Once networked the clients normally just reflect whatever weather is on the server...if you change any weather parameter on the server you can see the change happen immediately on each client.
To clarify I am also running Xplane on the server but don't use it for a scenery display. It is the Xplane server and it gets FSGRW weather, which is delivered to the clients, just like the aircraft position, speed, altitude data etc.
Haven't had any issues running this way until SMP 3.1 and RWC. I intend to wait for the 3.1 fix mentioned above before making any further tests of RWC with my configuration.