I think I'd prefer to cast lighning bolt over fireball for thematic reasons. Is there a way to shape the way the spell moves? Say alter it's course 90 degrees at one point?
I don't know of a way to do it with lightning bolt, but if there's a targeted spell that otherwise suits your needs then you probably want Seeking Spell.
I'm interested to see if anyone finds something that does this. I can't even find something in 3.x that does it. Closest is Sculpt spell which turns you bolt into a ball or Bend Spell which eliminates cover, but neither do what you want.