Tell you what Richard; let's monitor this one. The scope of the "flash
warning of severe or extreme weather" forecast is this.

The headline for every area south of the border with Scotland and
north of a line from the Thames to mid-Wales is "Heavy rain". Not the
possibility of heavy rain, but a straight "Heavy rain". The site user
then has to go to their area where this is seen;

"Slow moving thunderstorms will develop this afternoon giving
torrential downpours and hail, although some places will miss them and
stay dry. However, in areas affected, 20-40mm of rain is likely in 3
hours or less. The public are advised to take extra care and refer to
the 'Highways Agency' for further advice on traffic disruption on
motorways and trunk roads".

Not "many" places will miss them, but "some" places will miss them and
stay dry. That clearly implies that most areas will get them. At
present, any user of the warnings site, living within the orange
coloured areas, would be expecting that they are likely to see heavy
rain, though they may miss out (not my use of the word "may"; that's
exactly what is implied by this warning).

There is no reference to the weather radar, which at 15.30 shows the
vast majority of the areas under the flash warning as dry, with a
probable N/S line of showers through East Yorkshire and Humberside
(light rain in Humberside C/O XC weather, some showers in the NW (XC
weather reported light rain at Blackpool airport at 1609) and a few
very isolated showers (OK possible, rain may not be reaching the
ground) over other areas. Instead the user is directed to the
highways agency site (no link). Presently, the highways agency has no
mentio of heavy rain that I can find. There are more organised bands
of rain across the SW and S Wales; these are outside of the flash
warning area and probably rightly so. We've had a few drops in
Dawlish.

I'm sure these showers will break out in other areas and there are
lots of reports of Cbs, but let's see if most people in those areas
get heavy rain. A difficult one to monitor exactly, I know, but let's
have a go.

I hope this is one of the good forecasts and the evening should
cartainly see some very lively weather for some as we get
destabilisation across the flash warning area. I'll give my judgement
at outcome. Would you like to do the same? Please correct me if I've
made errors in my summing up of the flash warning itself.