FLT CREW OF A320 FAIL TO REALIZE THAT THE TOTAL OF SEVERAL INCREMENTAL INCREASES IN ACFT TKOF GROSS WT EXCEEDED THE MAX ALLOWABLE WITHOUT DISPATCH CONSULTATION.

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DURING PREFLT PLANNING; OUR 'FPF' SHOWED A TKOF GROSS WT OF 157.8 LBS WITH A ZERO FUEL WT OF 121.5 LBS. I ADDED 700 LBS OF FUEL FOR EITHER ENRTE WX DEVS OR THE ANTICIPATED LONG TAXI OUT FROM PHL. AT THE ACFT; WE PULLED UP (FROM ACARS) A PLANNED WT MANIFEST WHICH NOW SHOWED AN INCREASED ZERO FUEL WT OF 122.8. THIS WOULD NOT HAVE TRIGGERED A REQUIREMENT TO CONTACT DISPATCH. WE ALSO PULLED UP RWY DATA; WHICH WAS BASED ON THE NEW ZERO FUEL WT AND FUEL. AFTER PUSHBACK; WE RECEIVED FINAL WTS WHICH SHOWED A FURTHER INCREASED ZERO FUEL WT OF 124.3. THIS REQUIRED NEW RWY DATA SINCE THE NEW TKOF GROSS WT WAS SLIGHTLY ABOVE THE ASMD ATOG THAT WE HAD PULLED UP. HOWEVER; IT WAS ONLY A FEW HUNDRED LBS ABOVE AND ASMD ATOG; AND THUS THIS DIDN'T 'TRIGGER;' IN MY MIND; THE NEED TO CONTACT DISPATCH DUE TO THE WT INCREASE. AFTER TKOF; WE NOTICED THAT WE WERE 'DOWN' ON THE FUEL SCORE ABOUT 800 LBS. WE BEGAN TO INVESTIGATE WHY; AND DETERMINED THAT OUR FINAL TKOF WT OF 161.3 LBS WAS 3.5 KLB HIGHER THAN OUR ORIGINAL 'FPF' WT OF 157.8 LBS. WE CONTACTED DISPATCH TO ADVISE THEM OF THE SIT. THE DISPATCHER CONFIRMED THAT WE WERE STILL OK FOR METHOD #1 DRIFTDOWN; AND THAT OUR FUEL MET ALL FAR REQUIREMENTS. WE CONTINUED TO SFO UNEVENTFULLY. I THINK SEVERAL ITEMS CONTRIBUTED TO THIS EVENT. FIRST; EACH OF THE WT INCREASES WAS SMALL. IT WAS ONLY THEIR CUMULATIVE EFFECT THAT CAUSED US TO EXCEED THE FOM GUIDANCE FOR WT INCREASES THAT REQUIRE DISPATCH NOTIFICATION. THUS; THE PROB DEVELOPED INSIDIOUSLY. SECOND; USE OF ACARS WTS INSTEAD OF A PLANNED WT MANIFEST TENDED TO OBSCURE THE WT INCREASE THAT OCCURRED BTWN FLT PLANNING AND OBTAINING ACARS RWY DATA. THE ONLY DOCUMENT IN THE COCKPIT THAT SHOWED THE 'ORIGINAL' PLANNED TKOF GROSS WT WAS THE 'FPF.' ALL OTHER DOCUMENTS SHOWED THE PLANNED WT AT LATER POINTS IN TIME. THIRD; THE FINAL WTS ARRIVED WHILE WE WERE DISTR WITH TAXI INSTRUCTIONS FROM PHL GND. THIS CONTRIBUTED IN OUR FAILURE TO NOTICE THE EXTENT OF THE INCREASE IN THE FINAL ZERO FUEL WT. SUPPLEMENTAL INFO FROM ACN 668951: FAILED TO CALL DISPATCHER WHEN FINAL WTS GREATER THAN +2000 LBS ABOVE PLANNED GROSS WT.