Will this work to exchange water?

My cya is high and swim season is pretty much done. I wanted to do some water exchanges before closing. Its going to dump 5"+ of rain. If I have my solar cover on, pump not running, will the rain water lay on the top sevaral inches. If so would it make sense to waste the water through the bottom drain only to exchange it.

Dump the water before the rain comes and you don't have to worry about keeping the rain separate from the pool with the solar cover.