kold weather

It does, however dare I say this... Its a little Dec 62 in the way it looks around 168hrs....

Yeah thats a heck of a run for the north thats for sure. Eventually as the low develops and moves SE the south also joins in the party. Anyway this run on the 18z GFS certainly been to the pub... However as has been said, still time for that to go wrong, especially with where we are at 120hrs, I'd not feel comfortable till thats inside 72hrs to be honest.

Quite a large snow event for northern England on the 18z run, again perhapd on the marginal side for settling snow, especially nearer the coast, but the hills get battered on this run, and ,my guess is so would lowland areas as well, more than is being modelled anyway. Also - note the upper cold coming down from the north, this is going to be a stunner of a run in deep FI as well.

ARPEGE still one of the further south runs, though still gives something to look for in the south of England, especially below the M4. It actually slightly lifts it northwards/strengthens it over the SE btw which gives some snow to the SE region late in the night.

Good looking set-up again on the 18z GFS, a marginal event again on for much of England, the wind angle isn't the best so maybe a bit of a struggle though the air is fairly cold so it maybe just on the right side, especially further north. We will see! However that is a great looking block, looks nicely positioned for a second shot from the north that is just starting to feed down the E.flank of Greenland.

To be fair also it would only take a really awkward little shortwave to run between Iceland and Greenland (did we used to call it GIN, or something like that!) and the whole of FI will start to look different. I'd say FI is probably quite close in at the moment, maybe 96hrs? Not that I think thats going to happen, but us oldies on here have been bitten a great many times by such a feature!

I think what BFTP is trying to say is that in many a normal situation that set-up would indeed topple, but that with the set-up sloft as it is its going to retrograde to some extent up towards Iceland/Greenland. This run is a little colder aloft due to more of a high pressure influence. A more conservative evolution and probably more believable than the 12z GFS which was rapid! Time for another Cillit Bang run!

Yep also being shown on the 18z GFS as well: It'll probably usher in some more marginal air behind it however based on what I can see. Still definitely a decent shot at snow in the north from this feature, though way too early to tell of track and maybe partly dependent on the LP that swings across the south first. Both suggest 5-10cms possibly for some areas in the north, less as it comes further SW and gets more marginal.

The 18z GFS is pretty close to bang on the mean position of most of the models. Good to see both the GFS and ICON shift a little northwards though to come more inline with what the ECM has been showing today. Will have to see what the other runs do down the line with it tonight. Should they show broadly the same on the 00z run then confidence will increase in a snow event for Wales and southern half of England, though where the northern extent is remains to be seen. The good news is it looks like an evening/overnight event, which will help tip it towards being less marginal and better chance of settling.

Yeah something like 1-3cms mainly, maybe 5cms in hotspots if the 18z ICON is correct. mind you once it starts to snow the models may well underestimate the cooling that would occur within such a set-up from experience which may well help to give a little more snow on the ground. Still definitely further north than the 12z run. We will see what the 18z GFS comes out.

Decent 18z ICON, as others have said its definately further north which does make it a little more marginal for the far south, but a decent band of settling snow either side of the M4. Nothing too extreme on this run, probably 1-3cms widely with maybe more on higher ground.

Looking at the radar the 18z ICON looks about right which helps to be give some confidence to the above. Interestingly the model is more keen to have any settling snow during the day, which rather goes against what I'd expect, however it looks like it allows snow to settle along the path of the strongest precipitation.

Interestingly the 12z global models shifted northwards, whilst the higher resolution models stayed a little further south. This far out and given the feature hasn't even developed yet I'd favour the globals over the higher resolution models, though they should be getting a better grip one way or the other over the next 2-3 suites. UKV is probably on the southern end of the range of options, though its well within the range of options. Personally I'm not getting invested in snow events this year, so if it comes off then obviously huge bonus!

Yeah thats abit of a stonker, the evolution is certainly on the table. The threat of a rapid switch over to a west based -ve NAO has reduced somewhat today, and even if it does happen the mid atlantic block looks to hold long enough that any LP attack from our SW starts from a decent position instead of starting way out in the mid Atlantic like some of the models were trying before.

