Are you looking at the 00z data?

Uppers seem cooler on this run

Marginally cooler uppers perhaps, but heat sets in earlier and lasts throughout Saturday at least.

Was always looking like a short lived affair, but no major downgrade as far as I can see.

GFS 06z has 35C on Friday.

The extended is a country mile different to yesterday's 6z too.
Gone is deep Autumnal low and replaced with a strengthening Azores High.
Everything is uncertain at the moment, including the level and longevity of any heat spike.
I think ex-TS Alex is playing havoc with the models.

That might work in favor to re-shuffle the pattern which had been locked in for months that gave us very poor cold Spring to very warm side for the summer I hope.

Spring was warmer than average for every month. You’ve stated before that it was cold and it was wrong then too. Both the mean temperature and the daily max were above the long term averages,

An above-average hurricane season has been forecast by all the major players so long-term summer forecasts (bets?) on the Atlantic weather are definitely risky

Very warm London from Tuesday then Hot perhaps V Hot best mid term best set of the summer thus far

https://www.meteociel.fr/modeles/gefs_table.php?x=0&y=0&lat=51.5085&lon=-0.12574&run=12&ext=1&mode=7&sort=0

fab ukmo 120 144

https://www.meteociel.fr/modeles/ukmo2.php?nh=0&ech=120&carte=1021

https://www.meteociel.fr/modeles/ukmo2.php?ech=6&carte=1021

168

https://www.meteociel.fr/modeles/ukmoeu.php

Great post. Very factual and interesting. Surprised to hear that, but 13 is an unlucky number etc etc

several UK locations should be topping 30c by Friday, if not before. 

Dangerous and extensive heat in France on Friday 

https://www.meteociel.fr/modeles/gfs/temperatures-2m/144h.htm

Hardly a heatwave setting in. It may be like a one night stand,enjoy it while  it lasts for a whole 36-48hrs.

Having just watched Gavin P`s latest 10-14 dayer there is one model having none of this heat spike, ICON, remember this is the model that went against the grain pre xmas when all others were nailed for cold. We shall see. One thing is for sure the following week will temperatures fall off a cliff especiallyin the north with the 0c isotherm covering most of scotland. This is turning out to be a very interesting month.

Is this the same ICON that went for a white Christmas? 
We are pretty much nailed on for consecutive hottest day of the year for about 4 days. What happens after that is conjecture at this stage. I’d expect more enthusiasm from someone living on the south coast. 

No I think ICON was the one that did not go for a white Xmas when all the other models at one point were going for it. So we shall see how it does with this...

I'm pretty sure it never went for it in the first place so people started praising it as some kind of super model that had outdone the big boys. But I'm sure that was more down to luck than anything...

Yep there were plenty of other occasions where it has embarrassed itself very short term but the moral of the story is that if one model is sticking to it guns against the mainstream there should be low confidence and you would be a fool to discount anything. 

The heat wave has been reduced in length and intensity

https://www.meteociel.fr/modeles/gfs/temperatures-2m/180h.htm (thanks to PL) GFS shows very hot temps in SW France on Thu spreading to the whole country on Fri with 40C as far north as the Loire valley at 1400 - but those temps were more widespread yesterday - and they move off to Germany on Sat. By Sun the Loire valley is down to 11C at 1400.

In the UK, the London basin reaches 25C on Thu then 31C on Fri - but not the 35C touted earlier - and on Sat only the far south is still in the 20s. The northward extent of the extra warmth now seems confined to England with E Scotland now merely normal.

For the longer term, WX summary shows the hot weather spreading up through France to Germany and touching England week 1 (and modestly warm further east) but in week 2 the cool weather has moved back down from N Scotland and Norway quite far S into Germany. At the same time warm weather is still there in SW France with a chance of returning to S Britain - but the 0C isotherm makes an appearance in Iceland! Dry-ish from the SW across UK to the Baltic with rain around the edges of this area, and some further E around the Black Sea

Jet appearing irregularly near N Scotland, more persistent and further N later

GFS Op - HP ridging in from the SW to 1020mb England Thu 16th then slipping E as LP 1000mb moves to Orkney Sun 19th with associated trough dipping a long way south and N-lies all the way down to Spain. New large area of HP then moves E wards from the Atlantic and although never centred over Britain has sufficient strength to keep the LP over Scandinavia at a distance, and to bring what looks like mild/warm w-lies across UK for the following week (what I would call pleasantly usable summer weather)

GEFS - in the S rising briefly to hot Fri 17th then mean temp back down to close to norm for an extended period; dry to 18th then small amounts of rain. In the N, warm but not not on Fri, otherwise similar (though the Op run is a warm outlier for all of week 2)

ECM - similar to GFS to Sat 18th but then throws in a significant Channel low as part of the breakdown on sunday; it blocks the N-ly run of winds but introduces some unsettled weather for the S coast. At time of posting Mon 20th onwards is still 12z and while the chart resembles GFS, the HP is further S so may be cooler and damper in W Scotland. [may get edited after I've had breakfast] -indeed needs editing - the Channel low deepens 995mb Cornwall Mon 20th and proceeds to link up with a trough from Iceland covering the whole of UK with cold and unsettled weather. No sign of Hp and quite different to GFS

Thanks Dew much appreciated.

Friday seems like the hot day a max temp of 32c to 35c looking possible this morning.  

ECM almost prolongs the heat this morning but gets very messy. 

The few gfs members that extended the heat into Saturday are very hot indeed Per1 with 24 uppers into s/e given as 36.3C easily add a couple on so all time ukrecorded under threat if that came off in the minority I know but worthy of note for hot weather freaks and ever closer to a 40c for the U.K.  

https://www.meteociel.fr/modeles/gefs_table.php?x=0&y=0&lat=51.5085&lon=-0.12574&run=0&ext=1&mode=7&sort=0

https://www.meteociel.fr/modeles/gefs_cartes.php?code=1&ech=150&mode=0&carte=0&ext=0