Didn't the old graphics simply have a gradient fade in the same spot so that the cut-off was less noticeable?
The cloud overlay does appear in full with the MeteroGroup graphics when doing the forecast for something like more than 48 hours in the future, so it could just be a case that the more-accurate weather modelling stops at that cut-off point when doing the coming day etc, and there's less of an effort to cover it up than before? I agree that it doesn't look fantastic, although on the whole the graphics have certainly grown on me since their launch.
The old graphics had no cloud overlay - merely darker shading on the map - similar to ITV now - which made it much easier to see what was going on and where the cloud actually was. Now, it is extremely difficult to judge cloud from snow from fog from ice/frost. I thought by now that the BBC would have been removing elements from their map such as the cloud overlay to make it more understandable, rather than adding to them by sticking "Liverpool" on the map.
I agree, the vertical line cut off of the cloud overlay by the weather presenter does look poor.