Haven't seen this posted here and I'm quite surprised. The weather.im service is NWSChat for those that don't have NWSChat access.
To access, all users can go to
http://weather.im/live and either register a new account or log in. You can also do an anonymous login but you won't be able to save anything.
Real-time products from the Weather Forecast Offices are displayed on the monitor on this website. You can join a specific WFO chat room by joining WFOchat (for example - BMX out of Birmingham would be bmxchat)
I have my own group chat room on the server, awpwxchat. Feel free to join in!