That's an odd south-westerly

To clarify - I don't mean under our current Universe's physics laws, I mean if water's freezing point was 10 deg C, not 0. I am one of those who thinks snow at 10 deg C in our universe is pretty pants as it vanished like snow in an oven. That said I recall a superb streamer in the 80's that gave a 6 inch fall of very wet snow to my part of South Wilts (small village called Shrewton, near Stonehenge) in April (poss 1986 or 87?). Looked great at dawn, had gone by the time I came home at 5 pm.

Little bit of history about that intresting read

http://en.wikipedia.org/wiki/February_2009_Great_Britain_and_Ireland_snowfall

It would probably be disastrous, the increased albedo would send the earth into perhaps the most severe ice age in hundreds of thousands of years. 

They're still there
I guess if maxes of +6/+7 (IMBY) for a few days constitute a cold spell then things have changed.
I agree the uppers however are interestingly depressed for a maritime source but I would think the parameters that go against snowfall such as WBT and dp will be the wrong side of marginal for areas close to the sea or below say 150m, which might rule out much of lowland Southern England. Bring it on though - I would love to report a snowfall before the end of this week.

dp's look fine Neil:

http://expert-images.weatheronline.co.uk/daten/proficharts/en/euro4/2015/01/12/basis06/ukuk/taup/15011400_1206.gif

Hmm, I wonder if GFS(P) is going to bring that LP through the channel:

http://modeles.meteociel.fr/modeles/gfsp/runs/2015011212/gfs-0-96.png?12

I'll try and get some snow maps showing for tonight, they should be better than the 850s as they take into account the whole section of the atmosphere from ground to cloud. That is provided the firewall doesn't block my attempts to download data from NOMADS which it is at the moment.  

GFSP bringing some deeper cold pooling southwards:

Really cold end to the GFSP, the block over scandanavia created because the atlantic is simply to weak to stop it. Note even if we don't get this scandi high, we will probably get something just as good, the atlantic is really giving up completely.

Yeh...

This is never going to pull off, but it is literally one of the snowiest charts I have ever seen <240hr. Certaintly a top 10 if not a top 5.

Not that much snow on it Quantum:

GFS 12z has a sliding low on Monday crossing within cold air, snow for a fair few is a possibility I would have thought!

Yes not deep cold so very marginal - much like boxing day night I suspect.  Still, might look promising early next week if some of the output were to verify.

NMM showing heavy wintry showers packing into Wales and into the Midlands. I think many will see falling snow, accmulations though is a trickier matter.

Well this is all a bit nuts really... GFS and GFSP trending away from the quick removal of the ridge shown on recent ECM runs, the amplification increasing further and further with each  new run, even within the 5-6 day range.

Awaiting the MJO update with interest, as this sort of trend seems like what would be expected if the MJO was continuing to exceed expectations.

If you don't mind, I will now indulge in some excited summaries before bringing down the inevitable hammer of uncertainty:

GFS is further east with the Atlantic low than GFSP for day 6, so we don't see quite such a strong mid-Atlantic ridge up through Iceland bringing cold air down from the north... but the overall pattern is more or less the same.

We then see the more progressive GFS bringing the Atlantic trough into play on day 7, but the eastward momentum is reduced from previous runs, which means that rather than having a well developed trough extension attempting to wedge in under the ridge, we have a weak low that promptly slides SE for day 8, producing a considerable snow event for about 3/4 of the UK.

As for GFSP, the ridge on this run is so resilient that the Atlantic still hasn't broken through by day 8, leaving us looking to disturbances in the cold air mass for snowfall - not as snowy to this point in time, but better going forward as HP over Scandinavia has more time to establish and grow in strength.

The real snow chances come days 9 and 10 as a disrupting Atlantic low lets loose a weak disturbance that slides SE under what is by that time a seriously strong Scandinavian High.

Both GFS and GFSP blast the blocking away as soon as they hit lower-res. The way it happens on GFSP is just shameful, with a marked mid-Atlantic ridge (good for reinforcing the Scandi High) suddenly collapses. Can't believe we still have to put up with that even after upgrades.

