A C406 PLT RPTS SETTING ALTIMETER TO FIELD ELEVATION BEFORE DEP AND AFTER TKOF LEVELING 1000 FT HIGH BECAUSE OF ALTIMETER SETTING ERROR.

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PRIOR TO DEP THE CHKLIST CALLED FOR SETTING THE ALTIMETER WHICH I CHOSE TO SET TO THE FIELD ELEVATION. I HAD FLOWN THE ACFT 4 DAYS PREVIOUSLY AND DURING THAT TIME THERE WAS A LOW PRESSURE. TODAY THERE WAS VERY HIGH PRESSURE AND THE NEEDLE APPEARED TO BE ONLY ABOUT 40 FT OFF FROM THE FIELD ELEVATION. I RESET THE NEEDLE AND COMPLETED MY CHKLIST. UPON CLBOUT I WAS ASSIGNED 4000 FT BY AKRON/CANTON ATC. AS I WAS CLBING; ATC ADVISED ME THAT I WAS ASSIGNED 4000 FT AND GAVE ME THE ALTIMETER SETTING WHICH I ACKNOWLEDGED AND KEPT CLBING. AS I STARTED TO LEVEL OFF; I NOTICED THAT THERE WAS A PROB WITH THE ALTIMETER SETTING AS IT WAS WAY OFF FROM WHAT ATC HAD GIVEN ME. I RESET THE ALTIMETER TO THE CORRECT SETTING AND DSNDED TO THE CORRECT ALT. DURING THE PAST 4 DAYS; IT APPEARS THAT THE PRESSURE HAD CHANGED JUST ABOUT EXACTLY THE AMOUNT TO CHANGE THE ALTIMETER BY 1000 FT AND I HAD JUST SET THE LARGE NEEDLE TO WHAT I HAD THOUGHT WAS THE CORRECT FIELD ELEVATION WITHOUT BACKING UP THE THOUSANDS NEEDLE.