS.

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ON A SOLO NIGHT FLT TO SNS INTENDED TO BE ACCOMPLISHED VFR; LOWER THAN FORECASTED CEILINGS WERE ENCOUNTERED E OF THE ROM VOR ABOUT 30 MINS INTO MY FLT. BECAUSE OF TERRAIN CONSIDERATIONS I ELECTED TO GO HIGHER; SEEING THAT THERE WAS ROOM TO FLY VFR AND CLB BTWN THE STRATUS LAYERS TO A HIGHER ALT AND CONTINUE VFR WITH GND CONTACT. UPON REACHING THE HIGHER ALT; CLBING FROM APPROX 5000 FT TO 6500 FT IT BECAME EVIDENT THAT APPROX 15 NM AHEAD I WOULD ENCOUNTER IMC. I COULD STILL SEE BTWN THE LAYERS ABOVE ME; AND I COULD SEE STARS IN BTWN AND OTHER ACFT CLEARLY; INDICATING TO ME VFR CONDITIONS ON TOP; AND I KNEW THAT I WOULD HAVE TO CLB TO 8000 FT AS AN MEA IF I PICKED UP AN IFR CLRNC. SO TO BE SAFE; SEEING AS HOW IT WAS DARK AND IT WAS MARGINAL WX CONDITIONS; I ATTAINED A POP-UP IFR CLRNC FROM ZOA; KNOWING THAT I WOULD CLB TO 8000 FT AND BE IN THE CLR. THE TEMP AT 6500 FT AT MY TIME OF DECIDING TO DO THIS WAS 4-5 DEGS C. UPON REACHING 8000 FT I LEVELED OFF AND IT WAS ABSOLUTELY DARK OUTSIDE. IT BECAME CLR TO ME THAT I HAD FLOWN INTO A LAYER I HAD NOT SEEN DUE TO THE DARKNESS. THE TEMP AT THAT ALT WAS -2 DEGS C. IT WAS CLR THAT A LIGHT AMOUNT OF RIME ICE WAS FORMING ON THE LEADING EDGE UPON VISUAL INSPECTION. KNOWING HOW EVEN A LITTLE ICE CAN BE DANGEROUS; I TRIED SEVERAL DIFFERENT ALTS TO SEE IF I COULD GET OUT OF THE ICE. STARS ABOVE ME WERE VISIBLE FAINTLY SO I THOUGHT I WAS CLOSE TO THE TOP OF THE STRATUS LAYER; SO I FIRST ELECTED TO CLB TO 9000 FT. UPON REACHING 9000 FT WITH STARS STILL VISIBLE ABOVE ME THE ICING STOPPED ACCUMULATING FOR A FEW MINS; BUT AT THE COLD TEMP I WAS CERTAIN THAT THE LITTLE ICE I DID ACCUMULATE WAS NOT GOING TO SHED. BASED ON MY KNOWLEDGE OF THE LCL TERRAIN AND METEOROLOGY I KNEW THAT AS I APCHED THE HIGHER TERRAIN IT WAS LIKELY THAT THERE WOULD BE HIGHER CEILINGS AS WELL THAT WOULD PUT ME BACK INTO THE ICE; KIND OF HOW A STRATUS LAYER WILL CLB OVER A HILL AND BE FORCED TO DEVELOP UPWARDS. I WAS WELL INTO A BAD SITUATION AT THAT POINT; AND I FELT DISGUSTED WITH MYSELF THAT I LET IT GET THIS FAR OUT OF HAND. AFTER BEING AT 9000 FT FOR A FEW MINS IT BECAME CLR THAT I WAS GOING TO ENTER ICING CONDITIONS AHEAD AS MY FORWARD AND UPWARD VISIBILITY WAS REDUCED. AT THIS TIME I REQUESTED LOWER IN AN ATTEMPT TO GET TO A WARMER TEMP. I WAS GRANTED 7000 FT WHICH WAS RIGHT AT 0 DEGS C; AND WAS THEN GRANTED 6500 FT WHICH PUT ME AT +1 DEGS C. AT THIS POINT I WAS IN CONSTANT IMC HEADED NWBOUND TOWARD SNS. I KNEW THAT THE FURTHER W I WOULD GO THE LOWER THEY WOULD ALLOW ME TO GO; SO I WAS ASSURED THAT THE RISK OF ICING WAS REDUCED AHEAD. THE REST OF THE FLT PROVED UNEVENTFUL WITH NO FURTHER ACCUMULATION OF ICING. MY MISTAKES WERE MANY IN RETROSPECT. ALTHOUGH I HAD ATTAINED AN ONLINE BRIEFING A FEW HRS EARLIER WHEN I LEFT SNS I DID NOT GET ADEQUATE UPDATED INFO FOR MY RETURN FLT; AND I RELIED ON THE FORECAST I HAD RECEIVED A FEW HRS EARLIER AND MY EXPERIENCE FLYING THE SAME RTE FROM SNS IN GOOD VFR CONDITIONS. I KNOW NOT TO TRUST IN SEEING VFR CONDITIONS; ESPECIALLY AT NIGHT TO MAKE A GO DECISION TO CONTINUE INTO A SITUATION THAT CAN BE DETERIORATING METEOROLOGICALLY. JUST BECAUSE YOU SEE CLR DOESN'T MEAN YOU'LL GET THERE; AND IT ALSO DOESN'T MEAN IT'LL BE THAT WAY WHEN YOU GET THERE. AT NIGHT; THAT METHOD OF FLYING CAN LEAD TO A BAD SITUATION. I'VE LEARNED FROM THIS SITUATION TO WEIGH MY OPTIONS MORE CAREFULLY AND RELY LESS ON WHAT I CAN SEE AT NIGHT IN MY DECISION MAKING PROCESS. THE SOLE FACT THAT I SAW STARS AND OTHER ACFT DOESN'T MEAN THAT I SHOULD CONTINUE A FLT AT NIGHT INTO MARGINAL CONDITIONS. THERE WERE ALSO MANY VFR ARPTS BACK IN THE CENTRAL VALLEY WITH HOTELS NEARBY THAT WOULD HAVE BEEN A BETTER OPTION THAN INADVERTENTLY ENCOUNTERING ICE ON MY FLT TO SNS. FROM NOW ON I'M GOING TO CONSIDER MYSELF IFR ONLY ON NIGHT CROSSCOUNTRIES; AND IF THERE IS EVEN A POSSIBILITY OF FORECASTED ICING ALONG MY RTE I AM NOT GOING TO BE TAKING AN ACFT NOT APPROVED FOR KNOWN ICING.