BBC weather maps are clear and crisp. They also rate highly IMHO for using well chosen colors e.g: blue indicates frost and subtle blobs of white illustrate snow fall (on the forecast film clip only, not in the screen shot above). Where they don't do so well is thinking how these elements work together on the map. In the screen shot above we have a number of competing shades of blue all ilustrating different things:
A] Sea covered with cloud
B] Sea with clear skies
E] Background to a Temperature label (Deg C)
Poor Layer Coloring: They have 6 layers on one map plotted as different shades of blue! The map could be improved by replacing blue shading with the use of symbols, interestingly, this is how they BBC used to do it a few years ago (see above).
I've criticised the BBC for overcomplicating maps of elections here.