The GFS and UKMO models diverge on the solution for this Friday. The GFS take a explosively deepening low from the southwest approaches, northeastward across central England and into the Skagerrak. The American model deepens the low from 997 to 967 hPa in 24 hours, and if this forecast comes off, this easily exceeds the 24 hPa in 24 hours classification for rapid cyclogenesis.
Meanwhile the latest forecast from the Met Office for Friday (which reasons for national security we can’t see in any detail) crucially doesn’t develop that same same low, and I guess keeps Wales and much of England in a broad warm sector for at least 24 hours. On the strength of this the Met Office have issued two yellow warning for heavy rain from anticipated large orographic totals across much of Wales and the Lake District. They are obviously very confident that this low won’t deepen like the GFS model expects, so confident in fact that they have issued warnings for Friday and Saturday more than 72 hours in advance. Personally I would have thought that they would have been better waiting till at least tomorrow or even Thursday before issuing any warning. They also neglect to mention in the details of their warning any risk of strong winds ahead of the low and in the warm sector during Friday. The Met Office model should be the one to trust on this occasion, but you never know every dog has its day.