LAST WX RECEIVED BY FLC ON APCH WAS THREE QUARTER MI. LEGAL FOR LNDG; SO FLT CONTINUED APCH AND LANDED. UPON LNDG; TWR OPENED FOR BUSINESS AND ANNOUNCED ONE QUARTER MI VISIBILITY.

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WE WERE 15 MINS OUT OF GREENVILLE APPROX 20 MINS BEFORE TWR OPENED. WE CALLED OUR COMPANY ON GND AT GREENVILLE FOR APPROVED WX. WE WERE GIVEN 300 OBSCURED 3/4 VISIBILITY IN FOG. BEFORE CLRING US FOR APCH; CENTER ASKED IF WE HAD THE WX. WE TOLD HER WHAT WE RECEIVED; SHE ASKED IF IT WAS BELOW OUR MINS -- IT WASN'T. (APCH REQUIRED 3/4 MI VISIBILITY WITH TWR CLOSED.) SHE CLRED US FOR THE APCH. DURING THE CONVERSATION WITH CENTER; I SEEM TO RECALL THE CTLR MENTION THE WX 'HAD CHANGED.' I DIDN'T MAKE AN INQUIRY AND SHE DIDN'T GIVE US ANY WX BUT CLRED US FOR APCH AFTER ASKING IF THE WX WE HAD WAS BELOW OUR MINS. WE LANDED WITH WHAT WE ESTIMATED PRESCRIBED VISIBILITY. 5 MINS LATER; TWR OPENED AND CALLED THE WX 500 AND 1/4 IN FOG. MY CONCERN IS THAT WE WERE 135 AND WERE LEGAL TO START THE APCH BASED ON COMPANY WX (300 AND 3/4); BUT THAT THE 'CHANGED' WX MAY HAVE BEEN LESS (ALTHOUGH NOT GIVEN TO US) AND THAT WE MAY BE CHALLENGED BASED ON OFFICIAL WX BEING 1/4 MI AFTER WE LANDED. THE WX WAS UP AND DOWN. WE RPTED 3/4 MI VISIBILITY DOWN RWY ON TKOF (10 MINS AFTER TWR CALLED IT 1/4 MI). MY POINT IS THAT IF CENTER HAD NEW WX (LESS THAN 3/4 COMPANY GAVE US); THEN CENTER SHOULD HAVE GIVEN IT TO US. IF IT WAS LESS THAN 3/4; WE WOULDN'T HAVE STARTED THE APCH; WHICH I'M AFRAID MAY BE CHALLENGED.