Worth noting that alot of those runs that do get warmer are doing so because they are developing a mean ESE airflow as a LP rolls through Europe = classic surface cold type set-up with warmer air riding above. Of course, if the wind were to then shift back eastwards we may find we can only tap into a marginal easterly flow for a short while if the cold pool is shoved too far north from that ESE flow.

By the way the ECM 12z control does something very similar to the OP where it swings the front back westwards again. Several models have recently been doing this set-up (ICON has toyed with it several times) so worth keeping an eye on. Very strong agreement of snowfall across the southern half of the UK btw from the ECM ensembles, though some still are a little further north than the OP. Not too many further south.

For you guys back further east thats almost in holy grail territory, if it just stayed even 20-30 miles further west you guys would be in for 12-18hrs of heavy snow, hotspot would be 25-30cms. Of course, realistically the ECM is an extreme solution of course and no doubt as Steve said the Euro4 will be right just to frustrate us! The GEM today comes in at a solid no.2 (!!) when it comes to Wednesday. I'd bank that as well right now. BTW for todays set-up, rain at lower levels but went to the south downs where past 2pm it was predominantly wet snow though didn't settle. Should we get a similar situation on Wednesday I'll probably head back up there again.

Steve I'm probably going to regret this, but if it ends up too far south, we would be basically primed for something that looks similar to Dec 62... Not saying the long term would look like that winter, but that IMO is what happens even if it does sink somewhat. If it does, its not going to be hanging around our shores for long.

Looks like the high resolution models are indeed further south than the global which is obviously interesting to see! If there is going to be an error, I'd have thought it was to the south. Then again thats far from certain of course. I'm quite far south so only the ICON would probably miss locally for me, however I hope those models do adjust northerwards with time. Getting to the timeframe where the real high resolution models will be running it.

I do agree with you on the cuation side of things, we've been around the block and have seen these both succed and fail before! With that all being said, I've got to be honest and say I've rarely seen the stratosphere and troposphere both so primed for northern blocking in the 16 years I've been here. I think if we end up with a high over shores it isn't hanging around for long before it gets scooped back up...indeed some of our very best winter spells have come from such evolutions. If we do get lucky, we may end up bypassing that stage and just go straight into an ever cooling easterly flow, which at first won't be that impressive but hold it long enough and there is bound to be a proper injection of cold air into the systreml

Euro4 is just too far south and perhaps a little weaker as well than the other models. Shift that area up about 100 miles and it wouldn't be all that different from the ECM, maybe just as I said a little weaker and not quite as extensive as a consequence. Its within the range of what is possible, though thankfully right at the southern end of what is likely at this point it seems.

That is a very tasty looking chart at 216hrs: Its sooo close to something really special, might just need a slightly stronger trigger low running down the eastern side of the upper high...

Yeah for some areas around the pivot point its close to 24hrs of constant snow. The thing is whilst it probably is somewhat extreme in just how far it swings the LP back SW, the general idea of the LP stalling out and maybe doing a cyclonic loop is certainly possible. Where that happens of course is where things are uncertain. Also, the models do tentatively seem to be zoning in on the location as well. If I was somewhere along the M4 I'd be feeling increasingly confident of a snow event on Wednesday...but still time for it to slip too far south. That is where the error will be, if there is an error.

Eermmm ECM 12z! Thats an outstanding event from Wednesday-Friday! I'd have banked Wednesday's event anyway (I'd be right on the margins of where the snowline would be, but with the downs nearby, I don't mind too much) but Thursday then takes it upto 11. Yeah, thats a ramp...sorry if its not objective, but that runs deserves a ramp even for that first part, regardless of how it evolves down the line

Yes, I posted a little earlier this eveing that there is a legitimate chance at a very special set-up evolving out of this, especially if we do get any slight relaxation of the upper high somewhere between the 5-10th which could allow an attack from the SW. If it digs in we could get a straddling front stuck over our shores with a wave of cold air coming down - something very similar happened back in Dec 62...should we get another burst of upper highs forming we are going to be stuck then with a very cold set-up that won't even need decent temps aloft, the surface will do the job itself to a greater extent even under less than optimal set-up. Anyway before that as you rightly say, there is some good winter set-up here, it is borderline and I suspect time of day, etc is going to make a world of difference as to where gets settling snow or not.