I've not been taking detailed looks at the ens but I'd assume just from the scatter that it's been an option for a while, so presumably a case of the Op picking this solution this time. 

Will wait for the ens to see how well supported this is, along with ECM, UKMO and GEM runs. 

The op run is definitely one of the milder options in the ensemble suite later in the run. By the 25th of November it is actually the mildest of all 30+ members for this location.

Cheers Michael. 

Acts as a cautionary note I guess but hopefully an unlikely outcome as it stands, ignoring the law of sod of course.

Static charts which this was generated from are here:

https://www.theweatheroutlook.com/twodata/gfs-hourly.aspx 

Some runs prolong the cold but both op and control follow each other to the mild breakdown (unlike the 06Z when both went cold).

Plenty of time to swing back yet but the UKMO looks pretty poor for cold too, with the cold air never really arriving in the south and the Atlantic ready to break through rapidly at T144.

On a more positive note the 12Z GEFS has the highest snow percentage yet for London at 35%.

Really?  T168 shows a channel low.

Has the channel low been replaced by the Brussels runner lol

UKVs take on who gets lying snow from Monday/Tuesdays system FWIW (not a lot at that range!).  Other than that the run shows a fairly stereotypical shower distribution for the set up, unsurprisingly. 

Not one that would give anything interesting though, and mild air rapidly piling in from the west courtesy of that big low in the Atlantic, from what I can see?

Met O and ECM look like little chance of anything properly wintry affecting the south, the blocking all heads into the continent with heights deserting Greenland. 

The first of no doubt many occasions this winter where the models go off one before crashing back to reality…

3c here on Monday and 2c for Tuesday according to the much maligned iPhone app!

https://modeles16.meteociel.fr/modeles/gensp/runs/2024111418/graphe3_10000_223_246___.gif 

We go from this at day 0 - an omega centred NW of the Azores:

...to this at day 10, the omega block having reformed over southern Greenland.

These are the "gold standard" blocks for cold fans, as they often repeat more than once - as we're seeing in the ECM run. The optimum position of the upper high is a bit further east than the 240 chart shows, but even so the UK is still under cold air on day 10.

One of these in the heart of winter would provide a memorable spell. At this time of year? Probably not, unless you have elevation, but that's the thing with marginal setups - you can often get unexpected snowfall locally, where just a few miles away it's cold rain.

Fascinating model watching, anyway, and I'll be very interested to see if other models can establish an omega block.

The iPhone app now has Wed, Thursday and Friday as the only cold[font=system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", "Noto Sans", "Liberation Sans", Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji"]ish days here (5C, 4C, 6C, with 0C overnight lows each night). 9C on Tuesday and back up to 11C by Friday. Zero precipitation on any of those colder days, either. [/font]

Very boring compared to the outlook a few days ago it must be said!

GFS Op 0z - has retreated from its ultra-cold predictions of a week ago. The N-lies set in on Sun 17th but mainly down the N Sea, not affecting W Britain, though they are souped up by a Channel runner reaching Dover 1000mb Tue 19th and another LP across N France 990mb Thu 21st. But all is cleared away by LP approaching from the SW and deepening markedly 960mb W Ireland Mon 25th, milder but not ultra-mild. This fills and slowly drifts across Britain to reach C Europe Sun 1st leaving a narrow ridge for HP behind.

ECM - the channel runner from the 19th merges with the main LP, 970mb Denmark Wed 20th ensuring a more consistent run of N-lies but even so the Atlantic revives from the SW Mon 25th, more tentatively than shown on GFS

GEM - resembles ECM. If anything the early N-lies on Sun 17th are held further east

GEFS - in the S, cold (5C below norm) 17th - 23rd with a mild blip coinciding with heavy rain on Tue 19th.  Heavy rain sets in later than shown yesterday, after Sat 23rd (but earlier in far SW), with the mean abruptly recovering to norm though conceals ens members from 5C below (incl control) to 10C above (incl op). Variation in the N is that the temp recovers to mean more slowly (very slowly in far N), and rain is less heavy at that time.

I like trying to outguess the weather with things like sliding shortwaves so the current situation is quite entertaining in a way but undoubtedly a headache for those who get paid to provide forecasts as somewhere at some point in the next 10 days will likely get a pasting. 

Longer term the GFS op doesn't go all in on an Atlantic return despite the T240 chart, with a colder flow eventually re-establishing after the LP gradually fizzles and we end up with a chilly/cold HP and a stalling Atlantic. Again some support for colder air re-establishing in the ens (or not leaving at all for a few) but equally plenty of mild runs, suggesting a not unexpected amount of uncertainty. 

No great surprise re the uncertainty in the mid to long term I guess but strong confidence in a noticeable cool down with a cold northerly flow establishing with some snow around biased to the North and higher ground as usual. Thereafter uncertain with a return to mild and wet entirely possible, as is a more prolonged chilly spell or a milder blip and something of a chilly reboot/reset. More runs needed and all that but enough interest in the near term to catch the eye, more so if you're towards the top half of the country rather than the bottom! 

Re Brian's UKV comment I find it's good at giving a general idea of rain and shower distribution but definitely agree it makes rain bands look much more fragmented than they are - the MetO generally seem to have the rain in the same area as the UKV chart but presumably add shading to make it clear the rain will be more of a block than the raw output would suggest. 

We are a bit elevated and sheltered so normally we get about 2 degrees less than what’s here.

Thats a pretty drastic switch. But well expected with these modern era northerlies.

Every thing delayed and shortened.

The switch is far more likely related to the data source being used.