A HELI CAPT INADVERTENTLY ENTERED IMC WHILE FLYING UNDER VFR.

Narrative

I DEPARTED ZZZ AT APPROX XA00 RESPONDING TO A CALL. IN ENRTE; I ENCOUNTERED NOTHING UNUSUAL EXCEPT A FEW PATCHES OF LOWER CLOUDS TO THE S AND W OF THE LNDG ZONE. AFTER A BRIEF ORBIT TO MAKE WAY FOR A DEPARTING ACFT; I LANDED. I WAS LOADED IN APPROX 10 MINS AND WE DEPARTED ON A DIRECT RTE. ZZZ ON DEP; I OBSERVED THE WX IN THE AREA APPEARED CLR; I WAS ABLE TO SEE STARS AND THE DISTANT LIGHTS. I INITIALLY CLBED TO 11000 FT TO ENSURE ADEQUATE TERRAIN CLRNC AND SELECTED A HEADING; WHICH WOULD STEER ME WELL CLR OF TERRAIN. DURING THE CLBOUT; I FOUND MYSELF INADVERTENTLY POSITIONED BTWN TWO CLOUD LAYERS AND GRADUALLY LOSING VISUAL REF. I BRIEFLY SAW THE STARS ABOVE ME AND THOUGHT I COULD GET ON TOP BY CLBING A LITTLE HIGHER. IT WAS AT THIS TIME I REALIZED I HAD LOST VISUAL REF AND ELECTED TO TRANSITION TO THE INSTS. I CONTACTED ARTCC AND APPRAISED THEM OF MY SIT. CTR ISSUED ME A SQUAWK CODE AND SUGGESTED I CLB TO 12500 FT. SHORTLY AFTER MY INITIAL CONTACT WITH ARTCC; I WAS ABLE TO CLRLY ESTABLISH VISUAL REF WITH THE TERRAIN AND PROCEEDED DIRECTLY TO ZZZ.