Yes, the key to getting snow with 850s of -5C or higher is either altitude, evaporative cooling, a low-level feed of cold air (as happens with continental easterlies down here) or a home-grown low-level cold pool, such as is formed over snowfields.

That said, with Sunday's battleground still looking like being over the Midlands, I won't be getting my hopes up of anything white from Sunday onwards. The best chance of snow in the south is, in my view, from showers on Friday and Saturday - albeit lower chance here in the far SE corner. At least there should be a frost on Sunday morning, under the weak ridge, before the rain moves in.

Gfs 00z flattening the pattern next week returning to our default mobile westerly regime 🙁

a definite trend to a warm up as we approach the Christmas holidays:

http://old.wetterzentrale.de/pics/MT8_London_ens.png

Not liking the look of the longer range charts this morning, with both ECM and GFS quickly collapsing the ridging in the Atlantic rather than building heights to the northeast. Hopefully not a trend that will continue!

For Sunday the latest fax chart has the low centred near Birmingham. http://www.meteociel.fr/modeles/ukmo2.php?carte=2000&ech=84

I agree. I looked at the ECM ensembles last night and towards the end there’s a very marked change with a lot of runs going mild. All the overnight runs have the same trend, with a large chunk of the polar vortex edging east from Canada (where we want it) towards Greenland (where we don’t). There’s also the weakening of upper heights.

Strmchaser did warn of this possibility last night. It could all change again but as it stands the longevity of the cold spell is in greater doubt this morning.

As for the short term, the risk of snow showers remains very high for favoured areas and even inland. The track of the slider seems to be firming up a little: as Retron says, the Midlands seems the southerly limit at the moment but perhaps the south Midlands.

We need the same rainfall twice a week for the next couple of months to get ground water supplies up. Not a pretty thought!

Back to the here and now ... there's no sign of deep cold over Europe; look at the above average anomalies on http://www.wxmaps.org/pix/temp4.html, and this is backed up by the GFS 0z. All the deep blues are over Canada. So any cold weather will have to come in from the Atlantic, and indeed the charts show weather systems approaching from that direction. Trouble is, any cold air gets modified to the point where any snowfall piles up over the Scottish mountains, not lower down or further south. Good for the ski industry, but only brief snow flurries down here if that.

Arpege predicted snow depths for Sunday evening - a little further south than the Midlands but we’re talking a few tens of miles and it will keep being adjusted.

I thought those maps were derived from the GFS model?

Our cold weather has never come direct from North America; if the northern arm of the jet fired up we’ll have mobility and average to mild weather.

Friday looks interesting for many as the showers pack in from the NW

https://www.theweatheroutlook.com/charts/gfs/00_24_preciptype.png?cb=922

IMBY should get a cover as many in line with the Cheshire gap

https://www.theweatheroutlook.com/charts/gfs/00_30_preciptype.png?cb=922

Snow showers still feeding through at 15:00

https://www.theweatheroutlook.com/charts/gfs/00_39_preciptype.png?cb=922

Finally start to fade at 21:00

https://www.theweatheroutlook.com/charts/gfs/00_45_preciptype.png?cb=922

It's also been a very good start to winter for the European ski industry, and getting better. The forecast for the Portes du Soleil, for instance, has snow every day for the next nine days, and a metre of new snow due by Monday. Very different from the drought and mild temperatures of the last two years at this stage. 

Sunday's fun looks at tad further North this morning

03:00 frontal system moves in snow on the leading edge heavy in parts of NI

https://www.theweatheroutlook.com/charts/gfs/00_75_preciptype.png?cb=922

0600 sees Snow across parts of Wales / Midlands and down into the SE

https://www.theweatheroutlook.com/charts/gfs/00_78_preciptype.png?cb=922

Moderate snow into the Midlands N Wales and parts of the North......turning to rain further South 09:00

https://www.theweatheroutlook.com/charts/gfs/00_81_preciptype.png?cb=922

15:00 as the front moves away snow edges further South

https://www.theweatheroutlook.com/charts/gfs/00_87_preciptype.png?cb=922

Monday also has potential

https://www.theweatheroutlook.com/charts/gfs/00_99_preciptype.png?cb=922

Midlands and parts of the South see snow

https://www.theweatheroutlook.com/charts/gfs/00_102_preciptype.png?cb=922

GFS 0z has rain for most on Sunday with snow confined to northern England  

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&CONT=ukuk&MODELL=gfs&MODELLTYP=1&VAR=prty&WMO=&ZOOM=0&RES=0&PERIOD=&PANEL=0&ARCHIV=0&BASE=201712070000%26HH%3D84

Here's the Arpege 00z view for 09:00 GMT Sunday. One thing I have noticed is it shows significantly fewer showers pushing inland tomorrow than GFS which isn't all down to its higher resolution. Also it is much less keen to turn precipitation to snow over the ocean areas than GFS. I've cross referenced the TWO plots with other sources and they are correct representation of the data. 

Broadly similar to the snow depth chart from Arpege that I posted earlier - on this run the snow extends a little north and east through Sunday.

My sense is that the overnights have pushed Sunday's slider system just a whiff of a hint south. More runs needed but another 100 miles or so the populous areas of the south could hit the jackpot. Slowly, slowly catchy monkey would be the optimist's take. 

That seems strange in that the heavy areas within the white snow area are shown with the green heavy rain shading. Is it a rendering problem or does it indicate snow/rain mix?

Yes, there’s still a lot of uncertainty on the track. We have to remember that the LP hasn’t even formed yet: another 24 hours.

It’s still possible it could slide even further south or push north: how the LP develops, how it responds when it starts to engage the Arctic airmass as it approaches the country.

disappointing runs this morning. and longer term outlook seems poor as well as mentioned with the pv moving back to greenland

still time for another shift but not looking good

That's snow. It's purely down to the opacity level of the white shading that is used.

Looks impressive to me? this one into 15th? 1040mb Greenland and 1040mb for OVER THE N. Pole. - Giving us a northerly albeit a slack one.

Re the comments above about the longer term outlook not looking so good as it had done. That certainly looks the case going by this morning's op runs, but if there is anything the many chops and changes in the models we have witnessed lately should tell us, it is that FI starts pretty early right now, I would say less than a week ahead.

As for the few days leading up towards Xmas, I not really giving that any thought at the moment as that is deep FI territory on the GFS runs at this moment in time.

In the great book HH Lamb "The English Climate there is a table of singularities.If I remember right there was a tendency for a breakdown to Atlantic activity just before Xmas.

In terms of the longer term changes  now it is worth looking at the GEFS out at 240h and 360h. At 240h the ENs are roughly 70:30 cold:mild and at 384h still a cold majority. 60:40.Against this in terms of snow activity on the op run after the Sunday/Monday slider the other Atlantic troughs look a bit further north with snow likely to be further north as well.

I think METO have done a pretty good job so far in a difficult forecasting situation.Until there is a significant change in the METO December forecast I'll be keeping the faith.

If anyone is confused or would like to know the location of the M4 please see below:

http://www.wetterzentrale.de/maps/GFSOPEU06_78_47.png

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=72&mode=0

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=84&mode=0

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=96&mode=0