The ECM and GFS 00z op runs paint an unfortunate picture for those wanting a good visit from the heat plume... but they're not representing any kind of consensus, with the model output as a whole in total disarray.

Two examples from the other end of the spectrum are UKMO and GEM 00z op runs:

The key difference is what happens with a trough in the jet stream between days 4 and 5.

ECM and GFS have this digging down toward the weak Iberian low, leading to the rapid development of an area of low pressure that sweeps northeast and sends the plume packing. High pressure is back on the scene very quickly but it's a fresher airmass with near average temperatures, soon rising on the ECM run but taking their time on the GFS run.

UKMO and GEM have a flatter jet which stays clear of the Iberian Low, a shallow depression heading north of the UK with a ridge to the south of it which keeps us settled and allows the plume to stick around to some extent. I say to some extent because northern parts of the UK end up being left out on the UKMO run. The GEM run warms things up for Scotland from Saturday onward.

A glance at the ECM ensemble spread suggests two distinct clusters, one with the LP development racing NE through or just NW of the UK, the other with the development some way SW of the UK, perhaps more like the GEM run:

It's likely that the position of the high pressure is having a fairly significant impact on the spreads as well. Overall it's a very uncertain picture for 5-6 days time.

Longer term, GFS has switched back to signalling a warmer regime but potentially unsettled at times, while ECM is a bit uncertain as of day 10, depending on how far east the incoming Atlantic ridge is able to get.

So very typical for CET prediction day 

It does look as though the core of heat is being shoved eastwards for Friday/Saturday...  

Yes, that really is a big pile of underwear isn't it?

And some people were seriously talking about 'the hottest June on record' just a couple of days ago.

Like your sig btw :)

Excellent as always James 

With regards to that upcoming warm spell, it is looking more and more like a blink and you'd miss it affair - but the general outlook beyond the weekend's thundery type weather (and even that needs to be firmed up) does look quite pleasant in nature - at least towards southern and eastern parts of the UK.
 
I think we should take on a less stressful pastime other than amateur meteorology as we drive ourselves nuts chasing shadows for most of the time.

Just as the media informs of high temps next weekend, the models show a downgrade with just a one day wonder here in the South East on Friday where temps could reach 80F, but with heavy thunderstorms to boot.
http://www.wetterzentrale.de/pics/Rtavn13217.gif
http://www.wetterzentrale.de/pics/Rtavn13211.gif

http://www.wetterzentrale.de/pics/Rtavn1321.gif

Warm and Thundery

GFS fi is

A mixed outlook and somewhat a little disappointing when compared to yesterday runs.

Interesting how a lot of the models were showing a more northerly \ northwesterly flow this morning for June in your excellent Summer forecast video Gavin. I wonder if that will be the story for June of one day hot spells that are short lived?

Warmer, then nearly back to where we are now.

From Friday huge disagreement.  Looks like the sort of ensemble chart 5 days out from a failed easterly.

yes huge split after just 5 days- it's knife edge and could go either way. The concern is that quite a few members return us to a wet and cool scenario- just what we have now. The talk of a few days ago about "hottest June on record" now looks a distant straw to clutch. 

Back to hibernation........

Have you never heard of the description of the British summer? "Three fine hours then a thunderstorm"? 

UKMO 120. not bad.

Edit - and 144 shows an intensifying HP over doc and a warm south easterly

Looking like a decent warm up then from Wednesday.

What could possibly go wrong

Appears the high temps have been delayed a couple of days into the early part of next week, though it doesn't last. Agree, there's so much change from run to run and quite what we'll get come the day.