Snow being the primary source of real interest during winter, I'm not seeing any real signal for that for most. Not of note anyway. The ens paint a gradual warming into the new year after a brief colder and mainly dry spell. 

Yes there is certainly no sign of a prolonged cold spell on this: http://www.wetterzentrale.de/pics/MT8_London_ens.png

A jump to a much milder picture as we enter 2015.

Well how about that then? Agreement on a sliding low that moves fast and has no 'baggage' escaping east to mess with the continental cold  

We've been lucky with adjustments in the 48-72 hour range (yes, that close in time!) because the shortwave from the SW is now looking a bit faster than was the case 24 hours ago, so much so that Boxing Day has turned from bright and dry to increasingly wet with some snow in Scotland, perhaps far-Northern England too.

This quicker movement away from SW of the UK looks to allow a stronger mid-Atlantic ridge to build in behind, helping with advecting cold air to the UK and perhaps fending off the Atlantic later on in time.

So the cold seems to be sorted out now, but will it just be in-situ cold under a strong UK high with the potential for a lot of hard frosts and increasingly dense fog (as warmer uppers invade from the Atlantic), or will it evolve into a longer-lived easterly with deep cold within reach?

The odds are currently in favour of the first outcome within the next week or so, as the Atlantic jet doesn't quite achieve the south to north alignment needed to create the sort of higher latitude block required - let alone achieve an undercut.

Having said that, the low heights in the western North Atlantic are a right mess on the output for days 5-6 which makes for a less than convincing story - lots of scope for shortwave lows to crop up and either help align the jet more favourably or cause it to power NE with unfortunate results (illustrated by the GFSP 00z). There's also the possibility that the ridge will continue to trend stronger in the shorter range which might bring about more disruption of the Atlantic jet.

No point in looking any further into that at the moment, as the exact behaviour of the sliding low still has some spread in solutions to resolve. Some GEFS members and the GFS 00z op still slide it as far east as Germany (but 06z op a little further west), which rather limits the snow potential as stable conditions arrive more quickly from the NW. At the other end of the scale, ECM and GEM have part (ECM) or all (GEM) of the system dropping down the spine of the UK which would be great for getting the cold undercut of air from the continent in while the atmosphere is still unstable enough to produce convective snowfall over the southern end of the North Sea which would then be drawn well inland by rather strong winds.

UKMO represents the current middle-ground, which tends to be the best bet at times like this.

GFSP's 00z had a similar positioning of the low to UKMO for midnight Sunday (+96 hours), but it was a considerably deeper feature and that brings extreme output of the morning, worth a look a think, for entertainment purposes (it's not as intense on the 06z you see):

Can you imagine gusts to nearly 70 mph with convective snowfall (that rain in the east transitions to snow by 6am)...? The flow is from the NE in case you're wondering.

This was by far the most extreme scenario on offer and has been dropped by the 06z GFSP op run in favour of a less intense feature.

In fact that run has the snow off the North Sea getting no further SW than London. Still gusts to 45 mph but with the low sliding down just east of the UK the wind is coming from almost due north so not a lot of use if it's a snow streamer you're after.

On the flip side, UKMO's has a shape to the low that is even better for a snow streamer than the GFSP 00z was, though of course the winds aren't nearly as strong - probably 40 mph gusts.

It's a similar story from ECM too but with a secondary center to the low just east of the Isle of Wight at +96 hours adding a bit of extra interest.

So here we go then... time to start fretting over the specifics 

- but seriously, this looks like one of those situations where even once the track of the low is sorted, the exact shape will also be a critical element. The more the mid-Atlantic ridge is able to extend over the op of the low by Sunday morning, the better - you get a flatter northern flank to the low which improves the easterly draw.

The models will always want to break down a block in low res though.

Oh, time for this one again!

Suffice to say that chart is very deceptive if you take it at face value. So, why not look at its companion chart instead?

http://www.wetterzentrale.de/pics/MT2_London_ens.png

Yes, it's prolonged* cold! Just not "deep" cold, but enough to ensure a nice seasonal feel to things for a while yet.

• My definition of "prolonged" is a week or more.

PS, nice to see -12C at 850 clipping the SE on the parallel run... just goes to show what can happen if the nascent high aligns itself "just so".

Parky! -12c into the SE

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=162&mode=1&runpara=1

06z op close but no cigar. Friday looks very wet all of a sudden

Parrallel is better

http://modeles.meteociel.fr/modeles/gfsp/runs/2014122406/gfs-0-210.png?6

Fair comment Darren. Indeed the 850s are deceptive when you look at the set-up.

Interestingly there is colder air coming in from the west against the block to the east, squeezing out a very thin "mild sector" here

http://www.theweatheroutlook.com/charts/gfs/06_264_mslp850.png?cb=748

I'm really glad you're here to emphasise the nature of surface cold, in fact we should not be surprised to see an easterly coming within something like 10 days of you're emergence from a long hibernation 

By the way... bank:

Thanks in large part to a stronger low development in the eastern Med. and a stronger Scandi ridge evolving days 4-5 than on previous runs. GFS has also shown a similar trend but doesn't push the cold as far west.

Also, the above is right under a large cell of high pressure for the UK, so not a snowy chart away from perhaps the far SE, but the overnight minima would be very low indeed - what a way that would be to see out the warmest CET year on record! 

Edit: thinking about that stronger LP development in the eastern Med. it's definitely something to watch out for as there will be very high levels of instability (large scale ascent of air, cold uppers, warm sea) there which the models may struggle to resolve.

Those who've seen the Dutch ECM ensembles this morning might be wondering what sort of run gives a long spell of subzero highs.

The answer is a large high over or to the north with light easterly winds. As a result, a massive inversion builds and by T+360 thicknesses are over 540dam and 850s are between +3C and +5C, yet surface temperatures are well below zero.

Incidentally, the same applies to the UK at this stage - away from the SW, temperatures are also below zero, despite 850s above zero and thicknesses in the low 540s.

Can I just second this sentiment. I have read through these discussions regularly for a few years or more now (I never post as I have no knowledge), but with contributors of the like of Gibby, Stormchaser and Gavin P - even all of Q's charts colours and 'fandangles'  etc I even feel as if I am learning something

How these folks find the time to contribute in the way they do is simply beyond me, but it is hugely appreciated as with out those contributions the likes of me would be totally at a loss as to where to start.

Cracking work forumeers!

All the best

If that were to come off it'd be an excellent example of contrasting airmasses: even the -5C 850 stuff to the west would be milder than the air it'd be displacing from the UK.

It's interesting to see GEFS and EPS this morning both showing a sizeable inversion likely to form, even if we don't get much of an easterly flow.

(And I appreciate that if you're in northern and westernmost parts of the UK it's unlikely to be that exciting, but the prospects are more interesting than they've been for a long while further south and east! Frankly I'd take even a zero chance of snow just to get a run of decent frosts - something that's been absent for a couple of years).

I love the -39c over Lichtenstein and parts of western Austria, but -27c for Dortmund, Bonn, Cologne and Dusseldorf!?

A touch in inaccurate!? If not I guess people in central Europe will have to wrap up and warm to celebrate the new year.

Nice trough disruption on the GFSP! http://www.wetterzentrale.de/pics/Rpgfs2341.gif

Not far off being very tasty indeed http://www.wetterzentrale.de/pics/Rpgfs2641.gif

Absolutely no need for despondency in my view. We have potential in high rise across the board, the Parallel sets up a very optimistic NH profile, whilst the op goes mad (not for the first time in the last 24 hours) with strat warming over Greenland - splitting the vortex just as the 12z did yesterday. Plenty to go on from there!