ukpaul

It’s much less marginal up here with regard to 850s and ground temps, yes. Through experience the worst place to be is where the charts show snow a few days out, it always moves. North, South, anywhere but staying put! A couple of sliders recently here had one shift to the North and one to tne South. It’s the expectation denied that kills you.

A fascinating run, with a resolute cold pool over us. The way that the Canadian lobe of the PV is allowed to throw low after low without trough disruption looks unlikely, though. Surely it won't leave it until the last couple of frames the way that the 18z does?

GFS will not create a trigger low if it can help it at that point in the run. It flattens everything between 192 and about 240 when it can. EDIT: Yep, predictably it did that.

Not true, for my location the GFS mean shows a max of 1 degree above freezing from 20th to the end of the run.

The ECM is about 200 miles to the East compared to the 0z. Still a similar evolution, just a matter of positioning. EDIT - as the 240 shows.

Yesterday's 12z chart?! EDIT: Already spotted as being wrong chart.

The ‘messiness’ of cold zonality until next Friday or so is part and parcel of the evolution needed, I think. It primes this side of the Atlantic with colder uppers, flattens the Azores High and only then is a Greenie ridge going to be needed. After that, my location has a mean 2m temperature that barely gets above freezing for days and that’s as a result of the lead in and very much in line with the longer range models.

GFS diverges completely from the 6z by 174. The low near Newfoundland that it blew up and which aided the ridge to Greenland is suddenly made nothing of at all. A pretty weird change as it was in the same place and at the same intensity at that point on the 6z. It looks like a difficulty in modelling the jetstream.

Personally I'd prefer the 6z solution with the Canadian PV lobe being 'drained' down towards us, as it then can interact with any subsequent incursion from the opposite side. The low the 12z spawns which trundles on disconnected doesn't really help in any constructive manner until it finds itself in the same position as the 06z system does at 252h. It's another option though.

The way it appears to be shaping up there may well be two or three sliders in a row, multiplying the drama! The last one possibly ‘draining’ the Canadian PV lobe or chased by a ridge being thown up behind it.

It looks implausible, it’s pushing through runner lows but disengages them so that it also tries to throw up a ridge. One or the other would be fine, neutralising the Azores high, but instead it tries to keep pushing it towards us.

As reported by GFS it’s actually pretty underwhelming. Much less so than the more active NW to SE slider. I’m not sure that wedge of heights does us any favours in that transition.

1035 Arctic high and suggestions of a sliding Atlantic low from NW to SE, showing elongation along that axis.

It’s become intolerable. Normally I don’t moan during summer on here (In return hoping that we are left to enjoy the cold in winter) but there are limits. I’m desperately trying to keep the heat out and my portable air conditioner is on overtime (although it can only really manage to get one room cooler). Tough times.

Turned to to rain. Still, pretty impressive for April and we’ll see how long the cover lasts. 2017/18 turned out pretty well for snow here in the end.

Still snowing heavily here after a number of hours (there was a nice covering by 6am, don’t know when it started). No signs of it stopping for another hour or two, everywhere white with a few inches or so. A lovely surprise, looks like Euro4 was on the money for here at least.

The GFS is a poorer outcome for all areas but misses the south and Scotland out regarding the major snow potential, leaving the midlands and the north as a favourable area. The better run for those areas was the 00z which was a much expanded area of instability, such as below. ICON still pretty good for the whole country at various times, though and the UKMO misses everybody!

The fog here is incredible, I can barely see the houses opposite and all the lights I usually see across the valley have disappeared completely. A real old fashioned pea souper! What with snow again this morning it’s been a great week for weather.

Met Office is showing until 3 or 4pm for this part of West Yorkshire.

Three possibilities - 1) we may get the north easterly edge of Storm Emma's main concentration of precipitation clip us around mid morning tomorrow. Looks less likely that it will get further east than the Pennines, if that. 2) the 'tail' of Storm Emma might hit the southern part of our area early on Saturday morning but most models have it petering out before, which would allow for..... 3) continued convective snowfall from the North Sea.into early Sunday, probably less powerful as Storm Emma interacts with it.

It’s been a classic day (two days really). Everywhere covered in inches of snow, including the roads. Icicles on my nearest lamppost glistening in its light. A few major whiteouts during the evening (when I can’t see the lights from across the valley you know there’s major snowfall). I hope that others elsewhere got at least some of this.

Halifax is more Brigg/Scunthorpe. The radar looks as though there may be some sort of streamer setting up! Epic morning so far, virtually non stop and with pulses of near whiteout conditions. Traffic very dodgy, all starting around 8am as the MetOffice suggested.

Correction- the actual knowledgeable posters have been quite non-committal and always issue caveats. There are some idiots who post rubbish like ‘feet of snow’, ‘blizzards across the country’ and such who are a real embarrassment though. More fool anyone who takes them at their word! They are easy to spot because they use words like feel, imagine, gut instinct and such, their meteorological knowledge is way behind their emotional incontinence! Probably a good job this isn’t the models thread!

Rather than start from the point of a preferred outcome, in this situation it’s best to go back to Sherlockian principles. “Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.". So, systems always travel west to east, right? Well, not if we have been put in reverse they don’t. Similarly that there is always a southwards movement of such systems as models zero in, well this is already only a two to one bet and, in these circumstances, it’s probably evens. So, all major models show the first low being sent north and west and this looks to be very likely now. GFS then traps the second low in the orbit of the first one, however, and they perform a slow circular dance whilst sending southerlies our way. Not a done deal in this instance because both UKMO and ECM have the next low escaping and being spun out at what may, or may not be a preferred angle. The further south the better but it all depends on how that second low behaves and when (or if) it escapes out to the east.

UKMO 144h 850s, the milder, rainier stuff in the south may turn out to be a 12/24 hour one, this time maintaining excellent 850s north of the M4 at least with the potential to have them dragged down southwards later.