A similar story from the ECM 00z ensembles for London.  The effect of the introduction of a shot of Arctic air shows up starkly: even an ice-day, remarkably. The op was in the colder cluster but not unsupported. 

The other point to highlight is the continued build of a cluster suggesting a persistence of the colder conditions becoming a little more likely.  The wall-to-wall very mild conditions being predicted so confidently by a few posters only a week ago seem to be disappearing with each run.

Doesn’t count - March is a Spring month 😂😉

....not until the 21st.....I'll get my coat

According to the Met Office the average max for Heathrow in Dec is 8.3C. See: https://www.metoffice.gov.uk/research/climate/maps-and-data/uk-climate-averages/gcpsvg3nc Presumably it's a fraction lower at this end of the month so around 8.1C to 8.2C. Today temps have reached 9.5C at least, so that's over 1C above the average however it is sliced and diced. Not very mild but in the mild category. There is some variability in southern counties with temperatures ranging from ~8C to 11C. 

LOL, I had the same thought.  I really do like that summer weather you get on September 20th.....

Silence speaks volumes! ha! Crazy to think the coldest ensemble for Oslo, Norway is -12c or -13c @ 850hpa and even this is an outlier:

Could be mild for all parts and any cold air looks like it will topple over the ridge and go to Greece  -which look to be below average meanwhile take a look at how mild it will be in Oslo, Stockholm too?

Oslo

https://www.wetterzentrale.de/maps/GFSOPEU12_3_1.png

https://www.wetterzentrale.de/maps/GFSOPEU12_3_2.png

Interesting to look at the current “blowtorch” setup and compare it with actual reality. Based on some recent commentary I’d expect the above to result in 16C balmy temps across the country (I accept it has been very mild in northern Scotland)..

It has actually felt very average today here and feels relatively chilly outside at present. Currently 7C.

Always a good reminder that very high 850’s don’t always result in record breaking or exceptional surface temps in winter. 

P20 has it nailed 

https://www.wetterzentrale.de/maps/GFSP20EU12_372_1.png 

well I can’t disagree, January looks to be shaping up to be another bland effort. It will be interesting to see what the long range models suggest, but I am fearing the heart of this winter will be unceremoniously ripped away

According to the BBC "Temperatures reached 16.8C in northern Scotland overnight - the highest ever recorded for the UK this late in the year." (see https://www.bbc.co.uk/news/uk-50941114) If the current blowtorch set-up persists for much of January I would expect several more opportunities for anomalously high temperatures to be recorded in the UK. Perhaps more importantly is the chance of this winter falling into the very mild category. However, there will be colder days sandwiched in even if pressure remains high to the south.

From what I read the other day both ECM and UKMO seasonal models/forecasts have western Europe in the UK as generally mild and unsettled with only transient cooler/cold shots.

That said if you look at the GFS ens they're generally settled and fairly cool for my neck of the woods so if that verifies and for this part of the country the seasonal model broad brush forecast won't have been particularly accurate/useful.

Yes. 

However as soon as high pressure builds across the country (even if the core of the high is to the south), you can often throw the 850 projections into the bin. 

Yes - remarkable temps for Scotland - temps of almost 17c by night in Scotland, did temps rise to 17c? Or stick at that Temp? .

As for the HP yes should be cold at surface so hopefully something seasonal at night with frost maybe.

No

Just when you thought it couldn’t get much worse the threat of some stagnant easterly muck shows up. Thankfully it passes quickly on this run. 

Ensembles say it all currently. Quite dry with warm uppers for the most part with little disagreement, even in FI.

Looks a bit late 80's style at the moment. 

Freezing fog right down to the coast.. very seasonal 

GFS0z op has unrelenting HP close to the UK, mostly centred to the SW so calm in the S, windy in the N. Denmark and Germany affected by strong northerlies from time to time as LP develops over the Baltic, but the UK on the fringe of this, only on Mon 13th does a northerly briefly affect the east coast. ECM has the HP a bit further south so conditions generally more windy with emphasis on westerlies.

My guess is that the HP is likely to deliver mild cloudy weather except where the atmosphere is stirred up by passing LP so hope ECM is more accurate and generates some sunshine.

GEFS shows consistent dip in temp around 4th, to below zero in many places , followed by a strong rebound by the 8th to well above normal. Thereafter the runs diverge but temps decline generally with the op leading the way. Dry everywhere except the north.