Baron 58/58TC
Flight Crew Multiengine; Flight Crew Private; Flight Crew Instrument
Flight Crew Last 90 Days 32; Flight Crew Total 1756; Flight Crew Type 856
Communication Breakdown; Confusion
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Human Factors; Weather; Aircraft
There were numerous thunderstorms in the area that had me concerned.  A strong cell had just passed and I had a good window to depart. However; I knew another TS [thunderstorm] cell was in my flight path.  On the most recent flight; my Garmin 530 did not have good XM Weather connectivity and I called Garmin; juggled the cell phone call; 'refreshing' the signal and verifying moving map weather was coming in. This was done on the ground but the plane has to be running and the Garmin 'on' in order to refresh the signal.I had previously filed an IFR flight plan; gotten a good weather briefing and contacted MBO ASOS.  I picked up my flight plan on the ground and was released.   However; a passenger had an urgent text/call and needed to leave a credit card at the ramp for his sister as promised.  I cancelled my release and taxied back to ramp; left the credit card and taxied to Runway 17.  I picked up my release again and was cleared for immediate departure with a 2 minute time off.I mistakenly said I was departing Runway 35 despite winds and my route to destination (137 degrees) favoring 17.  17 is also the no wind default runway.  I taxied to 17 and never had any intention of going north.  My mouth however said 35 and since JAN/class C personnel could not see me; this caused them an obvious concern. JAN is 8-10 miles south of MBO and operate 16/34 runways.   The JAN FAA controllers were courteous and voiced their concern but did not ask me to call upon landing.The thunderstorms; cell call refreshing; passenger drama; after a long week and lack of visual contact with a tower or ATC all played a part.  However; it's kind of like calling your kid by their siblings name... I know my kid but the right words wouldn't come out of my mouth.  I taxied to 17; winds favored 17; a departure on 35 would have required additional gymnastics to get on course...I knew I was on 17...but my mouth didn't say 17.I don't know how to prevent this from happening again short of a tower or digital camera at this airport or perhaps ATC giving a pilot a heading rather than (or in addition to) saying 'fly runway heading'.  I don't know if that would have made any difference but saying 'fly runway heading/350 degrees' might have alerted me to the fact that my intended direction of flight was not the same as ATC's understanding of it.
BE58 pilot experiences many distractions prior to departing MBO on an IFR flight plan with thunderstorms in the area. Pilot advises TRACON that Runway 35 will be used for departure; but he actually meant and used Runway 17.