Possible to combine fast moving clouds with normal lower frame?

Just curious if its possible to have a city scene (or any other scene) with fast moving clouds and normal moving lower frame.

I shot some 30 min clips of clouds over Potomac river in Georgetown waterfront, and when played back faster in FCPX it looks like timelaps, but the kayakers and boats move very fast too.... which I would like to slow down to normal speed in the same frame.....

If you have a blue sky in the 'normal' speed clip, I suppose you could try chroma keying the 'fast' speed clouds into the 'normal' speed clip. Not sure how well that would work. Or if the camera is stationary in the 'normal' speed clip, you could try masking out the sky and insert the new 'fast' speed clouds.

Could you post maybe 10-20 seconds of each clip so we can give it a try and let you know better?

Al

sounds like something you would do in aftereffects.

i think you would have to mask it. but heres the thing if you have equal amount of footage of both halves. then if you are speeding up on half and wanting the other to be normal speed then you need a butt load of extra footage of clouds to compensate other wise it will start repeating or run out. might not be able to notice clouds repeating if you have enough footage.

im like 99% sure trying to chroma key that would be a challenge.

Thanks for your response, Chopper, Brian.
Although, at this time your response/suggestion is beyond my skill level, it gives me a direction to research and I am happy to learn that its possible...

I will post a few mins downloadable link tomorrow for you to try out what you suggested.

Thanks a ton for your replies.