HDG TRACK DEV DURING IAP ILS APCH CREATES NEED FOR PIC; PF; TO MAKE A 'MINI' SIDESTEP MANEUVER IN ORDER TO LAND HIS MLG. RPTR WAS FLYING A 'LOOSE' APCH AS WX WASN'T EXPECTED TO BE POOR AT ARPT.

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BOS ATIS RPTED 4000 FT BROKEN; 7 MI VISIBILITY; ILS TO RWY 4R. DID NOT FLY ILS PRECISELY EXPECTING VISUAL CONDITIONS EARLY IN THE APCH. AT 1500-2000 FT AGL; I ASKED THE FO TO ASK THE TWR CTLR WHAT THE CURRENT VISIBILITY WAS. THE TWR CTLR REPLIED; '7 MI.' WE FINALLY SAW THE APCH LIGHTS WELL OFF TO THE R JUST BEFORE REACHING ILS MINIMUMS. I MADE A QUICK JOG TO THE R; REALIGNED THE ACFT WITH THE RWY AND LANDED FIRMLY ON RWY 4R. A THICK FOG BANK WAS OVER THE WATER AND THE APCH LIGHTS BUT THE RWY AND ARPT WAS AS RPTED. OBVIOUSLY; THE FOG BANK WAS VISIBLE FROM THE TWR BUT WAS NOT RPTED. IF FOG BANK HAD BEEN RPTED I WOULD HAVE FLOWN THE ILS MORE PRECISELY. IN THE FUTURE I WILL BE MORE SUSPECT OF RPTED WX CONDITIONS (AND BE ESPECIALLY ALERT FOR FOG BANKS OVER BODIES OF WATER NEAR RWYS) AND I WILL EXECUTE A MISSED APCH WHEN DISPLACED THAT FAR FROM THE EXTENDED RWY CTRLINE. ALSO; OBSERVABLE WX PHENOMENA SUCH AS FOG BANKS SHOULD BE MENTIONED ON ATIS AND BY TWR/APCH CTLRS TO HELP PREVENT SIMILAR OCCURRENCES IN THE FUTURE.