Next weekends cold NW'ly continues to model interest for Scotland and many parts of the north with higher elevation. Distribution of the wintry showers will be more focussed towards the east coast given a more direct northerly.

UKMO is not a snowfest.

My calculations are roughly 522dam in Scotland (good enough) to 529dam air in the SE (rain, if showers or troughs make it this far).

I reckon with the air mass being sourced from higher latitudes this time around when compared to last week, there will be at least slightly better parameters for producing snow as opposed to rain.

For example, the GFS 12z has dew points below zero almost nationwide throughout Thursday, even across much of the North Sea. Could change of course - indeed usually I'd worry about the model not picking up on some mixing out of the cold at lower levels, but this particular run is actually relatively tame compared to the UKMO 12z which has both a deeper low and a better alignment of the flow, for both Thursday and Friday. Not much precipitation away from the windward coasts though.

Precipitation is, as always, a big head-scratcher, and that won't be resolved until the short range. Obviously windward coastal regions look well placed for a lot of snow (or at least wintry) showers.

We then see that mixing out of the air does turn things more marginal for the weekend on the GFS run. Looks like a bit less of an issue on the UKMO run, but mainly because it has such a clean low with a lack of shortwaves that has to be viewed with some skepticism. I think shortwaves are probable, and that the results next weekend are likely to be hit and miss with a lucky few doing well.

There's then the potential for another push of cold from the north early next week, and the big question becomes how soon that will be cut-off by the Atlantic, if it happens at all. It comes down to how much of a vortex is over Canada, to what extent that interacts with LP in the far-western North Atlantic, and how the vortex is split by high pressure across The Pole.

There is a strong tendency in the ensembles, appearing in various op runs too, for the split to break down by day 9 or 10, with the Canadian vortex drawing the life out of the Siberian one and becoming dominant over the following few days.

The most concerning development this evening is the loss of the strong ridge to the pole from Alaska by just +144 hours on the GFS and GEM 12z op runs, which is a significant departure (and downgrade) from the 00z runs.

Thankfully UKMO has not followed suit, with the ridge much stronger even at +120 hours (and notably stronger at just +96 hours), so the panic button can remain behind the glass panel, at least for now and hopefully for a long time!

No complaints about the ECM, still a decent run, a tad different to UKMO at this stage

James - Thank you for your interesting/detailed posts.

You highlight well the difficulty in keeping all the balls in air at the same time when it comes to our winter weather!

Nice from ECM

Day 9 and ECM still holds its form, well into FI

If less than two years is "many a year"! March 2013 had -14c across the middle of the UK. 

ECM ends up with a block still our West

Lovely snowy run from ecm probably the best of the winter. 

January looks as if it's going to end on a rather cold note, unless the models have next week completely wrong!

Quite a contrast to many of the operational runs we were seeing just after the turn of the year which suggested that January may have been a write-off for cold. Sometimes, one never knows. I think that in some ways we've been pleasantly surprised this month at what can crop up at relatively short notice.

Some great contributions in here this evening. As I stands we are heading for about a week of cold weather with low temperatures and low heights - a good combination if it's snow you're after. There is some justified and understandable caution with regards detail as we've all been there before, but 'downbeat' is a bit harsh. I'd like to suggest 'realistic'?

It will be a fascinating weekly outlook on Countryfile tomorrow - you know I am a staunch advocate of the MetO forecasts, and if they (as the lovely Tomasz indicated earlier) are pencilling 'wintry' and cold onto the outlook from midweek, then it's game on and chocks away

Phew!! I thought it was just me

J F F as these are loved , ppn turning to snow as it clears the SE

That is an amazing cold front sweeping down on wed afternoon! Could be rain followed by thundersnow as in Jan 2004!

While trying to keep level-headed and expecting nothing snow-wise from this sort of set-up where I live, I still can't stop myself from calculating the thicknesses. On the ECM op they range from approx. 520 decametres on Thursday through to Sunday, before expanding to 528 dam by 240 hrs on Tuesday week.

I'd hope that depth of cold, combined with uppers of -4 to -6C might offer the right conditions for snow at some point even here at a lousy 32 m above sea level.

But experience still suggests cold rain...

Quite correct. The UKMO definitely does not show widespread snow for most of lowland areas. Upland and Scotland a different matter. 

Some of the wise heads in here more seem upbeat about the modelled cold spell that the couple we've experienced so far, which is encouraging (if that's what you want of course), but I agree, nothing is 'nailed on' (why is it whenever that phrase it used, it seems to jinx matters and things fall apart!)

......and I remember those progged northerlies too.  IIRC, in January 2008 GFS was modelling an astonishingly cold northerly with sub-15c air over a good chunk of Scotland and sub-510 dam air across much of the UK 6 or so days out , with comfortable ice days even for the south...... we ended up with a chilly spell with some a few sharpish frosts, but nothing remotely as cold as the LP was pushed east over Europe.  (ECM/UKMO never bought into the GFS view btw).   Based on these experiences, instinctively I'd tend to trust ECM/UKMO over GFS with regard to northerlies, but have no idea whether there's any solid basis for that.

Surely at least one of these 'snow for the south' charts has verify this winter!....

Good post. Of course we could cite verification stats but IMO there is no statistically significant difference between the three main models at 5 days.

And a few have been talking about thundersnow. The 2004 event was an exceptional set-up with a very sharp temperature gradient undercutting an active cold front. The air behind the front was very cold: circa -10 uppers and freezing at the surface.
The CF on Wednesday doesn't look the same beast, and anyone predicting snow and storms is hoping not forecasting.

this winter is the first i have had a view of the extended ecm ens with wintry potential. (last year being a wintry write off)

thus far, the post xmas cold week, the one just ended and the one upcoming have all been signalled by the 10/15 day anomolys. far better than the ncep ens tools which have only shown via the odd ens member and deep fi op run on occasion.

of course, the longevity and depth of any cold have not been that well dealt with  (the xmas one was ok but the one just ended didnt get the azores ridge pushing in and maintained the euro troughing too long)

anyway, the point is that if we had free access to the ecm modelling in the same way we do the american and canadian, then i feel that that we would trust the model far more than we do. 

Wasn't it in 2003 or am I getting my wires crossed?! Was there a separate event in 2003 by any chance? I remember it happened up here too (though not to the extent it did down south as it was just developing as it crossed here), and after looking at re-analysis assumed the temp contrast wasn't as great as I'd previously thought (2003). I could have sworn it was in 2003 but perhaps makes sense looking at the 2004 charts I suppose. 

Also I see there's an increasing westerly element in tonight's GFS for Wednesday onwards. Hoping this trend is nipped in the bud by other models!