I guess that with all this snow predicted over the next few days then the M4 traffic cam network will be working overtime.
If you want to have a quick look at traffic and snow conditions on the M4 motorway over the next few days then there is a good summary page for South East Wales with links to individual M4 webcams to be found on the BBC here – http://www.bbc.co.uk/travelnews/southeastwales/trafficcameras
A similar traffic cam page for South West Wales can be found here – http://www.bbc.co.uk/travelnews/southwestwales/trafficcameras
The BBC also has a good summary page on the current situation on the national motorway network here – http://www.bbc.co.uk/travelnews/local/motorways.shtml.
There is also a local page listing all road closures and holdups in South East Wales here – http://www.bbc.co.uk/travelnews/southeastwales
Update: Thursday 16th December 2010 – you may find this new page useful – http://www.south-wales.org/2010/useful-information-for-south-wales-snow/
M25 photo above Copyright: Andrew Dixon, http://www.flickr.com/photos/andrew74/ with thanks.