https://modeles16.meteociel.fr/modeles/gens/runs/2024121600/gensnh-31-5-384.png 

Look here. This is a 384 ensemble mean Z500 anom chart. Its rare to see anything but the weakest of colours on these charts, yet we have a suggestion that most ensembles are going for higher than average heights over Greenland and the NW atlantic. The models have been suggesting this for several days now.

I think we might want to accept a cold spell over xmas is unlikely, but things are about as confident as its possible for them to get (which tbf is still not very confident) that fortunes could change before the new year.

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/EMON_BC.png 

Also suggesting a better pattern after xmas.

Agree a mostly favoured outcome a quiet settled spell of frosts before the storms return

It's never been 'the norm' for a prolonged period in recorded British history. Yes, there've been clusters of 'much more likely', but it's never been the norm. 

But it's symbolism, innit?

I think many people have a mental picture of the ideal Xmas - and almost all will have a rural/village snowy scene as part of it.

We haven't had many  wintry showers in recent years with white Northern hills.  Maybe that is the future now.  There was a North Atlantic cold pool for a few years 2015-2020ish, which might have masked how bad things have become from zonality. 

Not really.

The start of the 19th Century was the back-end of the LIA - and the 1810's were a very cold decade, with several white Xmases. There were, of course, a number of major volcanic eruptions around that decade (including Tambora, a VEI7, which led to 'the year without a summer'). But for most of the rest of the century, a white Xmas - at least in London - was pretty much as rare as now. Things did uptick in the last couple of decades, with a white Xmas slightly more likely than not.

Worth noting that Dickens was a child in the 1810's, and many have noted how this could have influenced his notion of Xmas weather. Yet the year that A Christmas Carol was first published, London reached 10.1c on Xmas Day. 

I've searched unsuccessfully for a simple list of all white Xmases since 1800, which would have made it simpler. But after reading a number of articles, a very rough estimate of the ratio of white Xmases - and I'm talking falling and lying snow in London - in the 19th century would be around 1-in-4 to 1-in-5 (and concentrated in the first two and last two decades on the century). So not 'the norm' - but much more common than now

The last picture-postcard White Christmas in London would, like here, have been in 1970, I believe. So that's currently at best a 1-in-55 year event, as we (sadly) won't be breaking that streak this year either...

I don’t think the problem is the jet stream being more active (‘the Atlantic’), it’s the northward displacement of the high pressure belt that sits to our south. Brian has posted the graph that shows the slow but clear uptick in pressure to our south over recent decades. The only possible consequence of that is an increase in the probability of winds from the south to west. With the North Atlantic being almost constantly anomalously warm due to global warming that just accentuates the warmth and increased potential for heavier rainfall.

The Azores High moving north *could* be a bonus... if it stays mid-Atlantic and brings us a northerly flow (in winter that is... in summer I want it vacationing NE'wards to sit over the UK ;))

A quick zip through the postage stamps for Xmas Day shows high pressure to our south, over France or slightly east, accounts for about 70% of the ensemble members, and high pressure somewhere between the Azores and France accounts for the rest. Temperatures predominantly average to mild, with a handful of slightly cooler options where the high pressure has more influence in the south.

It still wasn't "the norm". I'm sure I remember reading somewhere that Charles Dickens was to blame for popularising the idea of snow at Christmas, and he was influenced by a particular year in his own childhood.

Edit: just looked it up and apparently there was a White Christmas in 1830, when Dickens was 18. Also 1836, the year The Pickwick Papers was being serialised.

Alos realised I had missed Saint say much the same thing. Oops!

I'm not sure I would agree with Q's assertion the the Atlantic has become more active over the last few decades. If anything, it is less active than it used to be, and an active Atlantic at this time of year would be spurred on by the net cold over warm Tm's one time would be swiftly spun out of existence in quick and often violent fashion. Now, there is just too much warm tropical air for the cold, Arctic air to 'fight off'. Still happens closer to the Arctic circle on occasion, but how long before even that gives up the fight? 

12c 850s on Christmas day is remarkable and a testament to how far GW has already gone. 

Yes, it’s slightly cooler at the surface: a range of 8-11c at midday for most of the UK.

Markedly cooler on Boxing Day and 27th

Those temperature charts also show quite cold air over Scotland. Okay, we know that we're not going to see a Beast from the East for Christmas Day but much of Scotland will see cold and with not too great a change, it's possible that we could find the colder air coming further South to affect more of us.

Our climate really is pitifully crap in winter. 

It is but you know full well it could change.  You also know, that sinking feeling is most likely justified.