I think your last sentence is key Darren unless people want to fall into the old rollercoaster of emotions.

Yesterday evening was good, this morning a little less so. This afternoon will be? Who knows!

The overall changes are small on a global pattern scale but the UK implications given our location may be significant. Still, with the amount of uncertainty I would hate to make a forecast for next week!

I think were all in agreement that its too early to say bye bye to the chance of cold air just yet, but the time appears to be getting closer on the evidence presented thus far.  It is the rainfall situation and storminess that will probably come to dominate the first third of January. I find that tracking a possible cold snap is pretty much  pain free as long as you accept that its very much an outside bet, which this coming possibility always has been. 

Yes, uncertainty really is the key point this morning!

ECM means still good for the 5th and 6th which suggest the ensembles will be similar to the 12z yesterday. It's blown away after that though so a small window for snow. 

http://www.wetterzentrale.de/pics/Reem1682.html

http://www.wetterzentrale.de/pics/Reem1922.html

Hmmm, I wouldn't say blown away by the 6th as the -5c 850 covers more of the UK on the 6th than the 5th and with a continental flow would be cold enough for snow.

Good ENS in my opinion.

Will be interesting today to see if the MetO acknowledge the risk of colder weather although I think they have done the right thing so far in playing it down.

Andy 

0z GFS shows a constant succession of storms and associated wind and rain over the next 10 days. Each low in a slightly different position but will likely be very unsettled for all. After Frank there is the potential for further low pressure systems to affect parts of the UK on 1, 3, 4 and 7 Jan. Most of these unlikely to be named but could still have some impacts particularly in areas with already saturated ground.

A lot of uncertainty in the output at present but GFS has been hinting at significant low pressure systems on 1 and 4 Jan for several days now.

1 Jan - this one is filling as it reaches the UK so only western areas likely to see much in the way of impact

http://modeles2.meteociel.fr/modeles_gfs/runs/2015122900/90-515UK.GIF?29-0

3 Jan - north-western areas at risk from this one

http://modeles2.meteociel.fr/modeles_gfs/runs/2015122900/132-515UK.GIF?29-0

4 Jan - a nasty little secondary low zips along the Channel

http://modeles2.meteociel.fr/modeles_gfs/runs/2015122900/156-515UK.GIF?29-0

7 Jan - a major sub 950mb low approaches the west of Ireland

http://modeles2.meteociel.fr/modeles_gfs/runs/2015122900/228-515UK.GIF?29-0

The slider low scenario is always a very tricky one for the models. This mornings output is so close to an easterly in the 120-168h slot but models seem to be veering towards snatching defeat from the jaws of victory. METO looks  the most promising at 144h although the LP movement from 120h looks a bit strange.

ECM ens for SW Holland - control has flipped to mildest of all 50 solutions around the middle of 4th! Op and Control both in mildest 10 on 5th.  This on the run with the greatest amount of cold options. 

Not much has changed this morning maybe the block to our east is pushed temporarily back to Western Russia at the end of the run, other than that the NH profile is looking good with the PV being pummelled from all directions and the chance of snow for some as early as this weekend, and this then continues into next week more so for Scotland and the NE.

I agree. The block is a reality. Surely anything is possible from here whether good or bad for us cold 'fans'

Question for anyone in the know. If a computer model is a system does it have to settle after a step change in input as would a control system. Change the input on such a system there is a settling period with overshoot and undershoot of the output. Could this analogy be applied to the model output?

I would have thought this would be the case (to some extent and probably effects more the mid to later areas of a run)

StuH

Thurlstone South Yorkshire Pennines at 230m AMSL

Hoping that the cold wins out sooner or later.

It certainly looks as though now that temps across the country are going to take something of a tumble compared to the last 7-8 weeks, even if we don't get the much sought-after cold easterly. With the Euro High gone, depressions will be able to travel further south than recent ones. The mild weather has not been as persistent up here as down south this month & last so any cold weather won't be so much of a shock to us, but I imagine for those in the south that next week will feel almost baltic compared to recently!

On balance I don't think there's much change this morning. The output is a slight upgrade for mild weather fans but nothing more. On the flipside of the coin yesterday's runs didn't suggest a cold easterly outbreak as the most likely scenario either. 

I have to wonder with all these depressions bumping up against a block, how little it would really take to cause several historic snow events. We are clearly close to something really special, the 850hpa gradient is unusually high; more like newfoundland than the UK.

That's obviously the case. However, older hands than you will know that 95 times out out of 100 something conspires to prevent this happening in lowland Britain. Of course this time could be one of those rare exceptions but the probabilities suggest otherwise.

Spot on David, thats my first aim, getsome colder weather here, even temps of 5-7 will feel quite cold and a shock IMO

The 6z is frankly disturbing with frequent bouts of heavy rain and gales or severe gales at times in a very cyclonic synoptic setup. The deep cold air is maintained just across the North Sea in Scandinavia and edges gradually closer with each departing storm. By 240 hours Scotland and the NE become really quite wintry.

EDIT...A height rise over Greenland could be the golden ticket we need to get the cold to properly advect southwestwards. At 240 hours there is evidence of this.