12z GFS ens looking better down here for cold post Xmas, although still showing high confidence in mild for Christmas Day, Boxing Day a little more uncertain, likely to start mild but may cool down during the day if GFS is right. Hopefully ECM ens will continue from where the 00z set left off and firm up the colder cluster.

Mogreps don't look great for Manchester or Carlisle either.  Very uncertain for sure. 

 ECM opp was a colder outliner Dave, I’d like to look at the clusters we will have to wait and see.

https://www.theweatheroutlook.com/twodata/ecmwfens.aspx?run=12&lg=850&lglocation=london

Its like a Christmas Pantomime with several of the main characters still to appear. But then again, with a week to go, there are several Acts still to come. “He’s behind you!, oh no he isn’t, oh yes he is!”

That wintry spell was significant for me because in my lifetime virtually all protracted cold spells later in winter have been preceded by at least one potent even if short cold snap before Christmas. This even applied to 1947 (just before my lifetime!). Of course a cold snap before Christmas does not necessarily mean the latter cold spell will materialise.

ECM ens not too dissimilar to GFS for me - there's a smaller colder cluster for Xmas Day but majority go mild before a noticeable cool down at some point during Boxing Day. That leads to 3-4 days with decent cold grouping (albeit not that cold), which is now the majority option although there's still some stragglers. After that there's a signal for temps to recover to above average for the New Year. 

Will need to see 2-3 days of consistency but good signs  today for a countrywide chilly/cold spell - Scotland more likely to see several days of notably below average weather, for MBY currently more likely it'll be 3-4 days (take your pick for those in between).

I guess word of caution being a lot of the runs are wobbling around the kind of 850's that bring temps of 2-3c at the surface for me, which is cold but with winds being from a NE quadrant may not be cold enough in any convective stuff. Little bit early for looking at that of course, with it more important the general pattern sets up and things don't readjust further North again (The 850s are probably good enough during frontal snowfall of course, definitely so if any approaching lows pick up some low DPs from the continent). 

ECMWF 14-day ensemble weather forecast for Royal Tunbridge Wells | Weather.us

As a few folks have mentioned once or twice it's infinitely better than what we've had at this time of year for most of the past several years

Took so long drafting the follow up didn't see you'd posted 

Overall that's a reasonable set for the post Xmas Day period. Slowly getting there

The operational run or the entire ensemble set?

ECMWF op was on the lower end of the ensembles here too, but once again within a substantial cluster:

But spread is wide after Christmas Day. 

It's a FI kitten compared to the snarling tiger that was Christmas time 1978.

Certainly the opp at least, but expect the ensembles to shift with the opp runs a bit more now

That ECM was a cold outlier (certainly for the south).

https://www.ecmwf.int/en/forecasts/charts/web/classical_meteogram?facets=undefined&time=2021121812,0,2021121812&epsgram=classical_10d&lat=51.57&lon=-0.83&station_name=Reading,%20United%20Kingdom&altitude=undefined

Yeah I don't remember 1978 but from the reanalysis charts there does seem to be some similarities with some of the model output at the moment.

I make that lower quartile, not an outlier?

Similar trend to here. Also similar in that Op gets much cooler much quicker than the main cluster out to day 10. 

More runs needed. 

Snow heading South Boxing Day morning 

Very interesting Boxing Day 

100% Imbyism here 

Be buried if this came off