Yes, some consistency from ECM about a cold snap - at least - from next Tuesday.

The UK map shows the potential for wintry precipitation well - although obviously the detail will change run to run - but for now this says 'snow' to me, with 500-1,000 hPa values in the mid-520s for the Home Counties and a marked trough and small LP.

It seems that for a change, all the models (GFS, ECM, NAVGEM and GEM) are in some kind of agreement with a change to colder conditions at around the 12th. That is a signal too strong to disregard.

However, 7 days is still a long way in forecasting terms so there'll be some chopping and changing as we get nearer to the time. All we need now is for it to come into UKMO's range.

It still doesn't look likely this will be anything but a short albeit very cold blast from the North, the lobe of PV coming out of the Canadian sector will halt any height rises pushing towards Greenland.

GEFS P12 and 19 looking great this evening

A number of others bring -10 850s very close to the SE

I've been lurking on this thread for a few weeks now, I remember a few folks predicting a cold spell in Mid-January, at last it is looking (almost) likely

Good to see the chances of a cold spell, however short-lived it turns out to be, increasing with each run  As Ian says, it'll be even better to see UKMO on board nearer the event 

SC - are you able to illustrate your thoughts with any links please? 

Edit: to be honest, I can't see any cold being longer lived than a couple of days with the ECM evolution. 

By day 10 though the GH is reflating again and the PV over Canada is being pushed back. Looks like a sustained cold spell is on the cards at day 10 to me.

 http://www.wetterzentrale.de/pics/Recm2401.html

You may be right but I wouldn't assume that the LP over eastern Canada (eastern Quebec) at day 10 is necessarily coming east.  There is a reasonable chance that it might head north - look at the WAA being pulled north ahead of it.

I wonder what a Day 11 chart would show?  I would guess that the slack LP over Iceland will run SE and that LP over Quebec will head up the western side of Greenland.  The dream scenario for cold weather fans would be a link up to the Arctic High - something that the GFS 06z this morning was showing.

I am an optimist most of the time I admit but there is room for optimism especially when you have ECM Mean charts like this.

http://www.wetterzentrale.de/pics/Reem2161.html

Pretty much what I thought too

Whether we get a toppler, snap, spell etc. is very much dependent on that WAA, how it's aligned and whether it encourages that HP further North and towards that lurking Arctic High. The Atlantic doesn't look like it's in full rampage mode to me which at least suggests any toppler would be a bit longer than the one day wonder type, may even get one of those repeating ridging scenarios with milder interludes.

It has been an interesting little flip on the GFS ens from milder to cold - be nice if it stays cold rather than flipping back

GEM is rather nice ;-) 

Not overly cold, but the synoptic setup in its latter stages really is something special. 

Aha! That looks a bit more like what I'd expect to see in light of the signals at play for mid-late Jan. The control run is entertaining in some respects; first it has a shallow sliding low turning a standard toppler into a snowy outcome for some places (below-left), then it manages to turn the toppling ridge into the seed for a Scandi High that brings slack conditions with cold air stagnating across the UK. Not that snowy I realise, but it would be brass-monkeys cold with -6 to -10*C widely by night. 

I've posted that to highlight the alternative cold scenario that the GEFS seems to be playing with this evening. Scanning through the postage stamps, the second WAA attempt is further east than the ECM 12z op run has it on all but two GEFS members.

Despite their clustering on that path, it's not what I consider the most likely route, with a ridge to our NW fitting better with the teleconnection signal, but plausible enough should the second WAA attempt turn out to be in the middle of the Atlantic rather than heading for the west side of Greenland. I'm not used to being this bold in the face of some model guidance but at least it's GEFS I'm in disagreement with and not the ECM ensembles!

How I have missed marveling at cold charts and wondering if they'll come close to reality. It's also been too long a wait to try out the latest chart viewer tools with respect to a potential cold spell of note 

A sensible and realistic post.

There's clearly changes a-foot in the mid-range that have their origins in the next few days. The key is how and where any Atlantic ridging occurs once the annoying Atlantic low shuffles eastward. Many, many, many options are being shown, and quite a few give a cold shot from the north. Some follow with cold from the east.

For me the key is the support from the Arctic high during that ridging process; - and our constant winter nemesis, the trough disruption south of Greenland.

A lot of NH views in the 168 to 240 period look like a Catherine wheel with LP displaced from the pole into four sectors around upper latitudes.

More Interesting Times Ahead.