Never mind the lower-res, the trends in higher-res GFS and GFSP are what count, and they sure are fantastic if you're seeking a more prolonged cold spell with greater depth to it at times.

BUT... (warned you this was coming!)

The route to the potential slider low/Scandi High combination remains highly unclear when you take into account the UKMO 12z op run, which actually looks like an even faster version of the ECM 00z op run. This route places the Atlantic low much closer to the UK days 6-8, and we rely on low heights extending SE from us to allow a build of heights to our NE, with any continental flow taking longer to establish - probably taking until at least some 10-12 days from now.

Then there's the GEM 12z op run. It's rather out of line with all of the other output, as it merges an Atlantic low with the trough to our NE at a time when all other output slides that low toward Portugal. It maintains the cold trough close to our east, with further Atlantic shortwaves feeding in, right out to day 8. A snowy outcome, but reliant on all other models having that Atlantic low modelled wrong in the 5-6 day range.

So overall, massive uncertainty prevents much faith being placed in the GFS/GFSP trend, nor the persistence of UKMO (and I suppose GEM) with the fast push of Atlantic energy days 5-6.

In many ways UKMO is showing a highly unfortunate outcome - the Atlantic troughs don't phase when needed to support the ridge, yet do manage to phase a day later, when the resultant trough is able to flatten the Atlantic jet instead!

The op runs from most of the models have either had no phasing at all (e.g. GEM 12z op) or a phase in the right place to support the ridge (GFS/GFSP 12z ops). Both have their merits in terms of cold and snow potential.

ECM showed how even this unfortunate outcome could work out alright eventually, but it's not the route I'd like to like if I'm honest - too much time for something to go wrong.

A few ENS runs on the 06Z GFSP developed a sliding low on Sunday. It seems this signal has now been picked-up by the GFSP OP. An interesting scenario if like me you were thinking it was back to square one from Monday.
Note if all goes to plan the GFSP becomes the GFS stat on Wednesday.
So what does it mean if the slider does occur? It means I'm probably £100 out of pocket but I'm sure it will be a good cause and I won't begrudge it at all

No apologies for the MBY theme on the above , hopefully I might ( and others) get to see something soon

This just in from NCEP:

NCEP diagnostic discussion update:

SYSTEM MOVING THROUGH SOUTH CENTRAL CANADA WED & THU

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GFS/NAM/CANADIAN COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE 00Z ECMWF IS A SLOW OUTLIER, EVEN WHEN COMPARED TO ITS
ENSEMBLE MEAN, WITH THIS SYSTEM.  AS THE PARENT SHORTWAVE IS
MOVING MOVING THROUGH BROAD CYCLONIC FLOW, A FASTER SOLUTION MAKES
MORE SENSE ANYWAY.  HOWEVER, THE 00Z UKMET IS ON THE FAST SIDE OF
THE GUIDANCE, WHICH IS ITS USUAL BIAS.  A COMPROMISE THE 12Z
GFS/12Z NAM/00Z CANADIAN IS ADVISED WITH ABOVE AVERAGE CONFIDENCE.

The bits in bold both put GFS forward by comparison. It also suggests that despite similar results in terms of trough behaviour, the lack of favourable phasing happened as a result of the Canadian system being too slow on the ECM run, yet too fast on the UKMO run.

Now this does imply that we are relying on a 'Goldilocks' outcome with not much room for error without the whole thing unraveling. 

The UKMO 12z is the fastest of the models so far this evening so it could be up to the same tricks - though I wasn't aware until reading the above that it actually had a verified bias in this respect.

Having the American pros behind the GFS/GFSP with it's ideal outcome at 5-6 days range is encouraging, but unless ECM comes into line with them on it's 12z run today, I'm going to remain about as cautious as it's possible to be with regard to the potential for Scandi Height rises starting about a week from now.

Likely to be a lot of ens divergence from this point. "A where did that come from Easterly" or back to square one and Neil's money safe 

http://www.meteociel.fr/modeles/ecmwf/runs/2015011212/ECM1-144.GIF?12-0

Remember it well and still have the photos. It dumped around 3 to 4 inches of snow in no time whatsoever, literally a couple of hours. An actual Severn Streamer, and the only one I can recall since I've been interested in the weather.