LTT LOST DIRECTIONAL CTL DURING TKOF ROLL AND LEFT THE RWY BEFORE BECOMING AIRBORNE.

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IT WAS THE F/O'S LEG TO FLY. THE TWR CLRED US INTO POS AND HOLD RWY 35. THE F/O TAXIED ONTO THE RWY WHILE I COMPLETED THE FINAL ITEMS OF THE BEFORE TKOF CHK. I NOTICED AN LGT ON SHORT FINAL TO RWY 27R AND IMMEDIATELY BECAME CONCERNED ABOUT POSSIBLE WAKE TURB AT THE INTXNS OF RWY 35 AND 27R. AS SOON AS THE LGT WAS THROUGH THE INTXN OF RWY 35 THE TWR CLRED US FOR TKOF WITH NO MENTION OF POSSIBLE TURB FROM THE LGT. IT APPEARED THAT THE LGT HAD T/D'ED JUST PRIOR TO THE INTXN OF RWY 35 SO I WAS MORE CONCERNED ABOUT JET BLAST THAN WITH WAKE AT THAT POINT. I TOLD THE F/O TO WAIT A FEW MOMENTS BEFORE STARTING TO ROLL TO AVOID ANY TURB. AFTER WAITING WHAT WE THOUGHT WAS A SUFFICIENT PERIOD OF TIME THE F/O STARTED THE TKOF. THE INITIAL PORTION OF THE TKOF ROLL SEEMED NORMAL; HOWEVER SOON AFTER THE ACFT SHOOK LIKE WE HAD HIT A GUST AND SEEMED TO BECOME MOMENTARILY AIRBORNE. AT THE TIME; I WAS MOMENTARILY HEADS DOWN MONITORING THE PWR AND THE GAUGES AND MAKING THE APPROPRIATE CALLOUTS. AFTER FEELING THE GUST; I LOOKED UP TO FIND WE WERE HDG OFF THE LEFT SIDE OF THE RWY. THE AIRSPD WAS APCHING V1 AND I TOLD THE F/O TO ROTATE; AND I ALSO APPLIED SOME BACK ELEVATOR PRESSURE. WE BECAME AIRBORNE AND ACCELERATED TO V2 AND PROCEEDED WITH A NORMAL CLB. AT THAT POINT NEITHER I NOR THE F/O THOUGHT THAT THE GEAR HAD GONE OFF THE RWY INTO THE GRASS AND THERE WERE NO ABNORMAL INDICATIONS IN THE ACFT. WE PROCEEDED UNEVENTFULLY TO OUR DEST AND MADE A THOROUGH POST-FLT INSPECTION AND FOUND NO DAMAGE TO THE ACFT; BUT DID FIND SOME GRASS IN THE LEFT WHEELS. WE NOTIFIED COMPANY OF THE SITUATION IMMEDIATELY AND THEY HAD MAINT LOOK AT THE ACFT--NO DAMAGE WAS FOUND. IN MY OPINION; THE CONTRIBUTING FACTORS TO THIS OCCURRENCE WERE LGT TURB; A WET RWY; A XWIND FROM THE LEFT AT 12 KTS; AND VERY POOR RWY CENTERLINE MARKING.