When I taught weather with Key Stage 3 pupils, I used to use a Met Office pack which had some outline maps of the UK, and some reusable stickers with weather symbols on. It's still available for sale from the MET OFFICE shop for £15.
Students could be video/audio recorded standing in front of the board, to which the map was 'blue-tac'ed (is that a word ?)
Some colleagues used a 'green screen' setting on their camcorder and a tarpaulin from B&Q to rig up a more professional studio style effect.
Noel Jenkins produced a neat web based solution on his Juicy Geography website.
I tried it out and it's a really neat tool that I'm sure I would use if teaching about weather forecasting and the way that the information is collated and presented.
Symbols are dragged onto the UK map, which can be re-sized and positioned accordingly, as in the example above. A large range of symbols is included, and they are satisfyingly large and clear. A LOGO can also be added e.g. a school crest or departmental 'logo' of some kind.
Once this has happened, pressing a button marked PRESENT THE FORECAST will start a Google Earth tour which mimics the slow pan across the country in various directions that the BBC uses in their forecast...