VISUAL SEPARATION IN USE ACR X TCASII RA HAD CONFLICT WITH ACFT Y. EVASIVE ACTION TAKEN.

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ACR X DSNDING INTO MHT; WAS CLRED TO 7000 FT. APCH CTL SAID THAT WE HAD TFC Y CLBING TO 6000 FT. I MOMENTARILY SPOTTED THE TFC AT OUR 11 O'CLOCK POS ON TOP OF A CLOUD BANK; I DON'T RECALL THE DISTANCE. I SOON LOST SIGHT OF THE TFC AS IT PROCEEDED OVER AN AREA CLR OF CLOUDS. I NEVER CALLED THE TFC IN SIGHT TO APCH CTL AS VISUAL CONTACT WAS LOST. WE LEVELED AT 7000 FT. APCH CTL RADIOED THAT OUR TFC HAD US IN SIGHT; WOULD MAINTAIN VISUAL SEPARATION; AND WAS CLBING OUT OF 6000 FT. WE WERE THEN CLRED TO 4000 FT. AT APPROX 6500 FT IN THE DSCNT; I SPOTTED OUR TFC AT OUR 12 O'CLOCK POS; APPROX 2 MI AHEAD; COMING DIRECTLY TOWARD US IN A RIGHT BANK. OUR TCASII WAS GIVING US A CLB RA. WITH THE TFC NOW IN SIGHT; THE CAPT DETERMINED THE SAFER COURSE OF ACTION WAS TO BANK R AND CONTINUE THE DSCNT. I IMMEDIATELY NOTIFIED APCH CTL THAT WE WERE IN THE TURN TO AVOID TFC. THE TFC PASSED OFF OUR L WING; AT OUR ALT; AND IN MY ESTIMATION; WAS WELL WITHIN 1/2 MI OF OUR ACFT. IT WOULD HAVE BEEN MUCH CLOSER HAD WE NOT SPOTTED THE ACFT AND MADE THE TURN.