Narrative:

I was under ATC control flight following VFR sacramento to monterey, ca. Requested by ATC to stay at 6500' told ATC will descend to 6000' MSL to avoid clouds overhead. Ceiling lowered and I descended to 5200' west/O telling ATC. They notified me that a large commuter aircraft had passed below at 5000' MSL. By monitoring communications I knew the other aircraft had me in sight before reaching my position. After event ATC told me I had changed altitude west/O notifying them. It was my error to change altitude west/O telling ATC. No fault found with ATC. It was my error. WX (clouds) was a significant factor in this.

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Original NASA ASRS Text

Title: CLOSE PROX GA-SMA ACR-LTT 14 NM EAST OF SJC.

Narrative: I WAS UNDER ATC CTL FLT FOLLOWING VFR SACRAMENTO TO MONTEREY, CA. REQUESTED BY ATC TO STAY AT 6500' TOLD ATC WILL DSND TO 6000' MSL TO AVOID CLOUDS OVERHEAD. CEILING LOWERED AND I DSNDED TO 5200' W/O TELLING ATC. THEY NOTIFIED ME THAT A LARGE COMMUTER ACFT HAD PASSED BELOW AT 5000' MSL. BY MONITORING COMS I KNEW THE OTHER ACFT HAD ME IN SIGHT BEFORE REACHING MY POS. AFTER EVENT ATC TOLD ME I HAD CHANGED ALT W/O NOTIFYING THEM. IT WAS MY ERROR TO CHANGE ALT W/O TELLING ATC. NO FAULT FOUND WITH ATC. IT WAS MY ERROR. WX (CLOUDS) WAS A SIGNIFICANT FACTOR IN THIS.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.