I think we need consistency for at least  another couple of days before concerned about such a scenario. Cool or cold and unsettled after a milder few days would still be the summary despite the 18z GFS eye candy.

 at the surface post 144 even for the south very cold run 

night min-10 under snow cover?

http://www.meteociel.fr/modeles/gfs/royaume-uni/temperatures-2m/156h.htm

agreed but on and off for a week the signs have been there and Sod's law the government is having a tough time!!

Looking at these charts, the Decembers of 2010, 2009 (from about the 19th onwards) and 1981 spring to mind.

As Michael rightly says though, we need to see these runs on a consistent basis before we can become anything even approaching reasonably sure wrt what they show coming to pass.

Well in all my many years looking at model runs I can't recall seeing anything like that 18z. In FI we have a low running down the West side of the UK from Greenland to lie to our SW, which then deepens and moves NE towards us drawing in Northeasterlies with the Greenland High building towards the Siberian High. Is that possible?

It will be gone in the 00z but wow, a run to remember.

Edit - interestingly the 18z ends producing the -ve ao whiich Ian Fergusson referred to in his tweet earlier for the 2nd half of December.

The pub run living up to its reputation. Insane charts which would see the SE buried. 

Let’s see if it’s still there in the morning.

Tonight's EC15 refusing to let go of the idea of cold troughing over the North Sea region post day 10, and still showing a high degree of uncertainty as to general synoptic pattern of the N. Atlantic. In sum: cool mP type weather seems to want to hang around until mid-month. 

Some really nasty/amazing charts amongst the GEFS

This is P4

http://www.wetterzentrale.de/maps/GFSP04EU18_150_1.png

http://www.wetterzentrale.de/maps/GFSP04EU18_150_2.png

The "mean" precipitation chart at 156 hours has heavy snow over most of the country. In fact looking at the mean charts on Meteociel I think the 18Z ensemble is a fair bit colder than the 12Z

12z ECM ens

http://www.weathercast.co.uk/meteo/eps/ensemble-tt6-london.gif

Fairly chilly. 

As if something clicked and the confusion has lifted.

decent snow opportunities there up to 50% for London

Very similar to GFS 18z in terms of the signal for the very marked temperature drop next Thursday.

The strong clustering for continuing cold is still there.

The precipitation spike on the op on Day 10 shows over 15mm. Not sure if it's cold enough for snow (850s around -4C, 500-1,000 thickness in the high 520s) but if that is snow......

http://www.weathercast.co.uk/meteo/eps/ensemble-rrrcum-london.gif

Marginal snowfall and could be legendary!

I think some people, certainly on the other side, are getting carried away with some unlikely synoptics. The new Meto update goes for a toppler, with rain and wind returning quickly from the NW and I would think by the 12zs tomorrow there will be good agreement on that.

That’s what the current MetO forecast says but it hasn’t updated yet and doesn’t reflect the latest output.  That output doesn’t indicate that what you’re suggesting is anything but a low probability; and that’s what I’d expect to see in the next update.

Indeed

Once again we build ourselves up for the inevitable fall

We've been here so many times, but people want to believe it so get carried away. It could be a bloodbath and many broken prams on netweather tomorrow

you two sound like the chuckle brothers amusing the first time then me to you......yawn