I would remember people that very often the first attempt fails or brings only a transient cold spell. What we have beyond the initial northerly incursion is an even stronger mid atlantic ridge and a canadian high separated by a weak trough. The GFS has been consistantly merging these together in low res. Exactly how this pans out for the UK varies considerbly, however the general pattern is for a greenland high to eventually establish even if it is a very gradual process.
To illustrate, I annotated below (I hope mods are okay with this, I have scaled it down, and it is annotated)
The models consistantly try to merge the two dominant anticyclones, and they are converging at greenland. Also the arctic high is moving in a favouble direction too.
Originally Posted by: Quantum