You are, of course, absolutely correct about the FA's - they can't see what the aircraft is headed toward and thus have no idea what's coming until they get a call from the cockpit or feel turbulance.

Tecnically, you're basically correct about the pilots - they can't see turbulance since it's nothing but the air currents moving up in down in relatively rapid succession - like a boat speeding across choppy water, the verticle movements of the airstream causes a bumpy ride - except you can see the water. So seeing turbulance is like seeing wind - impossible for mere mortals.

However, like deducing the existence of wind by it's effects or conditions that usually cause winds, the pilot's can often see areas where turbulance exists by looking at the clouds - they can cause turbulence and/or show the effects of turbulence.

When I retired, some of the radar manufacturers were testing radar that could "see" turbulance, at least in moist air like clouds and rain. they did it by measuring the movement of water droplets with doppler radar. A fancy way of doing basically what pilots do except doppler works when the plane is in clouds and the pilots can't see 10 ft in front of the plane.

Finally, though it's neither seeing or deducing the presence of turbulance there's good old ATC. Pilots are pretty good about reporting turbulance encounters to ATC, and ATC is good about passing those reports on to flights that will be flying through that same area.

Jim