This chart is simply bonkers... note these are 850s!

https://images.meteociel.fr/im/41/243/gens_0_0_312alk9.png 

Indeed it has 850s above 21c for a week (21st to 28th). Top end of the ensembles as you would expect. 

The Control in the 6z is loopy. 5 days of 35+ forecast here, with a string of Thames Valley 40s on one day.

Thought for a minute I had a 38 there, but upon looking more closely it's 'only' a 36. 

But that would still put this area into July 2022 territory.

I see nobody has yet stuck their head above the parapet and started a 'Late June Heatwave' thread yet.

Perhaps you should do it in order to scupper it 🙂

I remember August 2003, being impressed with one day of the same (and a small zone of 576dam, which we exceed also in this model).

Another record casually broken were it to come off - the 12z GFS brings 576dam thicknesses over Kent at T+150, well in excess of anything previously recorded in June:

https://max.nwstatic.co.uk/gfsimages/gfs.20260615/12/150/hgt500-1000.png 

https://web.archive.org/web/20030310024855/http://www.booty.demon.co.uk/tthkxtrm.htm 

I remember 25 years ago when everyone got exited about the 564 line... how times change!

Looks like 578dam. Insane. 

Hadn't realised there were thickness charts on TWO for GFS - handy! 👍And yes, 578 in June is utterly bonkers. That's my word of the extended summer this year, I think!

Many years ago, around the turn of the millennium, a younger me asked on usw whether it was physically possible to get the 582 line over the UK (being the next step up from 564 - the old WZ charts went 474, 492, 510, 528, 546, 564, 582, and that was chosen based on the even older hand-drawn charts). The replies came in that we couldn't get anywhere near it, I think people found it mildly amusing that anyone should ask! Yet here we are, getting perilously close to seeing it. I suspect we *will* see it in the next 25 years, the way we're going, and I also suspect we'll never see the 492 line again in any of our lifetimes, or maybe even sub-500 (according to that thickness link from booty that I posted, the record low is 491 near Shetland. I know it was darned close to 492 here in 1987 too).

Yes, it has a straighter upstream jet and introduces a northerly feed by Monday, albeit an anticyclonic northerly - it's maritime air. It's joined in that by the new GEM, though ECM shows 20C+ 850s over the far SE still on Monday. 

I remember this place in 2003 when the 20C 850s made a glancing blow. It felt unprecedented now it seems to happened with increasing regularity 

The heat in France looks historic multiple 40c + days. The merest waft our way and we'll break the June record.  

The operational delivers a 39C as a peak, with 35C on Monday.

What is remarkable is that temps remain high for the majority of the run and we get wafts of more extreme heat. 

Indeed. The spread on the GFS erks a little, but even then above average throughout the run.