I agree with this: if my 30' speed represents the distance I have time to move in a 6-sec narrative slice, and my jump distance is 20' and the game says by rule I can sequence my movement and actions in any order (barring action-specified dependencies) and the rules contain no penalties for doing my actions midair...
Then why not run 20', jump, travel 10' in air, fire off a spell, then we narratively leave me... hanging! and find out where I land when the spotlight's come back 'round?