This is an interesting situation and I'd like to try to figure it out but it's above my pay grade.

On March 4, since we could not get flights together, two of us took separate flights from Florida to Chicago as follows:
AA2317 RSW-ORD, departed late by almost 2 hours at 1:45pm.
AA1476 PBI-ORD, departed at about 3pm.

My friend on the first flight from RSW told me that it was completely smooth, no turbulence, but the flight from PBI hit some pretty big bumps from Kentucky onward and the flight attendants had to remain seated for the last hour of the flight.

I'm trying to understand how or why that is possible since we both traveled about the same route within about an hour of each other.

Did the turbulence occur only after the first flight ? The rain/sleet/snow storm was ongoing at all times that day all across the Midwest.
Did the planes take different routes or fly at substantially different altitudes?
Or does turbulence form or move quickly, or simply occur in small areas?
Last thought: perhaps my friend and I have totally different perceptions of "turbulence" !!

Thanks for any input !