MISTAKE IN WT AND BAL CALCULATIONS NOT CAUGHT UNTIL AFTER TKOF.

Narrative

ON PREFLT FOR FLT WITH LEG FROM ORD TO MSP; I; AS THE SO; MADE A MISTAKE IN THE WT AND BAL VERIFICATION BEFORE PUSHBACK. OUR RELEASE FUEL FOR THIS LEG WAS 31000 LBS. THE WT AND BAL REFLECTED 25000 LBS AND I DID NOT CATCH IT; NOR DID THE 2 RAMP AGENTS WHO SIGNED THE WT AND BAL BEFORE I REVIEWED IT; OR THE CAPT WHO SIGNED IT AFTER I REVIEWED IT. THE CONTRIBUTING FACTORS TO THIS EVENT WOULD INCLUDE: RAINY AND WINDY WX AT ORD; BACK SIDE OF THE CLOCK SCHEDULE WITHOUT HAVING SLEPT DURING THE DAY; THE RAMP PERSONNEL CONFIRMING 3 TIMES THAT THE FUEL SHOULD BE 31000 LBS. THE RAMP AGENT DISCUSSING AN INCREASE IN THE '0' FUEL WT. 2 MINS PRIOR TO DELIVERING THE WT AND BAL TO ME; DISTRS WITH LOADING CREW TO MOP UP PUDDLES IN THE ENTRY WAY AND COCKPIT FROM THE RAIN; AN INCREASE IN PAYLOAD THAT DIFFERED FROM THE FLT RELEASE PROJECTION; AND THIS RESULTED IN APPROX THE SAME TKOF GROSS WT (13500 LBS) WHICH WE HAD EXPECTED; PRESSURE TO EXPEDITE FOR ON- TIME PUSHBACK. RESULT: OUR WT AND BAL SHOWED A TKOF GROSS WT OF APPROX 13400 LBS INSTEAD OF ACTUAL 14100 LBS. I DISCOVERED ERROR IN PREPARATION FOR LNDG CALCULATIONS AT MSP. I DISCUSSED IT IMMEDIATELY WITH THE CAPT. HE DISCUSSED WITH COMPANY SAFETY DEPT ON ARR AT MSP. CORRECTIVE ACTION IS; AS ALWAYS; PAY SPECIFIC ATTN TO DETAILS. NO OTHER PROBS OCCURRED ON THIS FLT. SUPPLEMENTAL INFORMATION FROM ACN 251687: AS ALL 3 FLC MEMBERS AND 2 RAMP AGENTS ALL MISSED THE DISCREPANCY; I CAN OFFER NO DEFINITIVE ANSWER AS TO WHY. OBVIOUSLY; THE ULTIMATE RESPONSIBILITY RESTS WITH ME; AND I SOMEHOW FLUBBED UP AND MISSED IT! WE HAD TO LEAVE LGB FOR ORD AT XA30 LCL; AND FLY ALL NIGHT TO MSP VIA ORD. THE CHANGE IN FLT TIME (DAY VERSUS NIGHT) AND BODY CYCLE ALSO; I FEEL; CONTRIBUTED. ALSO; SINCE WE CAUGHT A SIMILAR ERROR AT LGB; I FEEL LIKE THE RAMP AGENT SHOULD ALSO BE REQUIRED TO VISUALLY/VERBALLY ASCERTAIN FOR HIMSELF THE ACTUAL FUEL ON BOARD BEFORE ENTERING THE AMOUNT INTO THE COMPUTER TO GENERATE THE WT AND BAL. MISTAKES HAPPEN. THIS ONE WAS MINOR. BUT IT IS AN IMPORTANT LESSON FOR DOUBLE-/TRIPLE-CHKING ONESELF DURING ALL PHASES OF OPS; PARTICULARLY IN THOSE WHERE FATIGUE; BACK SIDE OF THE CLOCK; AND SUCH FACTORS ARE PRESENT. IF NOT ACCOMPLISHED; AS EVIDENCED BY THIS OCCURRENCE; ERRORS CAN FALL THROUGH THE CRACKS; NO MATTER HOW MANY CHKS AND BALS ARE APPLIED.