The timespan from late FEB thru early to mid April is a golden opportunity for quality-sized river bass on the fly. If you wait until your comfortable (low clear flows and nicey nice wussy weather) in late April, it's too late!!! Your left with dink city.
If the big river bass are comfortable, your usually uncomfortable (higher and stained flows, etc.) but you will catch them. Don't wait until they are uncomfortable and the fair weather anglers are stomping all over the rivers-----your way too late.
The early bird may get the worm, but the early fly guy gets the hawg(s).