MD82 FLC DIVERTED DUE TO LOW FUEL.

Narrative

APPROX 10 MINS BEFORE DEP; THE CAPT AND I WERE ABLE TO TAKE OUR SEATS. I REVIEWED THE FUEL SLIP; WHICH SHOWED THAT WE WERE PLANNING ON A FUEL LOAD OF 20300 LBS OF FUEL FOR OUR FLT TO STL. THE PRELIMINARY WT SLIP ALSO SHOWED THIS AMOUNT. THE COCKPIT FUEL GAUGES; PLUS THE FUEL SLIP SHOWED 20300 LBS. A QUICK MENTAL COMPUTATION FOR AN APPROX 2 HR FLT AND FAA RESERVES AND TAXI; SHOWED THAT TO BE ADEQUATE FUEL. THE CAPT SAID THE WX IN STL WAS 'GOOD.' IN THE BACK OF MY MIND THOUGH; I THOUGHT IT WAS A LITTLE ODD THAT WE WERE ARRIVING AT STL WITH ONLY FAA RESERVES. ENRTE TO STL; WE GOT A RERTE FOR WX. THE RERTE TOOK US CONSIDERABLY NW AND THEN S INTO STL. I MENTIONED TO THE CAPT THAT I COULDN'T BELIEVE DISPATCH HAD RELEASED US WITHOUT ADDITIONAL FUEL; SINCE THEY SHOULD HAVE KNOWN ABOUT THE ENRTE WX (IE; LNDG WITH 4500 LBS (FAA RESERVES)). HE SAID NO; WE ARE LNDG WITH 9000 LBS. I THEN ASKED HOW WE COULD POSSIBLY DO THAT; CONSIDERING OUR PRESENT FUEL. IT WAS THEN THAT HE DISCOVERED THAT WE WERE FUELED 4500 LBS LESS THAN THE DISPATCH RELEASE. AS A RESULT WE ELECTED TO LAND AT MLI FOR FUEL RATHER THAN LAND AT STL WITH APPROX 3000 LBS.