I know what you mean - if that moved just a bit further south :-)

As far as I can make out, the Tuesday snow that the 12z runs offer across the S/SW is a result of the main trough centering just a little bit further east, drawing just a little more cold air into the mix, when compared to the 00z and 06z runs.

Just goes to show how little it can take - but that does mean we're only a small adjustment away from having sleet or rain instead.
Classic knife-edge stuff!

Looking further ahead, ECM is not at all interested in reducing the rate of progression upstream.

There seems to be a case of how many eggs to put in each of two baskets;

Option one has a more amplified situation for days 6-8, which allows a tall mid-Atlantic ridge and enhances the first 'wave' of colder air both in terms of peak intensity and the duration. By way of payment, the eventual toppling of the high then requires LP to track toward Iceland before any opportunity to sink south. We are now seeing some hints that this sink south could be undone by the pattern becoming too flat, though I view that with high levels of skepticism given that it only really features on the GFS and GFSP models.

Option two is less amplified days 6-8 with the jet cutting straight across the Atlantic. It brings the initial wave of cold to an end faster, but on the other hand, the jet can track lot further south days 9-10, with the Azores High kept well out to our west.

It's far from risk-free, but at the moment I'm seeing evidence to suggest that this is actually the safer way forward for maintaining a cold pattern that could potentially reinforce in the 12-16 day range. This is along the lines of what Quantum said earlier regarding amplification - I can really see his point loud and clear after that ECM 12z op run .

Arguably, a 6-8 day pattern so amplified as to set up a blocking high to our NE with Atlantic LP disrupting and sliding underneath is still the absolute holy grail scenario, but there's little left to support such an idea so it's probably best to let it go (would enjoy being wrong on this last part!).

But then the Latitude difference between Portsmouth and lets say Bordeaux in the south of France is approx the same as the difference between Portsmouth and Blyth.... 

evening all. If that LP slipped further south and ran through the channel with Northern France taking the brunt of the winds then some areas of England and Wales would see snow. These tracks of LP are hard to nail, but if anything I see it adjusting slightly north with perhaps Northern England seeing a battering, and the snow confined to Scotland. 

Very interesting scenario for sure- probably won't be nailed until 12- 24 hours out. 

Tidied for you Jas

Here is an experimental representation of how cold various runs of the GEFS have been for London these past few weeks in terms of 850hPa temperature. There's a big gap where I lost interest after the December cold potential imploded... I'm only human after all!

The numbers for each part of the bar are weighted in the way shown in the legend (e.g. the total number of times a run crosses the -5*C 850hPa temperature line is divided by 20).

Evident is a peak in 'coldness' on yesterday's 12z suite (third from top - the axis label interval can't be edited on Google spreadsheets, which is a bit of a shortfall) which was largely caused by the 850's looking to hit -7.5*C on the 11th.
That has since been adjusted upward to -6*C... a lesson in last minute adjustments that does highlight the potential for further changes to leave things on the wrong side of marginal for the S/SW this coming Tuesday.
On the other hand, the 850's for the 11th trended colder up until yesterday - what now looks to be the final result is in line with what GEFS were showing when it was at several days range, just as Tuesday's event now it.

What a complicated world we live in 

The low progged for later this week remains a potentially nasty event at the moment.

What IS interesting is the small secondary feature running across the south on Friday. 850's are sub-zero around this so that could be a cause for something white if it comes off and it is the precursor to a strong northerly albeit transitory

18z shows an interesting little feature zipping through Tuesday pm. It is these little features in this type of airmass that could bring surprise snowfalls.

From the perspective of a lowlander, and as an Englishman, and if I may claim to represent in this post the many millions living in urban centres such as London, the models offer perhaps some wet snow in heavier bursts this week and the prospects of some sleet, perhaps even, amounting to some car roof slush.

From a proper winter-snow perspective the output remains poor for most.  If I lived at altitude on Dartmoor or The Pennines or The Cambrians for example, perhaps a farmstead high upon the Cotswold plateau, I might be thinking there would be few centimetres of wet snow but hardly a significant event.  Scotland at height will do well, if you can stand the gales.

Polar maritime air almost always fails to deliver significant snow away from the N and W of Britain, and then usually with altitude.

The main focus of my model watching remains the recent exceptional mildness and looking ahead the prospect of some very very windy weather over the next two weeks with all the hassle that that involves in terms of disruption with ivy clad trees falling over when it is least helpful.  I am expecting the models to start to crank up the storminess big time. I am and will continue to be fascinated by the British weather and there is much interest in the jet driven storms.

Batten down the hatches folks!

WI

Indeed Kev that run looks good enough heavy at times with that feature

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gfs&MODELLTYP=1&BASE=-&VAR=rart&HH=78&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gfs&MODELLTYP=1&BASE=-&VAR=taup&HH=78&ARCHIV=0&ZOOM=0&PERIOD=&WMO=

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gfs&MODELLTYP=1&BASE=-&VAR=hgt0&HH=78&ARCHIV=0&ZOOM=0&PERIOD=&WMO=

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=78&mode=3&carte=1

Some of those  on ecm are interesting to say the least

Perhaps you should have put a tenner on it Brian for your thoughts for Feb could be a very good call!

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=360&mode=0&carte=1

I'm in the West at fairly high altitude and polar maritime air is 99% of the time useless for snow here too. I never get remotely excited about it anymore. It's almost always sleet/wet snow that gives some temporary slush at best and the only proper whiteness is on the tops of the Brecon Beacons/Black Mountains. I can't remember an exception to the rule in fact. Very predictable. We need a proper arctic northerly/NNwly like in November 2005 or December 2010 to get proper snow. People see -6 to -7 uppers and snow symbols on the GFS charts and they get carried away!

The outlook further ahead out to days 10-15 shows essentailly a continuation of the pattern of the month so far with a +NAO but cooler more NWly zonality. Generally unsettled, wintriness mainly for the N. ECM height anomalies day 10, NAEFS day 12

Not always wi when the 528 is ahead of a occluded front  regardless of source a good chance of proper snow on the back edge little doubt not a mild outlook imo either

quote=Whether Idle;660492]

Polar maritime air almost always fails to deliver significant snow away from the N and W of Britain, and then usually with altitude.

WI