Target AoE or Instant AoE?
Just pick units around the point and order dummy caster to cast storm bolt (change the effect of stun) or use any other disable ability...
okay listen, you want it to be like when you CLICK on the spell you see a circle (like using flamestrike) or see a point wich makes an area of effect (like using frostnova) or you want it to be used instantly freezing everything near the caster (like using war stomp) tell me so i can gladly help you
It only leaks the unit variable and the terrain effect.
You can solve that using a group and pausing the units. or just setting their speed to 0 and adquisition range to 0
That will solve the terrain effect leak and for the units just set the variable = no unit.
Hope i helped.