Yay!!

120 hours is as far as I like to go in this set up.

Suffice to say its an upgrade in terms of snow potential due ot the tilt of the trough pulling in colder continental boundary layer air.

GFS and UKMO totally at odds, Lets hope GFS is right

boo hiss

http://www.meteociel.fr/ukmo/runs/2015011512/UW144-21.GIF?15-17

Explains the lack of excitement from fergie, too mild for the south

The classic 3 way fight between GFS / ECM / UKMO - which side will ECM come down on this evening?    As everyone keeps saying - it's all about the trends and the GFS has shown us a setup that despite the marginal nature of the overall setup, is still able to deliver snow to even the balmy south.  Long may it upgrade! 

There's been an increasing number of off topic posts in here recently....please don't clog up the thread with unnecessary background noise.

Edit: not the last few posts I hasten to add.

Chance of a bit of snow across the Midlands and even down into central southern areas tomorrow night on the 12Z

http://www.theweatheroutlook.com/charts/gfs/12_30_preciptype.png?cb=103
http://www.theweatheroutlook.com/charts/gfs/12_33_preciptype.png?cb=103

MetO 144 would be a very snowy chart indeed for (at least) the Midlands north. That's the snag with getting heavy snow in this country, more often than not you're playing with fire and invariably some areas will miss it some of the time. You need an active low in order to get really heavy frontal snow but there's likely to be a warm sector somewhere nearby!

The borderline would be close to southern England on that chart, in fact, although as it's a snapshot of a fast-moving system I daresay it wouldn't be long before the cold air moved back in to cover all areas.

The 120 chart is also cold enough for snow for most of the UK.

GFS is a quick sinker this time.  UKMO would be better for a longer cold spell

Helen mentioned it as well on the Beeb forecast

Regardless of what exactly happens next week, it does now seem to be a fairly clear indication from the models that the recent spell of zonality may be coming to an end at least for a while. IIRC some model runs this time last week, especially those from the GFS, were indicating the zonal spell lasting until possibly the last week of January. There really has been quite a turnaround in the operational runs since last weekend.

GFS something of a Murr sausage. Still good for the South. I'd rather have a proper High latitude block to be honest

http://modeles.meteociel.fr/modeles/gfs/runs/2015011512/gfs-1-192.png?12

Thickness values look pretty low on that chart.

PS: Fergie's comments were made this morning I think before the 12z was even initiated. 

EDIT Around 520 to 526 in the south if I've got the colour scale correct.

It's worth mentioning again how well the ensembles have handled the end of the mild zonal dross. Two weeks ago they first picked up on a decent chance of it and although sometimes it was as low as 35% of the runs it was generally around 50% of the runs which showed a transition to cold weather. In the last week the colder cluster gained more and more members and, well, you know the rest!

It's a good reminder that using clusters, as the Met Office themselves use, is the best way to use the ensemble output. The operational runs are fun but time and time again you'll find some folks looking at them to the exclusion of the rest of the suite. There's a reason the Met Office have their own ensembles (MOGREPS) and ECM cluster ensemble product (DECIDER) after all!

Talking of the latter, look what I've found! I guess that explains why Fergie mentions Shannon Entropy, as it's a graph within the DECIDER suite! (This is sample data rather than the real thing, which I suspect costs megabucks...)

http://modeles.meteociel.fr/modeles/gfs/runs/2015011512/gfs-0-222.png?12

THe high cant collapse thanks to the troughing further south. Assuming we have snow cover it should remain very cold at the surface in the south,

But its not a good run beyond day 7 with the loss of northern heights

Not that bloody Shannon again!

http://www.wetterzentrale.de/pics/Rtavn22217.gif

Still an ice day thanks to surface cold and hopefully our snow will be intact

I think with his job he has to be impartial. 

I make it 526 for Kent (522+4) to 528 at Land's End (519+11*0.8)

Note that in the SE the wind is coming in from the SSE, so there'd be lower dewpoints pulled in from the mainland - hence a higher risk of snow.

NAVGEM's take for what its worth

http://modeles.meteociel.fr/modeles/navgem/runs/2015011512/navgem-0-150.png?15-17

Ive gota say - sorry to poop on the party. But the charts at this stage have been consistent with a dry message than a snowy one. A fact that reflected in the BBC 5 day forecast.(amongts others)

At this stage, I would say if any snow does arrive, it will either be transient (Due to no deep deep cold), very local or be just a couple of CMs here or there.

Im not seeing any huge precip being forecasted at this stage, which is a shame.

EDIT:

This makes my point quick well:  (total accumulated precip out til next friday) 

I think alot of people save for parts of Lancashire will see this cold spell through being cold and dull.

This chart illustrates perfectly the importance of drawing in a cold continental feed for many of us in the southern half of the country when there are frontal boundaries knocking around.